Ajs Classic 1945 1957 OHV Touring Singles Pitmans, 1945 1957 AJS Pitmans book of the Ajs 1945 1957 AJS Pitmans book of the

PITMAN' S MOTOR -CYCLISTS' LIBRARY

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The Book of the

A.J.S.

A PRACTICAL GUIDE ON THE HANDLING

AND MAINTENANCE OF ALL 1945-57 O.H.V.

TOURING SINGLES

BY

W.C.HAYCRAFT

F.R.S.A.

EIGHTH EDITION

LONDON

SIR ISAAC PITMAN & SONS, LTD.

PREFACE

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MY first practical experience with an A.J.S. was in 1927 when 1 bought a "big port"
O.H.V. 350 c.c. model. Even then A.J.S. performance was very high. Today A.J.S.
motor-cycles have a world-wide reputation for high performance, mechanical
quietness, reliability, and economical running. Appearance and general finish too
are excellent.
It has always been, and still is, the policy of A.J.S. Motor Cycles of Plumstead
Road, London, S.E.18, to develop and perfect their machines gradually, and to
embody in the standard touring models their experience gained through participation
in racing and trials events.
As hitherto, the object of this handbook is to help you to obtain the maximum
pleasure, mileage, m.p.h., m.p.g., and m.p.£ from your mount, and to reduce
depreciation to the minimum.
If you have never before handled an A.J.S., turn direct to Chapter 1 which deals with
preliminaries, starting-up, gear changing, running-in, etc. A useful book for novices
(and experienced riders) is The Art of Motor Cycling, published by Pitman at 5 s. The
remaining chapters deal comprehensively with the maintenance and overhaul, of the
following fourstroke O.H.V. single-cylinder touring models-

1. The 1945-55 347 c.c. rigid-frame Model 16M.

2. The 1945-55 498 c.c. rigid-frame Model 18.

3. The 1949-57 347 c.c. spring-frame Model 16MS.

4. The 1949-57 498 c.c. spring-frame Model 18S.

Except where otherwise stated, the instructions given apply to 1945-57 inclusive.
Machines not covered in this handbook are: the Trials models, the Scrambles
models, the overhead-camshaft racing models, and the twin-cylinder O.H.V. touring
machines. The competition models, by the way, have engines similar to the touring
models dealt with in this handbook, but they have, of course, specialized equipment.
In conclusion I thank A.J.S. Motor Cycles (and various accessory firms) for their
kindness in providing technical data, and for according me permission to reproduce
many copyright illustrations.

W.C.H.

CONTENTS

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CHAP. Page

I. HANDLING AN A.J.S.................................................................1

Essential preliminaries-Starting the engine-Gear changing
General driving hints

II. ALL ABOUT CARBURATION...............................................11

Amal standard carburettor-Amal "Monobloc" carburettor
Tuning Amal carburettor-Carburettor maintenance-
The air filter

III. THE LIGHTING SYSTEM......................................................24

Illumination-The lamps (1945-8 models)-The lamps (1949
onwards)-Maintenance of battery-Maintenance of dynamo­The horn-The wiring system

IV. CORRECT LUBRICATION......................................................48

Engine lubrication-Motor-cycle lubrication

V. GENERAL MAINTENANCE....................................................70

Engine maintenance-The ignition system-Diagnosing ignition
faults-Tappet adjustment-Decarbonizing and valve grinding­Valve timing-Complete engine overhaul-Motor-cycle main­tenance-Tyres-Brakes-The transmission-The frame
Wheels-Miscellaneous

Index.................................................................................................. 145

CHAPTER I

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HANDLING AN A.J.S.

AN A.J.S. O.H.V. single is easy to handle, and even the absolute novice quickly
acquires confidence in the saddle. Beware, however, that you do not indulge in big
throttle openings until you have had ample road experience. Also do not forget to
digest the Highway Code.

FIG. 1. A FLEXIBLE AND FAST TOURER WITH CLEAN LINES AND ME CHANICAL QU IETNESS ­THE 1957 MODEL 18S

The 500 c.c. A.J.S. model shown is similar to the 35 0 c.c. model 16MS. Both models have s nappy push rod
O.H.V. engines with light-alloy cylinder heads, "Monobloc" carburettors, hairpin valve-springs, and
automatic-ignition control. Their specification includes: "Teledraulic" front forks, Girling rear-suspension units,
a quickly detachable rear wheel, die-cast light-alloy hubs , a deep secondary-chain guard, a new A.M.C. four­speed gearbox, Lucas headlamp, twin pilot-lights, and other attractive features.

* The A.J.S. engine and frame numbers required on Form R.F. 1/2 will be found on the near-side of the
crankcase and the off-side of the saddle lug, or on the off-side of the front down-tube (later models).

Essential Preliminaries. Before you can legally ride on the road -

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(1) Insure against all third-party risks and obtain the vital "certificate of
insurance."
With a new machine you cannot get this until the machine is licensed, and an
insurance "cover note" must be obtained. If you have a valuable machine, you are
advised to take out full comprehensive insurance.
(2) Obtain the registration licence and registration book (Form R.F.I/2)* or renew
the licence (Form R.F. I/A).
(3) Obtain a three-monthly "provisional" or an annual driving licence
(Form D.L.I).*
(4) Fit a reliable speedometer if one is not fitted (not essential if machine
registered prior to 1st Oct., 1937).
(5) If you carry a pillion-passenger, see that he or she sits astride a proper pillion
seat securely fixed to the machine (all "springers" have dualseats), and that the
passenger holds a current annual or substantive driving licence for Group G if you
are a "learner."
(6) If you are ineligible for an annual or substantive driving licence, attach "L"
plates to the front and back of the machine.
(7) If not already provided, fit a red reflector (1½ in. minimum diameter)
vertically at the rear of the motor-cycle and, on a sidecar outfit, an additional red
reflector and rear lamp at the rear of the sidecar and at the same height as those on
the motor-cycle.
(8) Use an ignition-suppression type sparking plug or terminal cover if the
machine was registered for the first time after 1. st July, 1953.
All the official forms referred to above may be obtained from any money-order post
office. See also footnote **, with reference to Forms R.F, 1/A or R.F. 112.
You are not eligible for a substantive driving licence for Group G unless you are 16
and have complied with one of these conditions-
(a) You have held a licence (other than a provisional or Visitor's licence
authorizing the driving of vehicles of the class or description applied for within a
period of ten years ending on the date of coming into force of the licence applied
for.
(b) You have passed the prescribed driving test (this includes a test passed while
serving in H.M. Forces) during the said period of ten years.

* Recent legislation provides for a six-month's provisional licence, and a substantive driving licence

valid for three years.

** Models 18S and 16MS are taxed at £3 15s. per annum, with £1 5s. extra duty for a sidecar.

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FIG. 2. LAYOUT OF HANDLEBAR CONTROLS (1945-53 MODELS)
This also applies to the 1954 350 C.C. models, which have manual ignition control. All cont rols operate by

inward movement and the handlebar clips are adjus table for angle. l ie dippin g switch (not sh own) is mounted
close to the ignition control. At A are shown th e filler plu g s for the fron t fork s.

FIG. 3. LAYOUT OF HANDLEBAR CONTROLS (1954 ONWARDS)
Automatic ignition-advance mechanism was no t fitted to th e 1954 35 0 c.c. mo de l, and this h ad manual

ignition control as shown in Fig. 2. As hitherto all controls are adjustable for angle and are operated by inward
movement. Prior to 1955 the ammeter, lighting switch an d speedometer were positioned as shown In Fig. 2.
1956-7 models have a combined dipping-switch and horn push.

STARTING THE ENGINE

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First verify that there is sufficient petrol and oil in the tanks. Handlebar controls are
shown in Figs. 2, 3; oil tank and gearbox replenishment are dealt with on pages 53
and 60 respectively. Check that the gear-change pedal is in neutral (see Figs. 5-7).

Adjusting the Controls. If the engine is cold -
(1) Set the throttle so that it is slightly open by turning the twist-grip inwards about
one-sixth of its total movement.
(2) Completely close the air-control lever.
(3) Fully advance the ignition-control lever (where fitted) by pushing it outwards to

its full extent, and then retard it by about two-fifths of its total movement by pulling it
inwards. 1945-52 models: pull inwards to advance.

If the engine is already warm, open the throttle about a quarter and the air-control
lever half to three-quarters.

The Petrol Tank Filler Cap. Some riders find that the filler cap does not come
away instantly. On A.J.S, machines, to release the filler cap quickly, depress it
slightly, then turn it fully anti-clockwise and withdraw the cap. It has two locking
positions.

Main and Reserve Petrol Taps. Many A.J.S. singles have down-draught type
Amal carburettors and on such machines it is important when leaving a machine
standing for more than a few minutes always to turn off both the main and reserve­supply petrol taps.
Both taps are of the horizontal-plunger type. To open (1945-54), push the hexagon
knob marked PUSH-ON towards the tap body. To shut the tap push the knurled
knob marked PUSH-OFF towards the tap body. As mentioned in a later paragraph,
it is advisable no rmally to r un with only t he off-side t ap open. Refuelling should be
undertaken as soon as possible after being forced to draw upon the reserve-fuel
supply. The reserve supply tap should then be shut immediately. On 1955 and later
models, to close either tap, push the plunger right in; to open it, pull the plunger
right out.

If Engine is Cold. If the engine (especially a new one) is stone cold, it is generally
advisable to free the piston before attempting to start up. Raise the exhaust-valve
lifter and kick the engine over smartly about three times.

Starting Procedure. After setting the controls, depress the float chamber "tickler"
momentarily, but do not flood the carburettor so that petrol drips from it. It is
assumed that the petrol has been turned on by using the off-side tap. Use the other to
maintain a reserve supply. Turn the engine ov er slowly with the kick-st arter pedal
until the resistance of compression is felt.

Raise the exhaust-valve lifter and allow the piston just to pass the position of full

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compression. Then allow the kickstarter pedal to return almost to its normal
position. Release the exhaust-valve lifter and simultaneously kick the engine over
sharply with along swinging kick. If nothing happens, repeat the procedure until it
does! When the engine fires, open the air-control lever slowly, advance the ignition
and open the throttle slightly to give even running on the pilot jet. Check the oil
circulation (see page 53).

Avoid Force on Kick-starter Pedal. It is very important not to exert excessive
force on the kick-starter pedal (see Fig. 4) until the toothed quadrant (A) has moved
in the direction of the arrow sufficiently to bridge the gap (C) between the quadrant
and the kick-starter ratchet pinion (B).
Until the gap (C) has been bridged and full engagement has been obtained and felt, a
slow, gentle operation of the kick-starter is essential to prevent wear and da mage.
Never use excessive force.

Excessive Flooding is Risky. Do not adopt the pernicious habit of swamping the
carburettor with petrol before starting up. Such flooding incurs a grave risk of neat
petrol entering the cylinder from a downdraught carburettor and destroying the vital
oil film between the piston and cylinder.

If Engine Refuses to Start. If the engine
refuses to start at the third kick, verify that
petrol is reaching the float chamber by
depressing the tickler. When you are satisfied
on this point, remove and carefully inspect
the sparking plug. Clean the plug, check its
gap, and replace it (see pages 73-5).

Correct Method of Warming Up.

Do not race the engine immediately after
starting up from cold, as it takes some time
for the oil to circulate properly. Running the
engine too fast also generates excessive heat.
On the other hand, do not warm up the
engine too slowly, or the pump will not work
fast enough to circulate the oil properly and
the combustion of a rather cold mixture will
be incomplete, with the result that
condensation on and corrosion of the
cylinder walls may occur.
Never allow the engine to idle for long,
especially i n hot weather, and do not t ravel fast until the oil has warmed up.

FIG. 4. THE KICK-STARTE R (1945-1951 )
A, B, C SHOW THE QUADRANT, RATCHET PIN ION,

AND THE GAP BETWEEN THEM, RESPECTIVELY.

D IS THE QUADRANT STOP.

GEAR CHANGING

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Ease the A.J.S. off its stand, with the engine ticking over and the foot gear-change
pedal in neutral, sit astride the machine, and disengage the clutch, using the
handlebar lever (see Figs. 2, 3).

FIG. 5. THE FOOT GEAR-CHANGE INDICATOR (1945-51 MODELS)
All changes up to a higher gear are made by depressing the pedal with the toe. and all changes down to a lower

gear by raising the pedal with the toe. Internal spring' return the pedal to the horizontal position after each gear
change is made.

FIG. 6. THE FOOT GEAR-CHANGE INDICATOR (1952-6 MODELS)
The indicator itself comprises a small drum having the gear positions marked as shown. N (neutral) is shown

aligned with the dash mark on the gearbox shell.

Engaging First Gear. Raise the foot gear-change pedal fully with the toe of the

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foot and engage first (bottom) gear (see Figs. 5-7). Slight backward or forward
movement of the machine often facilitates engagemerit. As soon as first gear is felt
to engage, remove the toe from the pedal. If difficulty is experienced in engaging
first gear, wait a few seconds before making another attempt. Initial difficulty in
engaging first gear on a new machine usually cures itself quite soon, and sticking
clutch-plates can be rectified by stopping the engine (by raising the exhaust-valve
lifter) and smartly operating the kick-starter several times with the clutch fully
disengaged.
To Move Off. Having engaged first gear, move off by slowly releasing the clutch
lever. As the machine gathers speed and the engine takes the full load, gradually
increase the throttle opening by means of the twist grip, so as to maintain a
progressive rise in the speed of the engine and machine.

Changing Up (First to Second). As soon as your A.J.S. has reached a speed of
about twelve m.p.h. in first gear, change up into second gear. Once again disengage
the clutch, slightly close the throttle, pause a second, and then depress the gear­change pedal to its full extent with the toe, until second gear is felt to engage
perfect ly. Then engage the clu tch and also remove the toe from the pedal to allow
the pedal to return to its normal position.

FIG. 7. THE FOOT GEAR-CHANGE INDICATOR (1957 MODELS)
The indicator comprises a pointer on the gear-change lever shaft, and a marked quadrant on the gearbox.

Changing Up (to Third and Fourth). Progressively increase the throttle opening

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until about twenty m.p.h. is obtained. Now disengage the clutch, throttle down
slightly, pause a second, and then smartly, but without force, depress the gear­change pedal fully until third gear is felt to engage perfectly. Engage the clutch,
remove the toe from the pedal, and throttle up to maintain a good road speed
without any tendency for the engine to "knock." To change into fourth (i.e. top gear)
repeat the procedure at nearly thirty m.p.h.

To Change Down (Fourth to Third). Throttle down to a normal speed for third
gear. Disengage the clutch, throttle up slightly, pause a second, and raise the gear­change pedal to its full extent with the toe of the foot until third gear is felt to
engage. Immediately afterwards engage the clutch, remove the toe from the pedal,
and throttle up to compensate for the increase in the speed of the engine relative to
rear-wheel speed.

To Change Down (to Second and First). The req uired proc edure is similar to
that just described for changing down from fourth to third gear. With the toe of the
foot raise the gear-change pedal to its full extent during each gear change. Each full
movement of the pedal engages the next gear in the gear-change sequence as shown
by the indicator in Figs. 5-7.
To change from fourth or third gear into first (bottom) gear, it is not essential to
complete the full gear-changing procedure for each intermediate gear, although this
should be done when hill climbing. The method which can be used is to bring the
machine to a crawl by means of the throttle and brakes, disengage the clutch, and
then raise the gear-change pedal to its full extent-three times or twice (in quick
succession), according to whether top or third gear was previously engaged. Each
time you raise the gear-change pedal "blip" the engine, i.e. throttle up slightly. Then
gently re-engage the clutch.

Silence Is Golden. Noisy gear changing is bad for sensitive cars, and worse still
for the gearbox! Learn to change gear silently. Here are a few golden rules-
(1) Make full use of the four gear-ratios provided. The gear-change pedal always
returns to the same position, but do not forget where it is.
(2) Do not "bully" the machine up a steep incline in top gear.
(3) Change gear before your mount gets "hot and bothered."
(4) Use a nicely coordinated and almost simultaneous movement when operatin g the
clutch, throttle, and gear-change pedal.
(5) Keep a steady pressure on the gear-change pedal and hold the clutch out until
the gear is felt to engage. At other times remove the foot.
(6) Do not race the engine in the lower gears to "impress the lads." They may like
it (perhaps) but your engine will hate you!
(7) Be kind to the gearbox and give it its oil ration occasionally (see page 60).

Negotiating Hills. Your A.J.S. will romp up gentle gradients, but maintain the

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engine r.p.m. high by making full use of the gearbox where necessary and in good
time. On no account permit the engine to labour. Be liberal with the throttle

opening, and do not retard the ignition-control lever (where fitted) unless this is
essential (to ward off a "knock"), as this reduces power output.
When descending steep hills, open the air lever wide and close the throttle. This will
not only cool the engine, but it will enable engine compression to exert a powerful
braking effect.

Use of Brakes. Acquire the habit of using both brakes simultaneously, as this gives
powerful braking with minimum and even wear of the brake linings and tyres.
Excessive and fierce brake application plays havoc with the tyres and transmission,
and for this reason you should learn to drive on the throttle and use the brakes as
little and as seldom as possible. Make use of engine compression as a brake when
descending hills (see previous paragraph), but never use the clutch or exhaust-valve
lifter for controlling speed. This places a motor-cyclist beyond the pale.

To Stop the Machine. To effect a normal stop on the road, use the following
procedure-
(1) Close the throttle by means of the twist-grip.
(2) Fully disengage the clutch.
(3) Apply both brakes simultaneously, increasing the hand and fo ot pressure as the
brakes take effect.
(4) Raise the gear-change pedal fully once or several times (according to which gear
is already engaged) until you get into first gear. Then depress the pedal very slightly
with the toe until "neutral" (see Figs. 5-7) is obtained.
(5) Engage the clutch by gently releasing the lever.

To Stop the Engine. After bringing the motor-cycle to a halt with the throttle
closed (as far as the throttle-stop permits*), it is only necessary to raise the exhaust­valve lifter for a few seconds in order to extinguish all signs of life. Before you leave
your machine, turn off the petrol tap to prevent accidental "flooding."

* The correct throttle-stop setting is such that when the eng ine is warmed up and the thro ttle is closed, the engine
ticks over smoothly (see page 17).

Running-in New Machine. On covering 1,000 miles it is not harmful to step up

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the speed of a new machine gradually, but refrain from using full throttle until about
2,000 miles have been covered. A new A.J.S. must be properly run-in, or it may be
permanently spoiled.

Here is some sound advice-
(1) Don't exceed one-third full throttle for 1,000 miles.
(2) Don't "over-rev." the engine when idling or on the road, especially in the lower
gears.
(3) Don't often exceed 30 m.p.h. in top gear.
(4) Don't permit the engine to labour or "knock." Change down in good time.
(5) Don't run the engine with the machine stationary for more than a minute or two.
(6) Don't forget to keep the engine, gearbox, and machine correctly lubricated (see
Chapter IV).
It is beneficial during the running-in period to mix one pint of Acheson's Colloidal
Graphite with each gallon of engine oil. This benefits the cylinder and bearing
surfaces. If the compound (obtainable from most garages) is used after running-in,
reduce the amount by one half.

After Covering 400-500 Miles. A certain amount of beddin g-down occurs, and it
is important to check the adjustment of the following: (a) tappets, (b) contact­breaker points, (c) steering head bearings, (d) primary and secondary chains, and (e)
brakes. Steering-head bearing adjustment is very important, as slack bearings will
suffer. After the initial bedding-down and necessary adjustments have been made,
further adjustment is needed much less frequently.

CHAPTER II

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ALL ABOUT CARBURATION

A STANDARD type Amal needle-jet carburettor is fitted to all 1945-54 single­cylinder 350 c.c. and 500 c.c. A.J.S. engines but all 1955 and later engines have the
"Monobloc" type Amal needle-jet carburettor fitted.

AMAL STANDARD CARBURETTOR

An understanding of the working of the standard Amal carburettor is desirable
before considering its tuning and maintenance. Referring to Fig. 8, showing a
sectional view of the Amal semi-automatic carburettor, (A) is the carburettor body
or mixing chamber, the upper part of which has a throttle valve (B), with taper
needle (C) attached by a needle clip. The throttle valve regulates the quantity of
mixture supplied to the engine. Passing through the throttle valve is the air valve
(D), independently operated and serving the purpose of obstructing the main air­passage for starting and mixture regulation. Fixed to the underside of the mixing
chamber by the union nut (E) is the jet block (F), and interposed between them is a
fibre washer to ensure a petrol-tight joint.
On the upper part of the block is the jet-block barrel (H), fornding a clean
through-way. Integral with the jet block is the pilot jet (J), supplied through the
passage (K). The adjustable pilot-air intake (L) communicates with a chamber, from
which issues the pilot outlet (M) and the by-pass (N). A throttle stop (see Fig. 9) is
provided on the mixing chamber, by which the position of the throttle valve for tick­over is regulated independently of the cable adjustment.
The needle jet (O) is screwed in the underside of the jet block, and carries at its
bottom end the main jet (P). Both these jets are removable when the jet plug (Q),
which bolts the mixing chamber and the float chamber together, is removed. The
float chamber, which has bottom feed, consists of a cup (R) fed with petrol through
union (S). It contains the float (7) and the needle valve (U) attached by the clip (V).
The float chamber cover (W) has a lock screw (X) for security.
The petrol tap having been turned on, petrol will flow past the needle valve (U)
until the quantity of petrol in the chamber (R) is sufficient to raise the float (T),
when the needle valve (U) will prevent a further supply entering the float chamber
until some in the chamber has already been used up by the engine. The float
chamber having filled to its correct level, the fuel passes along the passages through
the diagonal holes in the jet plug (Q), when it will be in communication with the
main jet (P) and the pilot feedhole (K); the level in the needle and pilot jets being,
obviously, the same as that maintained in the float chamber.

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FIG. 8. SECTIONAL VIEW OF AMAL STANDARD NEEDLE-JET
CARBURETTOR FITTED TO ALL 1945-54-MODELS

Imagine the throttle valve (B) very slightly open. As the piston descends, a partial

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vacuum is created in the carburettor, causing a rush of air through the pilot-air hole
(L) and drawing fuel from the pilot jet (J). The mixture of air and fuel is admitted to
the engine through the pilot outlet (M) which has a pilot-air screw adjustment (see
Fig. 9), used in conjunction with the throttle-stop screw to obtain a good slow­running mixture. The quantity of mixture capable of being passed by the pilot outlet
(M) is insufficient to run the engine. This mixture also carries excess of fuel.
Consequently, before a combustible mixture is admitted, throttle valve (B) must be
slightly raised, admitting further air from the main air-intake.
The farther the throttle valve is opened, the less will be the
depression on the outlet (M), but, in turn, a higher depression
will be created on the by-pass (N), and the pilot mixture will
flow from this passage as well as from the outlet (M). The
mixture supplied by the pilot and by-pass system is
supplemented at about one-eighth throttle by fuel from the
main jet (P), the throttle valve cut-away determining the
mixture strength from here to one-quarter throttle.
Proceeding up the throttle range, mixture control by the
needle position occurs from one-quarter to threequarters
throttle, and from this point the mainjet is the only
regulation. The air valve (D), which is cable-operated like
the throttle valve, has the effect of obstructing the main
through-way and, in consequence, increasing the depression
on the mainjet, enriching the mixture. Two cable adjusters
(G), (G1), are provided.

FIG. 9. THROTTLE
STOP AND PILOT-

AMAL "MONOBLOC" CARBURETTOR

The Amal "Monobloc" carburettor specified on all 1955 and later A.J.S. O.H.V.
singles differs from the standard type, used before 1955, in several respects. But its
general functioning is similar. The "Monobloc" design includes: a horizontal float
chamber made integral with the carburettor body; a float needle of moulded nylon; a
top Petrol-feed; a needle jet with bleed holes giving two-way compensation; and a
detachable pilot-jet which can be easily cleaned.
Fig. 10 shows all the essential parts of the instrument. The float chamber (13)
and needle (9) maintain a constant level of petrel in the needle jet (14) and the pilot
jet (17). The selection by the makers of the appropriate jet sizes and main-bore
choke ensures a proper atomizing and proportioning of the petrol and air sucked into
the engine. The air valve (3) is normally kept fully raised, and the throttle valve (24)
is controlled by the handlebar twist-grip controls the volume of mixture, and
therefore the power. At all throttle openings a correct mixture is automatically
obtained.

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FIG. 10. AMAL "MONOBLOC" CARBURETTOR (1955 ONWARDS)
SHOWN DISMANTLED

The "Monobloc" carburettor, like the standard instrument, operates in four stages.

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When opening the throttle from the fully closed position to one-eighth open (for
tick-over) the mixture is supplied by the pilot jet (17), and the strength of the
mixture is determined by the setting of the knurled pilot-air adjusting screw (20)
which has a coil locking-spring to facilitate adjustment. As the throttle is opened
slightly farther, the main jet system comes into action, the mixture being augmented
by the main jet (16) through the pilot by-pass.

The amount of cut-away on the atmospheric side of the throttle valve regulates the
petrol-to-air ratio between one-eighth and one-quarter throttle. The needle jet (14)
and the jet needle (23) take over the mixture regulation between one-quarter and
three-quarter throttle, and the mixture strength is determined by the relative position
of the needle in the clip (4) attached to the throttle valve (24). When the throttle is
opened beyond three-quarters, the mixture strength is determined only by the size of
the main jet. Note that the main jet (16) does not spray petrol direct into the
carburettor mixing-chamber, but discharges through the needle jet into the primary
air-chamber. From there it enters the main choke through the primary air-choke.
The latter has a two-way compensating action in conjunction with the "bleed" holes
in the needle jet. Pilot and main jet behaviour are not affected by this two-way
compensation which governs only acceleration at normal cruising speed.

TUNING AMAL CARBURETTOR (STANDARD AND "MONOBLOC"
TYPES)

The same tuning instructions apply to the standard and "Monobloc" instruments.
Normally it is unwise to interfere with the maker's carburettor setting (see Tables I­III) unless there is a very special reason for doing so. However, it is sometimes
desirable to make a slow-running adjustment with the pilot adjusting-screw and
throttle-stop screw.

KEY TO FIG. 10

1. Mixing-chamber cap. 14. Needle jet.

2. Mixing-chamber cap ring. 15. Main-jet holder.

3. Air valve 16. Main jet.

4. Jet-needle clip. 17. Pilot jet.

5. Jet block. 18. Throttle-stop adjusting screw.

6. Air passage to pilot jet. 19. Jet-block locating screw.

7. Tickler assembly. 20. Pilot-air adjusting screw.

8. Banjo securing-bolt. 21. Mixing chamber.

9. Float needle. 22. Fibre seal.

10. Float. 23. Jet needle.

11. Float-chamber cover screws. 24. Throttle valve.

12. Float-chamber cover. 25. Throttle return-spring.

13. Float chamber.

TABLE 1

n

n

n

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Model Car- Mai
350 c.c. O.H.V. 76AE/1AK 150 130 6/4 3*

500 c.c. O.H.V. 89B/1AK 180 160 29/4 2

Model Carburettor Mai
350 c.c. O.H.V.

(no air filter) 376/5 210 30 376/3 3
350 c.c. O.H.V
(with air filter) 376/33 200 30 376/3 3
500 c.c. O.H.V.
(to engine 27000) 376/4 240 30 376/3 2
500 c.c. O.H.V.
(after No. 27000) 389/1 260 30 389/3 3

AMAL CARBURETTOR SETTINGS FOR 1945-54 SINGLES

With Air Throttle Needle

burettor Jet Filter Valve Position

TABLE II

AMAL CARBURETTOR SETTINGS FOR 1955-56 SINGLES

Pilot Throttle Needle

Jet Position Valve Jet

TABLE III

AMAL CARBURETTOR SETTINGS FOR 1957 SINGLES

Model Carburettor Mai
(No air filter)

350 c.c. O.H.V. 376/5 220 30 376/3½ 3
500 c.c. O.H.V. 389/1 260 30 389/3½ 3

* Where an air filter is fitted, the needle position should be No. 2. not No. 3. Th e ty pe numb ers o f th e 195 4
350 c.c. and 500 c.c. Amal carburettors are 76AV/1ED and 89N/1ED respectively.

Jet jet Valve Position

Pilot Throttle Needle

To vary the strength of the running mixture (rarely necessary), it is necessary to

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adjust the height of the needle in the throttle valve, or else to fit a larger or smaller
size main-jet. The condition of the sparking plug provides an excellent guide to the
condition of the mixture (see page 73).

To Make a Slow-Running Adjustment. This should be effected with the engine
already warmed up. If the adjustment is appreciably at fault, screw home the pilot­air adjusting screw fully and then unscrew it (usually about two complete turns)
until the engine idles at an excessive speed, with the throttle twist-grip closed and
the throttle slide abutting the throttle-stop screw. The air lever should be fully open
and the ignition lever (where automatic ignition-advance is not provided) should be
set to obtain the best slow-running (half to two-thirds advanced).
Loosen the nut (omitted on the "Monobloc" carburettor) securing the throttle-stop
screw, and unscrew the latter until the engine slows up and begins to falter. Then
screw the pilot-air adjusting screw in or out as required to enable the engine to run
regularly and faster. To weaken the mixture, screw the pilot-air adjusting screw
outwards.
Slowly lower the throttle-stop screw until the engine again begins to falter. Then
lock the throttle-stop screw (standard carburettor) with the lock-nut and reset the
pilot-air adjusting screw to obtain the best slowrunning. If after making this second
adjustment the engine ticks over too fast, repeat the adjustment a third time.
The combined adjustment sounds complicated but in practice is quite simple. It is
important to avoid excessive richness of the slow-running mixture, especially if
much riding is done on small throttle openings; if the mixture is too rich,
considerable running on the pilot jet will occur while riding, with consequently a
high fuel consumption.
Aim at obtaining the best tick-over, preferably on a mixture just bordering on the
weak side. The engine should be on the point of spittingback.* When perfect slow­running has been obtained, tighten the locknut (standard carburettor) on the throttle­stop screw without disturbing the position of the screw.

Obstructed Pilot Jet. If the adjustment of the pilot jet does not obtain the desired
results and the engine will not idle nicely with the throttle almost closed, the air
lever fully open, and the ignition lever (where fitted) half to two-thirds advanced, it
is possible that the pilot jet is obstructed. The jet passage (on the standard
carburettor a duct drilled in the jet block) is very small and can readily become
choked.

* Rev the engine up and down sharply several times (whi le at rest and while riding) and note whether the
exhaust is nice and crisp, with no "flat spots" as the twist-grip is turned. It is essential to combine good tick­over with good acceleration.

To gain access to the pilot jet on the standard carburettor (see Fig. 8), remove the

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jet plug (Q) and the float chamber (R), and then detach the jet block (F) by pushing
or tapping it out of the mixing chamber. The pilot jet (J) can then be cleared by
blowing through it, or by means of a very fine strand of wire.
With the "Monobloc" carburettor (see Fig. 10) to remove the pilot jet (1 7),
remove the pilot jet cover-nut and then unscrew the jet itself which should be
thoroughly cleaned in petrol and then blown through. See that the air passage (6) to
the pilot jet, and also the pilot outlet, are quite clear.

Bad Slow-running. If it is found impossible to obtain good slow-running by

making the pilot-air adjustment as described
on page 17, it is probable that some defect
Pd, other than carburation is responsible for
preventing the engine running smoothly at
low revolutions. Air leaks or badly seating
valves may weaken the mixtur e. Defe cts in
the ignition system may also be responsible
for poor tick-over.
The sparking plug may be oily, or the
points set too close (see page 73).
Possibly the spark is excessively advanced
or the contact-breaker needs attention (see
page 77). Examine the slip ring for oil and
see that the pick-up brush is bedding down

FIG. 11. IF PERSISTENT "FLOODING"
OCCURS, LOOK FOR THESE DEFECTS
(standard type carburettor.)

Excessive Fuel Consumption. If in spite of careful checking on the tuning of the

carburettor, high fuel consumption continues, it is likely that one or more of the
under-mentioned causes is responsible for wastage of precious fuel. Late ignition
timing will eat into your petrol supplies quickly. The same applies to poor engine
compression due to badlyfitting piston rings or valves. Also take into consideration
the question of flooding due to a faulty float, air leakage at the joint between the
carburettor and the engine, weak valve springs. See that no wastage is caused by
slack petrol pipe union-nuts.

and in good condition. Also examine the h.t.
cable for signs ofshorting.

Twist-grip Adjustment. Adjustment should be such that the grip is free and easy
to twist, but "stays put." The spring tension on the twist-grip rotating sleeve is
regulated by a screw incorporated in one-half of the twistgrip body. To increase the
tension, loosen the lock-nut and turn the screw into the body as required.

It is possible to move the complete twist-grip on the. handlebars by slackening the

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two screws which clamp it in position. The best position of the twist-grip is that
which gives the cleanest and straightest path to the throttle cable between the
handlebars and the under-side of the petrol tank.

On 1945-53 models the throttle cable is initially coated with graphite lubricant

which suffices for an indefinite period, but when a new cable is fitted it should be
similarly greased. On 1954 and later models a nipple is provided for lubricating the
throttle cable, and so ensure smooth throttle operation. If any stiffness or jerkiness
occurs, inject a little engine, oil through the nipple. When doing this, apply the gun
as nearly vertically as possible, with the nozzle downwards.

CARBURETTOR MAINTENANCE

To ensure correct carburation it is advisable occasionally to remove the carburettor

from the engine, strip it down completely, and then thoroughly clean it. It is a good
plan to do this about every six months as described below.

Dismantling Standard Carburettor. First close both petrol taps and disconnect
the twin petrol pipes from the carburettor by undoing the single union-nut at the
base of the float chamber. Referring to Fig. 8, loosen the jet plug (Q) and slacken
the mixing chamber union-nut (E).
Unscrew the mixing-chamber knurled cap-ring (Z) held by the retaining spring
(ZI) at the top of the carburettor, and remove the two nuts securing the carburettor
flange to the face of the inlet port. Now remove the body of the carburettor,
complete with the float chamber, from the engine.
When removing the carburettor, pull the air valve (D) and the throttle valve (B),
together with the jet needle (C), from the mixing chamber (A); temporarily tie up the
slides out of the way. It is not necessary to remove the air and throttle slides from
the control cables unless it is desired to renew the slides or control cables.
The jet needle (C) can be adjusted for position in, or removed from, the throttle
slide by removing the spring clip from the top of the slide. Examine the carburettor­flange washer, and, if damaged, renew it.
With the carburettor removed from the engine, proceed to remove the jet plug (Q)
and the float chamber (R). Also remove the main jet (P) and the needle jet (0).
Then completely unscrew the mixing-chamber unionnut (E) and push the jet block
(F) right out; if stiff, tap the jet block out gently with a wooden stump. Unscrew the
float-chamber cover (W) after loosening the locking screw (X). Then withdraw the
float by pinching the clip (V) inwards, and pull gently upwards.

Dismantling "Monobloc" Carburettor. Close both petrol taps and disconnect

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the twin petrol pipes by undoing the banjo bolt (8) over the float chamber (see Fig.

10). Referring to Fig. 10, unscrew the mixingchamber knurled cap-ring (2) on top of
the carburettor and remove the two nuts securing the carburettor flange to the face of
the inlet port. Then remove the body of the carburettor (21), complete with the
integral float chamber (13). While removing the carburettor, pull the air valve (3)
and the throttle valve (24) from the mixing chamber and tie them up temporarily out
of the way. As mentioned in the instructions for the standard type carburettor, it is
rarely necessary to disconnect the slides from the cables. Check that the flange
washer is sound.
Further dismantling is straightforward. Referring to Fig. 10, to remove the jet
needle (23), withdraw the jet-needle clip (4) on top of the throttle valve, and remove
the needle. To obtain access to the float (10), remove the three screws (11) securing
the float-chamber cover (12). Lift out the hinged float (10) and withdraw the
moulded-nylon needle (9). Lay both aside for cleaning. The float-chamber vent, by
the way, is embodied in the tickler assembly (7), and the top-feed union houses a
filter element of fine gauze which is rapidly accessible for cleaning.
To remove the main jet (14), remove the main-jet cover and unscrew the jet from the
jet holder (15), which should also be unscrewed. Remove the jet-block locating screw
(1 9) to the left of and slightly below the pilot air adjusting screw.
Then push or tap out the jet block (5) and fibre seal (22) through the large end of the
mixing chamber (21). To remove the pilot jet (17), remove the pilot-jet cover nut
and unscrew the jet.

To Clean the Carburettor. Wash all the carburettor components, thoroughly
clean with petrol and blow through the various ducts and passages to make sure they
are quite clear. Avoid using a fluffy rag for drying purposes. Pay special attention to
the small pilot-jet passages in the jet block on both the standard and "Monobloc"
type instruments. See that all impurities are removed from inside the float chamber.
On the "Monobloc" carburettor do not forget to clean the detachable pilot jet and the
filter gauze inside the top-feed union for the float chamber.

Inspecting the Parts. When dismantling the carburettor it is advisable to make a
close inspection of the various parts if the carburettor has been in continuous service
for a considerable period.

1. THE FLOAT CHAMBER. Examine the components very carefully and
check that the vent is unobstructed. The float must be in perfect condition. Clean
the moulded-nylon needle on the "Monobloc" carburettor very thoroughly, and be
careful not to damage it. On a standard carburettor hand-polish the valve part of the
float needle by rotating the needle on its seat while pulling it vertically upwards. If a
istinct shoulder is visible on the needle where it seats, renew the needle at once.
Check for any sign of bending or distortion of the clip.

2. THE THROTTLE VALVE. Test this for fit in the mixing chamber. Should

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excessive play exist, renew the slide forthwith. See that the new slide has the correct
amount of cut-away-

3. THE JET-NEEDLE CLIP. The spring clip securing the tapere d needle to
the throttle valve must grip the needle firmly, and free rotation must not occur, as
this causes the needle groove to wear. Always be careful to replace the needle with
the clip in the correct groove, (see page 16).

4. THE JET BLOCK. Before tapping this home in the mixing chamber verify
by blowing that the pilot-jet ducts are clear and that the jet-block fibre seal is in
good condition.

5. THE CARBURETTOR FLANGE. Examine this for truth with a straight
edge. Distortion sometimes occurs, and this may cause an air leak. If the flange is
slightly concave, file and rub down the face with emery cloth until it is dead flat and
smooth.

Assembling Standard Carburettor. Referring to Fig. 8, refit the jet block (F)
with the fibre washer on its under-side, and screw on lightly the mixingchamber
union nut (E). Screw in the needle jet (0) and the main jet (P). Open the air lever
7/8 in. and the throttle twist-grip half way; grasp the air slide between the thumb and
the finger and make sure that the jet needle enters the central hole in the barrel (H).
Slightly turn the throttle slide until it enters the barrel guide when, on pushing down
the slides, the air valve should enter its guide. If not, slightly move the mixing­chamber cap (Y), when the air valve will slide into position. Screw home the
mixingchamber knurled cap-ring (Z). No force is necessary.
Replace the carburettor-flange washer, offer up the carburettor body and secure in
position by tightening the two nuts evenly. Replace the float and needle in the float
chamber, holding the needle against its seating with a pencil until the float (T) and
needle clip (V) are slipped into position. See that the spring clip enters the needle
groove. Then screw home the float-chamber cover securely and lock in position by
tightening the lockscrew (X).
Insert the jet plug (Q) in the union nut (E) and very firmly tighten the union nut with
a suitable spanner. Remove the jet plug, fit the float chamber, and secure with the.
jet plug. Be sure there is a fibre washer above and below the float-chamber lug as
shown in Fig. 8. When the float chamber has been correctly positioned, tighten the
jet plug firmly. Finally reconnect the twin petrol pipes and tighten the union nut at
the base of the float chamber. In the event of the pilot-jet adjustment having been
disturbed, re-tune as described on page 17.

Wear of Jet Needle. The needle itself does not wear, though some wear of the

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groove may occur if the jet-needle clip is not grasping the needle firmly. If the
mixture is too rich with the clip in No. 1 groove (nearest the top), it is probable that
the needle jet needs to be renewed because of wear. It is assumed that the carburettor
is correctly tuned and that no flooding occurs (see page 18).

Assembling "Monobloc" Carburettor. Do this in the reverse order of
dismantling. Referring to Fig. 10, screw home the pilot jet (17) and the pilot jet
cover-nut, not omitting to replace its washer. Push or tap home the jet block (5) and
fibre seal (22) through the large end of the mixing chamber (21). Check that the
fibre-seal fitted to the stub of the jet block is in good condition. Then fit the jet­block locating-screw (19). Screw the main-jet holder (15) into the jet block, after
checking that the washer for the holder is sound. Next screw the main jet (1 6) into
the jet holder.
Replace the moulded-nylon needle (9) in the float chamber (13), and fit the hinged
float (10) with the narrow side of the hinge uppermost. Afterwards fit the float­chamber cover (12) and secure by means of the three screws (11). Verify that the
cover and body faces are undamaged and quite clean. Renew the washer.
If previously removed, attach the jet needle (23) to the throttle valve (24) and secure
with the jet-needle clip (4), making sure that the clip enters the correct groove. (See
page 16.)
Position the carburettor-flange washer, and offer up the carburettor to the face of the
inlet port after easing the air and throttle valves (3) and (24) down into the mixing
chamber (see hints on page 21 concerning the standard carburettor). When easing
the throttle valve home, make sure that the tapered ' jet-needle (23) really enters the
hole in the jet block (5). Secure the carburettor flange firmly to the engine by means
of the two nuts, and tighten these evenly. Tighten down firmly the mixing-chamber
knurled cap-ring (2) and see that the throttle slide works freely when this is
tightened down.
Finally reconnect the twin petrol pipes by tightening the banjo bolt (8) over the float
chamber (13).

THE AIR FILTER

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Maintenance. An air filter of the"oil-wetted" type is fitted as an optional extra to
A.J.S. models. In the United Kingdom the roads are excellent and the air
comparatively free from dust, and it is questionable whether the fitting of an air
filter, except for use abroad in countries where the roads are poor and dusty, will
appreciably prolong the life of the cylinder and piston.
Where an air filter is fitted, it is advisable about every 1,000 miles to withdraw the
filter element; wash it thoroughly in petrol, paraffin, or other suitable solvent, and
allow to dry. Then submerge the element completely for a few minutes in thin oil
(SAE 20) of the type recommended on page 65 for the "Teledraulic" front forks.
Remove the element, allow all surplus oil to drain off, and afterwards replace in the
air-filter case. It is desirable to renew the filter element about every 10,000 miles.

To Remove Filter Element (1956-7 Models). First pull the rubber hose off the air­intake of the "Monobloc" carburettor after releasing the clip (1957). Next remove
the frame cover and pull off the hose end from the air filter. Then remove the bolts
which secure the air filter to the oil tank and remove the complete filter assembly.
Note that the filter element is secured in its cage by bolts, nuts, and locking
washers.
After cleaning the filter (see a previous paragraph) replace it. When replacing the
hose on the filter, see that it is properly located. The end of the rubber hose is split
along the edge of the lip, and it is important to make sure that the neck of the filter
assembly enters this groove.23

CHAPTER III

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THE LIGHTING SYSTEM

To ensure maximum illumination from the lamps at all times, a little attention to the
equipment is normally necessary and in practice is generally confined to: keeping
the lamps clean; renewing dud bulbs; toppingup the battery regularly; taking
occasional specific-gravity readings; periodically inspecting the dynamo brushes and
commutator (particularly important on 1945-51 models where dynamo removal is
rather complicated); the keeping of all connexions clean and tight; and the
prevention or repair of frayed leads by taping where necessary.

ILLUMINATION

The Switch Positions. The lighting switch (see Figs. 2 and 3) situated on top of

1945-57 headlamps causes the dynamo to charge in all three switch positions, which
are as follows-

"OFF" - No lights on.
"L" - Headlamp pilot, rear, and speedometer bulbs on.
"H" - Headlamp main, rear, and speedometer bulbs on.

Headlamp Alignment. Incorrect headlamp alignment and/or an outof-focus main
bulb give reduced road illumination and liability to dazzle other road users. Both
faults are simply rectified.
To check the headlamp alignment, take your A.J.S. to a straight, level stretch of
road, turn the lighting switch to the "H" position, and operate the dipping switch so
that the main driving light is switched on. The beam of light should, if alignment is
correct, be straight ahead and slightly below the horizontal. If the headlamp is
mounted so that the beam of light is elevated or projects too much on the road,
slacken the mounting bolts or nuts whicl;sec-ure the headlamp to its brackets and
then tilt the headlamp slightly down or up until correct alignment is obtained.
Afterwards secure the headlamp firmly.

Headlamp Focusing. On 1945-50 A.J.S. machines the double-filament main bulb
(movable) is focused to give the best illumination. Provided genuine Lucas bulbs of
the correct wattage and number are fitted as replacements, subsequent refocusing
should be unnecessary. Where a Lucas bulb is not available, or the focusing
adjustment has been disturbed, it is necessary to re-focus. At the same time it is
desirable to check the headlamp alignment as previously described.

The headlamp is correctly focused when the reflected rays of light are almost

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parallel and when the beam, projected upon a wall (30-40 ft from the machine)
illuminates brightly a circular area of minimum diameter. The filament for the main
driving light should be as near as possible to the focal point of the reflector in order to
obtain a parallel beam. If the filament is positioned in front of the focal point, a
converging beam (with dark centre portion) results. If, on the other hand, the
filament is positioned behind the focal point, a diverging beam is obtained.
Both converging and diverging beams are highly undesirable as they illuminate the
road poorly and are liable to dazzle other road users. Adjust the focus of the
headlamp immediately if its beam is not uniform, is of short range, and has a dark
centre. To focus the headlamp it is obviously necessary to move the main bulb
backwards or forwards on the reflector axis according to whether the beam is
converging or diverging respectively.

THE LAMPS (1945-8 MODELS)

To Focus DU-42 Headlamp (1945-48). You should take your machine to a level

stretch of road and focus the headlamp against a wall some distance (say 30-40 ft)
from the machine. The lamp front and reflector must first be removed. To do this,
release the front fixing-clip (see Fig. 12) which secures the base of the lamp front
and pull the latter outwards. As the lamp front and reflector come away together,
free the top tag of the lamp front from the body of the lamp by lifting the lamp front
slightly upwards.
The double-filament main bulb holder is adjustable in the plate fitted to the back of
the reflector, and as may be seen in Fig. 12 there is a clamping clip for focusing
adjustment. To focus the bulb, loosen the clamping screw on the clip and push the
bulb-holder in or out of the clamping clip as required. Several focusing adjustments
may be needed. After making each adjustment, replace the lamp front and reflector
and test the beam for focus (see earlier paragraph). When the correct focus is
obtained, tighten the screw on the bulb-holder clamping clip firmly.
When fitting the lamp front and reflector, first locate the top tag in the slot of the
lamp body and then press home the lamp front towards the body. Finally, fasten the
lamp front by means of the spring fixing-clip at the base of the lamp.

Lamp Bulb Renewal (1945-8). If a bulb "goes west," fit a bulb of the correct type.
Most large garages and accessory dealers stock genuine Lucas bulbs, which are all
specially tested to check that the filament is correctly positioned to give maximum
results with Lucas reflectors.
It is advisable not to wait till bulbs actually burn out but to renew them after long
service. This avoids the risk of incorrect focusing caused by filaments sagging,
which sometimes occurs after extensive use.

Lucas bulbs have their metal caps marked with a number for identification purposes

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and it is important when renewing a bulb to see that it has the correct number on its
cap. The correct headlamp double-filament main bulb is No. 168; and that of the
headlamp pilot-bulb and sidecar lamp bulb, 200. The number 168 bulb is 6 V., 24
W., S.B.C. The number 200 bulb is 6 V., 3 W., S.B.C. Fit a No. 205 (6 V., 6 W.)
rear-lamp bulb.

FIG. 12. LUCAS DU-42 HEADLAMP (1945-8 MODELS)
The lamp front and reflector are shown detached from the lamp body to reveal the clamping clip, which must
be loosened to enable the bulb-holder to be moved for focusing.

The headlamp main and pilot bulbs are fitted in holders attached to the plate secured
to the rear of the reflector by two spring wires. To remove the plate, complete with
the two holders and bulbs, it is only necessary to spring the two wires outwards until
they are clear of the plate.
To remove the headlamp main bulb or pilot bulb from its holder, it is only necessary
to release the bayonet fixing and withdraw the bulb.
It is essential when fitting a new main bulb to see that it is the correct way round, i.e.
with the dipped beam filament above the centre filament. The word "Top" is etched
on Lucas main bulbs to indicate the correct position in the bulb holder. After fitting
a new main bulb it is advisable to check the focus of the headlamp (see page 24).

Removing Reflector (1945-8). Remove the four spring clips that secure the

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reflector and glass to the headlamp front and detach the reflector, the cork packing
strip between the reflector and glass, and the glass itself.
To assemble the reflector and glass, the following procedure is necessary. First
position the glass in the lamp front. Next, at the cork packing strip to the reflector
edge by pressing it into the pins which are integral with the lamp front. Then place
the reflector assembly (complete with bulb holders) on top of the glass. Make sure
that the top of the reflector registers with the top of the lamp front. Finally, replace
the four spring clips so that they are about equally spaced.

The WT203 Rear Lamp (1945-8).

The lamp body, with bulb holder, is
secured to the rear number plate by
means of three bolts with appropriate
washers and nuts. To detach the portion
of the rear lamp housing the red glass,
give it a half-turn to the left and then pull
it outwards, as shown in Fig. 13 . When
replaci ng the out er portion of the lamp,
engage the slots i n the body of the lamp
with the two spring- clips on the body of
the lamp and push right home to effect
full engagement.

Cleaning Lucas Lamps. Clean ebony black surfaces with a good type of car
polish. Chromium-plated surfaces do not tarnish and should be wiped over with a
damp cloth occasionally to remove dirt or dust. Care must be taken when handling a
reflector not to scratch it accidentally, and on no account must metal polish be used
to clean it.
A fine, colourless and transparent covering is provided on the Lucas reflectors for
protection purposes, and this covering can readily be cleaned without any risk of
damaging the actual surface of the reflector. Polish the reflector covering lightly
with a clean, dry, soft cloth or a chamois leather. No other treatment is desirable.

FIG. 13. LUCAS REAR LAMP
(TYPE WT203)

The lamp shown is fitted to some 1945-!
models, but later machines have the
MT211 or 46711 type (page 33)

Ammeter Readings. This centre-zero instrument shows a charge on one side and a
discharge on the other and is provided to give a reading of the amount of current
flowing to or from the battery. For instance, if the dynamo output is 3 amp. at a
certain speed, and the pilot bulb and rear lamp are on, thereby absorbing, say, 1 amp.,
then 2 amp. remain for battery charging, and the ammeter will therefore indicate 2
amp. At very low r.p.m. the ammeter reading is zero because the dynamo armature
is not rotating fast enough to generate sufficient current to give a battery charge. (See
also page 40).

Ammeter Removal. Should it be necessary for some reason to remove the am-

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meter on a Model 16M or 18, this can readily be effected. Referring to Figs. 14
and 19, detach the panel from the top of the Lucas headlamp by unscrewing the
three retaining screws. Then unscrew the two ammeter terminal screws shown at
A and disconnect the wires. Next bend back the four metal tags shown at B. When
these have been dealt with, ammeter C can be removed bodily from the panel.
Replace the ammeter, in the reverse order of removal. Do not touch switch D.

THE LA MPS (1949 ONWARDS)

The headlamp and rear lamps fitted 1949 onwards
are different from previous types and the following
notes should be studied by owners of 1949 and
subsequent models.

Focusing SSU700P Headlamp (1949-50).

Focusing should always be effected on a level
stretch of road with the headlamp beam directed
against a wall some 30-40 ft distant from the
machine. Note the general remarks on page 24
concerning focusing, and see that the headlamp is
aligned correctly. On the SSU700P headlamps, the
lamp front and the light-unit assembly (reflector and
glass) are removed together. To remove the lamp

FIG. 14. AMMETER AND
SWITCH PANEL

lower tag from the shell of the headlamp. The double-filament main bulb is
adjustable in its holder and has a clamp tightened by one screw. To focus the
main bulb, loosen this screw and push the bulb holder inwards or outwards until
the correct focus is obtained. Afterwards firmly retighten the screw which clamps
the bulb holder. Next engage the lower tag on the lamp rim with the small slit in
the lamp shell and carefully press the top of the rim back into the lamp shell.
Finally retighten the screw on the top of the lamp body.

front, loosen the screw on top of the headlamp
body, withdraw the rim outward from the top, and as
the lamp front emerges raise it a little to free the

The "Pre-Focus" 1951 SSU700P Headlamp. On the 1951 models the Lucas

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SSU700P headlamp has a "pre-focus" main bulb, and no focusing adjustment is
provided. Details of the bulb holder assembly are shown in Fig. 18. The "pre-focus"
bulb filament is in permanent focus relatively to the reflector, and the pilot bulb
mounted at the rear of the back shell provides illumination through a transparent
window in the reflector.
To obtain access to the main and pilot bulbs, remove the lamp front, with light- unit
assembly (see Fig. 16) as previously described for the SSU700P headlamp fitted to
1949-50 models.

The 1952-3 SSU700P/1 Headlamp. This headlamp (see Fig. 16) is identical to the
1951 SSU700P "pre-focus" type headlamp just described except that instead of the
pilot bulb being mounted above the "pre-focus" main bulb as shown in Fig. 16, it is
mounted in an inverted position in a detachable carrier-plate at the base of the lamp
and shines through an underslung pilot lens, not perhaps an ideal arrangement.
If desired, suitable pilot lamps can be substituted (see Fig. 17) for the underslung
pilot light. Access to the "pre-focus" main bulb and the pilot bulb is obtained by
removing the lamp front (with light-unit assembly) as already described for the
1949-50 SSU700P headlamp.

The 1954-7 Headlamps. These Lucas headlamps are basically similar to the 1952-3
SSU700P/1 "pre-focus" type headlamp, but the pilot-light arrangement is quite
different. As may be seen in Fig. 17, two smart torpedo-shaped pilot lamps are
secured to the front-fork lamp supports by tubular bolts, through each of which a
lead passes to the adjacent pilot lamp. On 1954 headlamps the ammeter and lighting
switch are mounted, one behind the other, on a panel on top of the headlamp, but on
1955-7 headlamps the arrangement is as shown in Fig. 17.
On all 1954-7 headlamps, to obtain access to the double filament "pre-focus" main
bulb, remove the lamp front (with light-unit assembly) as described on page 28 for
the 1949-50 SSU700P headlamp. To get at the bulb in each streamlined pilot bulb,
remove the screw at the rear and gently pull forward on the glass rim.

Separating Light Unit from Rim. On all Lucas 1949-50 type headlamps, and
1951 and later models, the front glass and reflector are made as one assembly (the
"light-unit") and cannot be separated. The light-unit, however, can be removed from
the chromium-plated rim by disengaging the spring clips from the turned-up inner
edge of the rim by pressing with the blade of a screwdriver, working away from the
edge.

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FIG. 15. LUCAS SSU700P HEADLAMP WITH FRONT AND REFLECTOR REMOVED (1949-50
MODELS)
On 1951 A.J.S. machines with 5SU700P headlamp the lamp glass and reflector are not detachable from each
other; the two components comprise the "light unit" assembly, secured to the rim by spring clips. A back shell
houses the pilot bulb and a pre-focus" main bulb.

FIG. 16. LUCAS SSU700P/1 "PRE-FOCUS" HEADLAMP WITH FRONT (LIGHT-UNIT ASSEMBLY
INCLUDED) AND MAIN BULB WITHDRAWN (1952-3 MODELS)
Note the remarks below Fig. 15 concerning the light-un it.

To fit the light-unit assembly to the rim, lay the unit in the rim so that the location

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block on the unit engages the forked bracket on the rim, and then spring home the
spring clips. See that they are spaced at equal distances around the rim.

FIG. 17. LUCAS "PRE-FOCUS" HEADLAMP HOUSING AMMETER, LIGHTING SWITCH, AND
SPEEDOMETER (1955 ONWARDS)
Streamlined twin pilot-lamps were introduced in 1954 and are made to A.M.C. specification

Headlamp Bulb Renewal. Fit genuine Lucas bulbs if occasion arises to renew
them, and do not defer renewal until actual bulb failure occurs (see page 25). To
remove the cap (non-"pre-focus" headlamp) which carries the bulbs, depress one of
the two spring plungers which secure the cap to the reflector and tilt the cap bodily.
When replacing the bulb holder, engage the holder carrier-cap in the position at
which the pilot bulb is against the small window in the reflector.
When fitting a non-"pre-focus" main bulb, see that it is fitted with the dipped beam
filament above the centre filament. Lucas main bulbs have the word "TOP" etched
to indicate the correct position, in the bulb holder. Check the main bulb for focus
after renewing it.
When fitting a "pre-focus" bulb (see Fig. 18) turn the back shell anticlockwise and
withdraw it. You can then remove the bulb from the back of the reflector. Insert the
correct Lucas-type bulb replacement in the bulb holder with its locating flange
positioned, engage the projections on the inside of the back shell with the slots in the
bulb holder, press on, and secure by turning clockwise.

Correct Bulb Renewals. The 1949-50 Lucas type SSU700P headlamp (with

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focusing adjustment) takes a 6-volt, 24/24-watt No. 168 S.B.C. double-filament main
bulb (bayonet-fixing type), and a 6-volt,
3-watt No. 988 M.C.C. pilot bulb.
The 1951-7 headlamps ("pre-focus"
type) require a No. 312 (30/24-watt)
Lucas double-filament main bulb which
has a broad locating flange on the cap.
Note that a No. 312 bulb cannot be used
in a focusing" type lamp, nor can a No.
168 bulb be used in a "pre-focus" type

FIG. 18. LUCAS LIGHT-UNIT ASSEMBLY FIG. 19. AMMETER AND SWITCH PANEL
AND BACK SHELL WITH "PRE-FOCUS" REMOVED (1951-4)
MAIN BULB AND PILOT BULB (1951 The cable harness (see Fig. 14) is not shown.
MODELS) For location of numbered parts,

headlamp incorporating a Lucas light-unit assembly. All 1951-7 headlamps require a
No. 988 pilot bulb. This is not suitable for 1949-52 rear lamps. 1953 and later
Lucas stop-tail lamps require a 6-volt, 18/6-watt, No. 384 double-filament bulb.
The correct speedometer bulb is a 6-volt, 1.8-watt No. 53205 M.C.C.

see wiring diagram (Fig. 29)

The Ammeter. The sketches numbered Figs. 14 and 19 show the back of the panel
housing the ammeter and lighting switch on 1949-50 and 1951-4 models respectively,
1955-7 models have the ammeter and lighting switch built into the Lucas headlamp
as shown in Fig. 17. Note the remarks on pages 27 and 40 concerning ammeter
readings. Do not meddle with the ammeter. If its needle sticks or "flutters," take the
motor-cycle to the nearest Lucas service depot.

Cleaning Lucas Lamps. Observe the instructio ns given on page 27, but note that

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on 1949 and later "sealed beam" Lucas headlamps (with Lucas light-unit) the
reflector cannot be detached for cleaning.

The M1211 Rear Lamp. This rear lamp, of Lucas design, is secured to the rear
number plate of some 1948-9 models by means of a three-bolt fixing. To remove the
cover carrying the red glass, push in and turn in an anti-clockwise direction. To
replace the cover of the lamp, locate the slots in the front portion over the retaining
pegs in the lamp body, push inwards, and turn in an anti-clockwise direction.

FIG. 20. THE LUCAS STOP-TAIL LAMP
This lamp has a double-filament bulb.

The 467/1 Rear Lamp. The Lucas rear-lamp body, complete with bulb holder, is
secured on 1949 models to the rear number-plate by means of two nuts and spring
washers. To remove the cover securing the red glass, loosen the captive screw which
secures it, and withdraw the cover.

The 467/2 Rear Lamp. On 1950-52 A.J.S. models a Lucas type 467/2 rear lamp is
secured to the rear number-plate by two nuts and spring washers. A sleeve nut
secures the cover (carrying the red glass) to the body of the lamp. To fit a
replacement bulb, remove the sleeve nut and withdraw the cover and glass.

Stop-tail Lamps. 1953 and later A.J.S. machines have Lucas stop-tail lamps of the
type shown in Fig. 20. The lamp has a double-filament 6-volt, 18/6-watt bulb; the
6-watt filament serves as the normal rear light and the 18-watt filament is
illuminated only when the rear-brake pedal is depressed. To obtain access to the
bulb it is only necessary to remove two screws and withdraw the thermoplastic
cover. To prevent incorrect fitting of the No. 384 bulb, its securing pins are onset.

MAINTENANCE OF BATTERY (LEAD ACID)

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Neglect of the battery quickly brings trouble, and correct attention in regard to its
maintenance is vitally important. Upon it depend the lamps and horn.

Topping-up the Battery. Examine the acid level about every four weeks, and
even more frequently in tropical climates. Unscrew the battery clamping screw and
remove the battery after first disconnecting the battery positive and negative leads.
On 1956-7 models the Lucas battery is housed in a front compartment of the tool
box as shown in Fig. 23.

FIGS. 21 and 22. KEEP THE ELECTROLYTE LEVEL WITH THE TO PS OF THE PLAT E SEPARATO RS

Fig. 21 shows the Lucas type PUW-7E-4 battery fitted prior to 1954, and Fig. 22 the later PU7E/9 battery
with correct acid-level device.

To remove the battery on 1956 models, first release the rubber strap by grasping the
loop attached to its lower end; pull downwards until the strap and loop are freed from
the retaining clip at the platform base, and permit the rubber strap to slacken.
Then lift the battery out.
To remove the battery on 1957 models, grasp the rubber strap with the fingers
between the battery case and rubber strap. Push the strap downwards until it is
possible to free the metal toggle from the strap retaining-clip, then carefully take the
battery out. Take off the battery lid and remove the three vent plugs. Inspect the hole
in each vent plug and make certain that is is not obstructed. A choke d vent plug
hole wi ll result in an increase of pressure in the cell owing to gassing," and this may
cause trouble. Wipe the top of the battery clean with a rag and verify that the
washer (where fitted) beneath each vent plug, to prevent leakage, is in position.

After wiping the top of the battery, either destroy the rag or wash it thoroughly,

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using several changes of water. See that a supply of clean distilled water is to hand.
Topping-up is necessary because the distilled water, unlike the acid, is gradually lost
through evaporation.

FIG. 23. A 1956-7 REFINEMENT-NEAT ENCLOSURE OF THE BATTERY AND C.V.C. UNIT IN THE
TOOL BOX
The compensated-voltage-control unit is housed in a sponge-rubber holder. On 1957 models the tool-box lid is
quickly detachable instead of being hinged.

Be careful not to hold a naked light near the vents. If the level is below the tops of
the separators, add distilled water as required to bring the level correct (see Figs. 21
and 22). This should be done just before a charge run, as the agitation due to
running and the gassing will thoroughly mix the solution. Acid must not be added
to the electrolyte unless the solution has been spilled. If the solution has been
spilled by accident, add diluted sulphuric acid of specific gravity equal to that in the
cells.
Undoubtedly the best way to top-up a PUW-7E-4 type battery is to use a Lucas
battery filler. Insert its nozzle into each cell, with the nozzle resting

on the separators. Hold the battery filler in this position until air bubbles cease to

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rise in the glass container. The electrolyte level should then be correct, but examine
it to make sure.
On 1954 and later machines with the PU7E/9 battery, pour distilled water round the
flange (not the tube) of the acid-level device (see Fig. 22) until it ceases to drain into
the cell. Then lift the tube sli ghtly to enable the small amount of water in the

FIG. 24. LUCAS HYDROMETER BEING USED TO CHECK SPECIFIC GRAVITY OF BATTERY
ELECTROLYTE

flange to drain into the cell. The electrolyte level should then be correct. Inspect to
make certain. If the battery needs to be topped-up very often, it is possible that the
C.V.C. unit needs to be adjusted; if one cell requires more freque nt topping-up than
the others, probably the battery case, or container, is cracked, and battery renewal is
called for.

Checking Specific Gravity. Very occasionally, hydrometer readings (specific­gravity values) should be taken of the solution in each of the cells. The method of
doing this is shown in Fig. 24. The Lucas hydrometer contains a graduated float
which indicates the specific gravity of the battery cell from which a sample of
electrolyte is taken.
After a sample has been taken and checked, it must, of course, be returned to the cell.
The taking of S.G. readings with a hydrometer is the most efficient way of
ascertaining the state of charge of the battery.

The S.G. readings should be approximately the same for all three cells, Should the

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reading for one cell differ substantially from the readings for the others, probably
some acid has been spilled or has leaked from the cell concerned. There is also a
possibility of a short circuit between the battery plates. In the latter case it will be
necessary toreturn the battery to a Lucas service depot for attention.
Under no circumstances must the battery be permitted to remain in a discharged
condition for long, or serious deterioration will occur. After checking the S.G.
readings and topping-up the cells, wipe the top of the battery and remove any spilled
electrolyte or water; replace the three vent plugs and the battery lid. Then fit and
tighten the battery clamping-screw, or secure with the rubber strap (1956~7 models).

Battery Connexions. Always keep the battery connexions clean, free from
corrosion, and tight, otherwise the ammeter readings will not indicate the true state of
charge of the battery and proper battery charging may not occur.

Correct Readings. With Lucas batteries fitted to A.J.S. machines, the specific
gravity readings at an acid temperature of approximately 60'F. should be: 1.280-1­300, battery fully charged; about 1.210 battery about half discharged; below 1. 1 50
battery fully discharged. If the temperature exceeds 60'F., add 0.002 to the
hydrometer reading for each 5 degrees rise in temperature above 60'F. Similarly if
the temperature is below 60'F., deduct 0.002 for each 5 degrees decrease in
temperature.
Never leave the battery in a discharged state for any appreciable period. A low state
of charge often is caused through parking the machine for long periods with the
lighting switch in the "L" position, unaccompanied by much daylight running, the
remedy is, of course, to undertake more daylight running and to keep the switch in
the "Off position as much as possible until the battery regains its normal state of
charge. If overcharging occurs, have the setting of the compensated-voltage-control
unit checked.

MAINTENANCE OF DYNAMO

It is not necessary to take any special precautions when merely inspecting the
commutator, but on making adjustments to the wiring circuit, it is essential to take
steps to prevent accidental "shorting." Disconnect the lead from the lighting switch
at the battery positive terminal (negative terminal where the battery positive is
cartfied). Push back the rubber shield and then unscrew the cable connector (where
fitted). When doing this be sure that the cable does not make contact with any metal
part of the frame, otherwise a "fat" spark will indicate that the battery was well
charged! When re-connecting the lead, pull the rubber shield well over the
connector.

General Overhaul. It is a good plan every 10,000-15,000 miles to entrust the
dynamo to a Lucas service depot for dismantling, cleaning, servicing, and
lubrication. Lubrication is referred to on page 59.

The Commutator and Brushgear. The Lucas E3AR and the E3-N dynamos will

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run satisfactorily for thousands of miles without attention other than occasional
inspection of the commutator and brushgear. It is advisable about every 5,000­6,000 miles, to remove the metal cover-band from the dynamo and make a careful
inspection.

The Brushes. The brushes must make good electrical contact with the commutator.
They must be absolutely clean and able to move freely in their

box-type holders, on holding back the retaining

springs and gently pulling the leads and then
releasing them. There must also be perfect
contact between both the brushes and the copper
segments of the commutator; the brush faces in
contact with the segments should be uniformly
polished. Clean the brushes with a petrol­moistened cloth after removing them. To do this,
pull back each brush-retaining spring (see Fig. 25)
and remove the brush by pulling on its lead,

FIG. 25. COMMUTATOR END OF
THE LUCAS DYNAMO WITH
COVER BAND REMOVED

Examine the carbon brushes for wear and unevenness, and true then top up if
necessary. Generally it is best to renew the brushes before serious wear develops, as
this prevents sparking, which causes blackening of the commutator and an unsteady
charging current. Always replace brushes in their original positions.
If Lucas brushes become so badly worn that it is necessary to remove them, this can
easily be done as follows: Release the eyelet on the brush lead by unscrewing the
hexagonal nut or screw at the terminal; then, holding back the spring lever out of the
way, withdraw the brush from its holder. Renew with genuine Lucas brushes.
The brush springs should be inspected occasionally to see that they have sufficient
tension to keep the brushes firmly pressed against the commutator when the dynamo
is running. It is particularly necessary to keep this in mind when the brushes have
been in use a long time and are very much worn down.
It is unwise to insert brushes of a grade other than that supplied with the dynamo, or
to change the tension springs. The arrangement provided has been made only after
many years' experience and will be found to give the best results and the longest
life. It is really best when the brushes become so worn that they no longer bed
down on the commutator, or their flexible leads are exposed on their running faces,
to have new brushes fitted at a Lucas service depot, as this ensures the brushes being
properly "bedded."

being careful to see that the brush pressure spring

is clear of the brush holder.

The Commutator Surface. The surface of the commutator segments should be

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kept clean and free from oil or brush dust, etc. Should any grease or oil work its
way on to the commutator through over-lubrication, it will not only cause sparking,
but, in addition, carbon and copper dust will collect in the grooves between the
commutator segments.
The best way to clean the commutator is, without disconnecting any leads, to
remove from its box-holder one of the main brushes and, inserting a fine dry duster,
hold it, with a suitably-shaped piece of wood, against the commutator surface,
causing the armature to be rotated by the kickstarter.* If the commutator is very
dirty, first moisten the cloth with petrol. The segments should be dark bronze and
highly polished.

To Adjust Dynamo Chain. The tension of the dynamo chain which lies behind
the primary chain (see Fig. 78) should be checked occasionally, after removing the
oil-bath case inspection cap (see page 62). Chain whip with the chain in its tightest
position, mid-way between the sprockets, should be approximately 1/4 in.
To make an eccentric adjustment for chain tension, first slacken the strap bolt
clamping the dynamo in its housing. Then apply (1945-51) the spanner (Part No.

017254) to the flats cast on the dynamo end-plate, on the left-hand side of the
dynamo. Now rotate the dynamo anti-clockwise until chain tension is felt to be
correct on passing a finger through the inspection-cap opening. Be careful not to
confuse the primary chain with the dynamo chain which lies behind the former (see
Fig. 78). Afterwards retighten the strap bolt and again check the tension of the
dynamo chain. If found to be correct, replace the inspection cap on the oil-bath
chain case (see page 63).

Dynamo Removal. Removal of the dynamo on 1945-51 models is a little difficult,
but is greatly simplified on 1952 and later models where the magneto is in front of
the cylinder instead of over the dynamo. Full instructions for 1945 onwards are
given on page 143.

Compensated Voltage Control (C.V.C.). All A.J.S. motor-cycles incorporate
compensated voltage control. The C.V.C. unit consists of a cut-out and voltage­regulator unit in a box beneath the saddle, beside the battery carrier, or (1956-7) in
the tool box. It is connected between the dynamo and battery and sees to it that the
battery is automatically charged the right amount by varying the dynamo output
according to the state of charge of the battery and the load imposed on it.

* Slow rotation is assisted by removing the sparking plug.

Current is prevented from flowing back from the battery to the dynamo at low

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r.p.m. by means of the cut-out which opens. As soon as the r.p.m. rise high enough
to enable the dynamo to charge the battery, the cut-out closes and completes the
circuit.
In all three lighting-switch positions (see page 24) the dynamo gives a controlled
output and thus relieves you of responsibility in regard to charging. The regulator

begins to operate when the dynamo voltage reaches
about 7.3 volt. During daylight running with the
battery well charged and the switch in the "Off
position, the dynamo gives only a trickle charge, and
the ammeter reading is unlikely to exceed 1-2 amp.
There is no danger of overcharging.
The regulator provides for an increase of dynamo
output as soon as the lamps are switched on. The
effect of switchin g t he lamps on after a long run with
the battery voltage high is often to cause a temporary
discharge reading at the ammeter, but fairly soon the
voltage falls and the regulator responds, thereby
causing the output of the dynamo to balance the load
of the lamps. When the battery is in a discharged

FIG. 20. CONNECTIONS TO
COMPENSATED VOLTAGE­CONTROL UNIT

Do Not Tamper with C.V.C. Unit. The unit is sealed by the makers, as it should
not need adjustment once it is correctly set. If, however, the battery (in good
condition) is persistently under-charged or over-charged, suspect the C.V.C. unit
setting and have it checked, preferably at a Lucas service depot. Note that the
C.V.C. unit is retained by self-locking nuts, except on 1956-7 models where it is
retained in a sponge-rubber holder in a partition at the rear top corner of the tool box
(see Fig. 23). To remove the C.V.C. unit on a 1956-7 model, grasp it between the
fingers and thumb of one hand, and gently and firmly pull it away from the sponge­rubber holder.
As may be seen in Fig. 26, the four terminals of the C.V.C. unit are clearly marked
by the letters F.A.D.E. Leads from the F and D terminals are attached to similarly
marked terminals on the dynamo. The terminal marked A is connected to one of the
ammeter terminals, and the terminal marked E is earthed.

state, the regulator increases the dynamo output and
restores the battery to its normal state of charge in the
shortest possible time.

THE HORN

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Careful adjustment of the Lucas horn is made at the works, and subsequent
adjustment is rarely called for. Normally the horn should give long service without
any attention whatever. The vibrating parts do, however, gradually wear and, after
very considerable usage, some roughness and loss of tone may develop. This
necessitates an adjustment being made.

FIG. 27. ADJUSTMENT FOR TONE ON LUCAS HORN FITTED TO 1945-7 MODELS

Showing (left) the adjusting screw on 1945-50 models, and (right) the 1951 and later
adjustment.

To Make an Adjustment. Turn the adjusting screw shown in Fig. 27, with a
small screwdriver anti-clockwise until the horn just ceases to sound. Then release
the horn-push and turn the adjusting screw clockwise for six notches (one-quarter of
a turn) to restore the original horn performance. Should further adjustment be called
for, turn the adjusting screw clockwise one notch at a time. If results are un­successful, do not dismantle the horn but return it to a Lucas service depot.

If Horn Fails Completely or Partially. Do not immediately infer that the horn
has broken down or needs adjustment. Possible causes of the trouble are: a loose
fixing bolt; vibration of some adjacent part; a discharged battery; a loose connexion; a
short circuit in the wiring; or a defective push-switch. The last-mentioned may be
occasioned through poor electrical contact with the handlebars.

No Fuse. There is no fuse incorporated in the wiring circuit, which is purposely

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simplified, and capable of being understood by those with elementary electrical
knowledge. If care is taken to keep the various wires correctly connected, and to
maintain the connexions clean and firm, there is no risk of an excessive current
damaging any of the equipment or wiring.

Inspect the Wiring Occasionally. It is advisable occasionally to make a careful
inspection of the wiring, especially of the wires from the battery and the positive
lead from the dynamo to the lighting switch. See that the insulation is sound and not
chafed and that all connexions are clean and tight. Should the dynamo fail to
charge, this may be due to dynamo trouble, a faulty lead, or a faulty C.V.C. unit.
Tape up any loose or frayed leads.
As may be seen in Figs. 28-30, the ends of leads can be identified for connexion
purposes by means of their coloured sleeves. This greatly facilitates reconnecting the
wiring circuit in the event of the wires being disconnected from the various
terminals.
The leads connected to the terminals marked D and F on the dynamo and C.V.C. unit
must on no account be reversed. To prevent this being done, the screw in the
dynamo terminal-block is off-centre, and the screws securing the regulator
clamping-plate are of different size.

An Important Precaution. It is extremely important to disconnect one of the
battery leads (see page 37) if making any alterations to the wiring or removing the
lighting switch from the Lucas headlamp.

The Battery Lead Connexions. On all later ("King of the Road" type) Lucas
batteries detachable lead-connectors are privided at the battery terminals. To make a
lead connexion, unscrew the knurled terminal nut and withdraw the collet or cone­shaped insert. Note that the inserts for the two terminals are not interchangeable.
After baring the lead end for about an inch, thread the bared end through the knurled
nut and collet. Then insert the collet and cable into the terminal block after first
bending the wire strands over the narrow end of the collet. Tighten the knurled nut
firmly to secure the connexion.
On earlier type batteries other than those just referred to, detachable connectors are
not provided at the battery terminals. Instead, short lengths of cable are
permanently secured to the terminals, one for the earth connexion, and the other for
connecting to the lighting-switch cable by means of a screwed-type brass connector
(see Fig. 31). This is accessible on pushing back a protective rubber-sleeve. It is
vital that this sleeve is always kept pulled well over the connector.

(DOUBLE-FlLAMENT)

www.ajs-matchless.info

PILOT
BULB

SPEEDOMETER

LIGHT

DYNAMO

HEADLAMP
MAIN BULB

2

1

THE BOOK OF THE A.J.S.

REAR VIEW

OF

PANEL (HEADLAMP)

AMMETER

6

7

8

LIGHTING

SWITCH

1

2

8

4
4

4

DIPPER
SWITCH

4

7

REGULATOR (C.V.C. LIMIT)

CONTACTS
REGULATOR

RESISTANCE

HORN

6

5

CUT-OUT &

HORN
PUSH

5

SHUNT

CONTACTS

SERIES

D.

3

F

9

JUNCTION

TO SIDECAR LAMP

WHEN REQUIRED

SLEEVING COLOURS

–

RED

1

–

RED AND BLACK

2

–

YELLOW

3

–

BLUE

4

YELLOW AND PURPLE

–

5

YELLOW AND BLACK

–

6

–

BLUE AND WHITE

7

–

WHITE AMD PURPLE

8

–

GREEN AND BLACK

9

BLACK

–

10

FIG. 28. WIRING DIAGRAM OF LUCAS ELECTRICAL EQUIPMENT
FITTED TO ALL 1945-50 MODELS (NEGATIVE EARTH)

BOX

1

1

6

BATTERY

9

8 3

REAR

LAMP

10

1

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MA I N
BULB

SPEEDOMETER

LIGHT

HORN
PUSH

TO SPARKING

PLUG

BATTERY

(NEGATIVE

EARTH)

33

13

1

33

MAGNETO

BATTERY

CONNECTOR

PILOT
BULB

7

SNAP

CONNECTOR

13

14

14

AMMET E R

13

31

14
14

1

1

7

33

LIGH T I N G

8

28

28

23

8

33

SWITCH

RESISTANCE

SERIES

CONTACTS

SHUNT

REGULATOR

15 14

DYNAMO

REGULATOR FRAME

14

DIPPER
SWITCH

15

2331

1

TAIL LAMP

KEY TO COLOURED SLEEVES

1.

Red

7. Red and black

8. Yellow

13. Yellow and black

14. Blue

15. Blue and white

23. White and purple

28. Green and black

31. Purple

33. Black

FIG. 29. WIRING DIAGRAM FOR ALL 1951 MODELS (NEGATIVE EARTH)

44

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PILOT
LAMP

SPEEDOMETER

LIGHT

HORN
PUSH

MAGNETO

BATTERY

(POSITIVE

EARTH)

HORN

BLACK

BLACK

BROWN

MAIN LAMP

BLACK

BLACK

BROWN

BLACK

BLACK

AMMETER

PURPLE

LIGHTING

SWITCH

PURPLE

YELLOW

GREEN

BLACK

REGULATOR

SNAP

CONNECTOR

RESISTANCE

contacts

SHUNT

PILOT
LAMP

BLACK

BLUE
BLACK

DYNAMO

REGULATOR FRAME

DIPPER
SWITCH

TAIL
LAMP

FIG. 30. WIRING DIAGRAM FOR ALL 1954-7 MODELS

(POSITIVE EARTH)
This diagram applies also to all 1952-3 models (positive earth) but on these machines a single underslung
pilot-bulb (usedinstead of the twin pilot-lamps shown)has its lead connectedto No. 4 switchterminal. See
alsopage 42.

45

The Dynamo and C.V.C. Unit Connexions. The dynamo and C.V.C. unit

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connexions (see pages 40-1) are readily connected, but note the warning on page 42
concerning incorrect (reversed) connecting of the dynamo D and F terminals.To
make a connexion, slacken the fixing screw on the terminal block and withdraw the
clamping plate. Next remove the metal ferrule from each terminal. Pass about 1 in. of
the lead through the appropriate hole in the clamping plate and bare the end of the
lead for about 3/8 in. Replace the ferrule over the lead, bend back the wire strands
over the ferrule, and push the latter well home into its terminal. Afterwards screw
down the clamping plate firmly.

The Lighting Switch Connexions. These are inside the Lucas headlamp. Each
lead is secured to a metal terminal post by a grub-screw. To make a connexion, bare
the end of the lead for about 3/8 in., twist the wire strands together, and turn back
about 1/8 in. Remove the grub-screw from the appropriate terminal post, and then
push the wire through the slot in the side of the terminal post. Finally replace and
tighten the grub screw.

The Earth Leads. Connexions for the two earth leads (and the plug end of the h.t.

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cable) employ solid sleeve-type terminals, each with an eye at its extreme end.
The two (important) earth leads are one from the negative terminal (positive
terminal, 1952 onwards) of the battery, and the other from the compensated-voltage­control unit. The terminals of the earth leads are secured to the saddle-lug bolt
below the saddle or dualseat by a washer and screw (also a nut, 1955 onwards). See
that the earth connexions are kept clean and that their securing screw is kept firmly
tightened.
To make a connexion, first bare the end of the lead for about 3/8 in. Then slip the
sleeve-type terminal over the protruding wire and lead so that the bared end fully
enters the reduced core of the terminal. Now flatten that portion of the terminal
enclosing the lead, using a hammer or a vice.

Screwed-type Connectors (1945-54). To assist rear-wheel removal, a Lucas
screwed-type lead connector (see Fig. 31) is incorporated on 1945-8 models in the
lead to the Lucas rear lamp. It is located just above the rearwheel spindle and
comprises: a threaded sleeve, a collet, a gland nut, and a rubber sleeve. On 1950-4
models a similar type of connector is embodied in the lead connecting the battery
positive terminal (negative terminal, 1952 onwards) to the input side of the ammeter
in the headlamp.
To make a connexion, first bare the end of the leads for about 1/8 in. Then pass the
rubber sleeve (see Fig. 3 1) and the threaded sleeve over one lead, and slip the bared
end of this lead through the collet and bend back the wire strands. Next push the
bared end of the second lead through the gland nut and similarly bend back the wire
strands. Now screw the gland nut into the threaded sleeve and complete the
connexion by sliding the rubber sleeve right over the metal parts of the connector.
This will insulate the connector from the frame and help to prevent vibration
loosening the connexion.

Snap-type Connectors (1949 onwards). On all 1949 and subsequent models a
Lucas snap-type lead connector is incorporated in the lead connecting the C.V.C.
unit to the output side of the ammeter in the headlamp. Also on 1955-7 models the
leads (inside the headlamp) for the two pilot lamps have snap-type connectors. On
all 1949 and subsequent models to facilitate removal of the rear wheel, a similar type
of connector is embodied in the lead to the rear lamp.
The connector (see Fig. 32) comprises a metal connecting-sleeve, two nipples
soldered to the cable ends, and a rubber outer-sleeve to insulate the assembly and
help to keep it tight. The connecting sleeve is a split ferrule into which the soldered
cable nipples are a push-in snap fit. The method of making a connexion is self­obvious.

CHAPTER IV

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CORRECT LUBRICATION

The A.J.S. design dept. have done their best to ensure that correct lubrication
involves the minimum attention by the rider. This attention however is absolutely
vital and is dealt with in detail in this chapter. A summary of lubrication
requirements will be found on page 61.
Neglect to lubricate the engine and machine properly causes excessive friction and
head, accompanied by undue wear of the contacting bearing surfaces. Such neglect
can rapidly spoil a good motor-cycle and cause heavy repair bills, besides reducing
performance.

FIG. 33. THE "HEART" OF THE A.J.S. LUBRICATION SYSTEM
The oil pump is positioned on the engine a s shown in Fi g. 34. Above are shown the pump plunger, t he guide

screw, and the steel pin whic h fit s i nsi de t he h ollow gui de s cre w wit h t he relie ved end (sho wn d ark) a way from
the plunger. The plunger and the guide screw should not be disturbed during routine maintenance.

ENGINE LUBRICATION

The engine lubrication system on all A.J.S. O.H.V. models is of the full dry-sump
(D.S.) type, where all oil in the engine and oil tank is kept in constant circulation
while the engine is running. Its functioning is entirely automatic, but a little regular
attention is essential.

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FIG. 34. DIAGRAM SHOWING HOW THE OIL CIRCULATES INSIDE THE A.J.S. O.H.V. ENGINE

The above circulation diagram is applicable to all 1945 and later O.H.V. single cylinder engines. Oil is fed to
the overhead-rocker bushes besides being sprayed over the rocker s by jets . On 1954 and later engi nes an oil
lead is taken from the rocker bush to each rocker arm. 1956 and 1957 engines have no oil feed to the rear of
the cylinder.

The A.J.S. Oil Pump. The oil pump in the crankcase has a horizontal type steel

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plunger (Fig. 33) which combines rotary motion with reciprocating movement.
Rotary motion is imparted to the plunger by a worm onthe timing-side engine main­shaft. The reciprocating motion is obtained by thehardened pin in the hollow guide
screw (see Fig. 33) engaging the profiled cam-groove cut on the (larger) scavenge
end of the plunger.
The profiled cam-groove is designed so that the opening and closing of the two main
ports, and a small auxiliary port, are synchronized with the pumping impulses
obtained by plunger reciprocation. The scavenge (rear) end of the plunger (which is
totally enclosed in its housing by two end-caps) has a greater capacity than the
delivery end, and in consequence it keeps the crankcase sump in a "dry" state, all oil
being returned to the tank for further circulation.

How the Oil Circulates. Fig. 34 shows at a glance how the oil circulates i n the
A.J.S. engine with D.S. lubrication. The filtration of the oil in the tank (capacity: 3
pt., 1945-8; 4 pt., 1949-51 ; 4-lz pt., 1952-5; 5 pt., 1956; 4 pt., 1957) is shown
(1945-57 tanks) in Figs. 35 and 36.
The delivery (front) end of the plunger shown in Fig. 33 feeds oil under pressure to
the timing-side main bearing and connecting-rod big-end bearing through a passage
cut in the timing-side main shaft, flywheel, and crankpin. The piston and cylinder
bore are lubricated by surplus oil splashed from the big-end bearing.
Further provision for lubrication of the cylinder is included on 1945-55 engines.
The oil pump forces oil through a passage (equipped with ball-valve control) in the
crankcase to a circular channel in the cylinder base. The oil reaches the cylinder
bore through a number of small holes drilled in the channel. Surplus oil
automatically drains down into the sump of the crankcase.
The A.J.S. plunger pump also feeds a secondary oil supply to the timing gear and
rocker-box. The supply to the timing gear is fed through a passage in the timing­gear case. The oil collects in the timing-case until a predetermined level is reached.
As may be seen in Fig. 34, an external pipe connected to the front of the oil-pump
housing conveys the secondary oil-supply direct to the rocker-box and push-rod
ends.
The overhead inlet and exhaust-valve rockers inside the rocker-box are thoroughly
lubricated by means of jets above them. In addition, oil is fed to the rocker bushes
and (1 954 onwards) each rocker arm. The surplus oil drains to and lubricates both
valve guides. The oil supply to the guide for the inlet valve can be regulated by
means of a needle-pointed screw adjuster. This oil-supply adjustment is the only
one provided on the A.J.S. drysump lubrication system.
Surplus oil from the valve guides passes down the push-rod covers and the tappet
guides and enters the timing case. Here all engine oil, beyond that needed to keep
the level at the predetermined height, drains down into the sump of the crankcase.
The large-capacity scavenge end of the plunger pump sucks up the oil collected in
the sump from various parts of the engine and pumps it back via the upper pipe into
the oil tank for filtering and further circulation.

The whole of the oil in the tank and the engine is thus kept in constant

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circulation and the sump remains practically "dry." Up to 1952 an external engine­breather pipe was fitted, but from 1952 onwards the crankcase pressure-release
valve has been incorporated in the driving-side main shaft.

The Tank Filters. These keep the oil clean. A cut-away view of the A.J.S. oil
tank is shown in Figs. 35 and 36. As may be observed, a metal gauze filter is

FIG. 35. CUT-AWAY VIEW OF OIL TANK SHOWING THE FILTERS, ETC. (1952-5)
On 1945-51 tanks the smaller gauze-filter was integral with a screwed feed-pip e unio n (Fig. 37 ). and the
drain plug was at the rear. On 1956-7 models a pamier-typ e tank (Fig . 36 ) with a metal-g au ze filter is
provided. Prior to 1954 the rubber connexion fo r th e oil-return pipe w as o mitted .

KEY TO FIG. 35

1. Vent pipe (to prevent air locks). 6. Oil-return pipe.

2. Oil-return pipe orifice. 7. Oil-feed pipe.

3. Top-level mark. 8. Gauze filter.

4. Low-level mark. 9. Tube enclosing felt element.

5. Drain plug. 10. Cap on main filter.

incorporated in the delivery or feed-pipe union. It should be noted that the sole

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object of this filter is to trap any dirt, pieces of fluff, etc., which may get into the oil
tank while it is being replenished.
The main filter (1945-55 models) is a detachable fabric-type. It comprises a long
felt-element contained within an upright tubular wire-cage. As may be noticed in
Fig. 35, all the engine oil returned to the scavenge end of the pump has to percolate
through the felt element and wire cage which are supported by a cylindrical housing
inside the tank.

FIG. 36. CUT-AWAY VIEW OF OIL TANK ON 1956 MODELS
The above arrangement applies to 1957 models, excep t fo r the add ition of two ex tra holes at the top of the oil­return pipe, and the shrouding within the tank of the (externally located) vent pipe.

KEY TO FIG. 36

1. Oil-return pipe orifice. 5. Gauze filter (metal).

2. Top level mark. 6. Drain plug.

3. Oil-return pipe. 7. Vent pipe.

4. Oil-feed pipe.

Very thorough filtering results. On 1956-7 models a fabric-type filter with felt
element is omitted. Instead, a cylindrical filter of fine metal-gauze is secured in the
tank end of the feed-pipe union.
Always purchase engine oil in sealed containers or replenish from branded cabinets.
Specify clearly the brand and grade which you require, and refuse firmly but politely
the "just as good" type.

Suitable Engine Oils. To ensure easy starting, maximum performance and
minimum wear, the safest policy is to use one of the brands and grades officially
recommended by A.J.S. Motor Cycles. They recommend the use of one of the
following engine oils-
(a) Castrol "Grand Prix" (summer) or "XL" (winter).
(b) Mobiloil "D" (summer) or "A" (winter).
(c) Shell X-100 50 (summer) or X-100 30 (winter).
(d) B.P. Energol SAE 50 (summer) or B.P. Energol SAE 30 (winter).
(e) Esso 50 (summer) or Esso 30 (winter).

It should be noted that the above recommendations are not tabulated in any priority

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order. It is for the rider to choose which brand he prefers. All the five mentioned are
thoroughly sound.

Oil Level in Tank. Remove the filler cap and inspect the level of oil prior to every
ride. Always verify the level very carefully before a long run and top-up with suitable
engine oil (see previous paragraph) if necessary. Sufficient oil must be kept
circulating to ensure correct lubrication of the engine and its proper cooling.
Never allow the oil level to fall below the low level mark, otherwise the oil in
circulation is apt to become hot, dirty, and diluted. As far as possible maintain the
oil level at or near the top level mark on the outside of the tank (1952-7), but do not
a low the level to rise above this mark; or (1945-51) above 1 in. from the filler-cap
orifice. This is important for the following reason.
On stopping the engine, no further pump action occurs, but the oil continues to drain
into the sump from various parts of the engine. When the engine is subsequently
started there is obviously surplus oil accumulated in the sump and this is immediately
pumped back into the tank by the large-capacity scavenge end of the pump plunger.
The effect is to cause an excessive rise in the level of oil in the tank, and possibly oil
leakage via the tank air-vent (provided to avoid air locks).

Checking Oil Circulation. Verify the oil circulation before every run,
immediately after starting up the engine from cold. Remove the oil tank filler-cap and
observe the oil flow from the small spout (see Fig. 35) about 2 in. below the filler­cap orifice. If no oil can be seen emerging from the spout, raise the exhaust valve
lifter and stop the engine immediately.
The oil flow immediately after starting up the engine from cold should be steady.
An erratic or weak flow is abnormal and requires investigation. After a brief period
of warming up the engine, the surplus oil in the crankcase sump is disposed of, and
thereafter the oil flow from the spout of the return pipe decreases somewhat and may
become irregular. Some froth may be noticeable caused by the presence of air
bubbles, but this is normal and can be disregarded, once the engine gets into its
stride.
If you suddenly accelerate the engine and then close back the throttle, you may
observe first a marked decline, or even cessation, of the oil flow and then a
considerable increase in the flow.

No Pump Adjustment. The A.J.S. oil pump is capable of delivering the correct
volume of oil to the engine at all throttle openings. Consequently there is no
adjustment provided for the main oil supply. To ensure correct lubrication of the
engine, however, it is essential to keep the two end-caps of the plunger housing quite
airtight. Check the securing nuts periodically for tightness with a spa nner. (See also
page 57.)

Oil Supply to Inlet Valve Stem. The adjuster for the oil supply to the inlet valve

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stem comprises a needle-pointed screw (Fig. 34) situated on the off-side of the
cylinder head. If the engine is mechanically sound, the approximately correct setting
of the adjuster screw is one-sixth of a complete turn from the fully closed position.
Once the correct setting has been obtained, it should not be necessary to interfere
with the adjustment.

The adjuster screw is secured by a lock-nut, which prevents
accidental alteration of the adjustment. To increase or
decrease the oil supply to the inlet-valve stem, the adjuster
screw must be turned slightly anticlockwise or clockwise
respectively, after first loosening the lock-nut.
What symptoms indicate that an adjustment is called for?
An excessive oil supply is denoted by blue smoke at the
exhaust, high oil consumption, and a tendency for the
sparking plug to oil up and become dirty. An insufficient oil
supply is indicated by the inlet-valve stem developing a
mouse-like squeak.

The Exhaust Valve Stem. No adjustment is provided for
the oil supply to the exhaust-valve stem. The stem is
automatically lubricated by oil fed through a channel drilled in
the cylinder head. Surplus oil from the exhaust-valve stem

FIG. 37. GAUZE
FILTER INTEGRAL
WITH FEED PIPE
UNION

(1945-51 ONLY)

once every 5,000 miles. If a machine is only used for short runs, renew the oil every
three mo nths. Also clean the t ank filter (s). Before draining the oil tank, make sure
that your A.J.S. is level, with both wheels on the gr ound or with th e stand down.
Then to drain the tank, place a suitable receptacle below the drain plug to catch the
oil and unscrew the plug from the off- side or rear(1945-51)edge of the tank. Be
patient and allow all the oil to drain away. Having drained the oil tank, also remove
the drain plug from the bottom of the crankcase sump (on the off-side), and permit
any accumulation of oil to drain off. There will not be a large amount, but it is
desirable to remove what there is. A powerful magnetic filter is fitted to the
crankcase drain-plug on 1956 and later models and it is important to see that the
accumulation of any fine metallic particles is completely removed. Finally, make
sure that both drain plugs are replaced and firmly tightened.

and from the stem of the inlet valve is by-passed back into the
chamber responsible for lubricating the timing gears.

Changing the Oil. With a brand-new A.J.S. it is advisable to
empty the oil tank and replenish it with fresh oil after cove rin g
500 miles and again at 1,000 miles. After this, change the oil

The Magnetic Crankcase-Filter (1956-7). To obtain access to this filter for

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cleaning, it is only necessary to unscrew the crankcase drain-plug which embodies
the magnetic filter.
Forcibly wipe off with a greased rag all metal particles adhering to the magnetic
filter (they adhere strongly). If you place the filter on the bench see that the magnet
does not come into contact with large iron or steel objects, such as a vice, otherwise
some loss of magnetism may occur. Also avoid placing the magnet close to iron or
steel filings, which will be attracted to the magnetic filter and need removing.

The Tank Filters. Thorough and regular cleaning of the two filters in the oil tank
(one, 1956-7) is most important and must never be overlooked. It is best to remove
and clean the filters when the engine oil is changed. Advice on removing the filters
is given in subsequent paragraphs. As regards actual cleaning, this should be done
thoroughly with petrol, but do not attempt to remove the felt element of a large
cartridge-type filter from its tubular wire-cage, and do not use a flurry rag when
cleaning a gauze filter. Allow to dry afterwards. Inspect the cork washer fitted below
the hexagon cap of a fabric filter (Fig. 35) and renew the washer if it is not in perfect
condition. Also examine the felt element very carefully. Fit a new element if its ends
are at all distorted or perforated.
It should be observed that a choked gauze-filter can completely or partially starve the
engine of oil, since it is secured to the feed-pipe union and all oil entering the engine
has to pass through it.
On the other hand, choking of the above gauze can be caused only through
replenishing the tank with impure oil. The whole of the oil returned by the pump
from the engine to the tank is effectively cleaned by means of the large fabric or
gauze (1956-7) filter, assuming the felt or gauze (1956-7) element is sound. If the
felt element of a fabric filter is clogged up with impurities, excessive lubrication can
occur owing to resistance offered to the returning oil causing a "build-up" of oil in
the sump. Renew the filter element if its condition is poor.

To Remove Felt Element (1945-55). First raise (1945-7) the rear of the saddle after
removing the two saddle-spring securing bolts. On 1948 and later machines this is not
necessary.
Unscrew and remove the hexagonal cap from the oil tank filler-orifice. Next
withdraw the dished washer and the filter spring.
On 1945-53 models insert a finger inside the felt element and gently raise the
element until the top end touches the underneath of the saddle. Now encircle the filter
with the hand and exert sufficient upward pressure on the flexible saddle-top to
enable you to withdraw the filter without distorting it. Take great care not to kink or
damage the element when withdrawing it.

On 1954-5 models, after withdrawing the dished washer and filter spring, insert a

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finger in the exposed open end of the felt element and gently strain inward and
backward (rigid-frame models) to avoid fouling the saddle frame, or outward and
forward (spring-frame models) to avoid fouling the dualseat. Be most careful not to
kink the element when doing this.
The procedure for replacing the filter element is the reverse of that just described.
On a 1945-7 model, where the rear of the saddle is assumed to have been raised,
replace the saddle in its normal position and fit and securely tighten the two saddle­spring securing bolts.

To Remove Gauze Filter (1945-51). To remove a filter (Fig. 37) for cleaning
after draining the oil tank, the following procedure is necessary. Disconnect the oil­feed pipe from the union screwed into the base of the oil tank by unscrewing the
union nut from the pipe nearest the rear wheel. Spring the feed pipe away from the
union and then unscrew the union and remove this complete with the integral filter.
To replace the gauze filter, union, and feed pipe, reverse the above instructions.

To Remove Gauze Filter (1952-7). The small gauze filter on the delivery side is
not integral with a detachable union as on the 1945-51 models. Referring to Fid. 36,
first drain the oil tank and then (1952-6) free the oilfeed pipe from the rubber
connecting-sleeve on the small oil-feed pipe which projects from the base of the
tank. If the gauze filter comes away with the rubber connecting-sleeve (1954-6) or
feedpipe (1957), do not disturb it. If, however, the filter remains in the small pipe
attached to the tank, grasp the ringed open end and pull the filter out of the pipe.
Replace the filter in the reverse order of removal. On 1957 models all oil pipes are
of the Neophrene push-on type.

Splitting the Crankcase. Should it be necessary for any reason to separate the
crankcase halves, it is essential to remove the pump plunger (Fig. 33) first. Failure
to take this precaution will almost certainly result in damage being caused.

Removing Pump Plunger. Do not remove the oil-pump plu nger unnecessarily.
If you must remove it, first drain the oil tank as described on page 54. Also unscrew
the union nut securing the bottom end of the oil feed pipe from the pump housing
to the rocker-box. Remove both end-caps from the pump housing by undoing the
hexagon-headed securing bolts.
Just below the pump housing in front of the rear cap is the all-important guide
screw and pin. Remove these together (see Fig. 33), and push out from the front the
pump plunger and withdraw it from the rear end of the pump housing.

To Replace the Plunger. First make sure that the inside of the pump housing is

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clean, and check that the plunger itself is clean internally and externally. Oil the
plunger and gently push it into position. Its smaller end must enter the rear of the
pump housing, and the guide screw must next be fitted. Before replacing the guide
screw, make certain that the steel pin inside the hollow screw is fitted as indicated in
Fig. 33, or serious damage may be caused to the teeth of the pump plunger.
After replacing the guide screw, and while slowly tightening it, move the pump
plunger backwards and forwards until the end of the guide-screw pin is felt to
engage the profiled cam-groove at the rear end of the plunger. When this happens,
tighten the guide screw firmly, but on no account tighten before proper engagement
is obtained, otherwise stripping of the teeth on the timing-side engine main-shaft
and of the teeth on the plunger is liable to take place.
Fit the pump-housing front and rear end-caps and see that airtight joints are
obtained. The two paper washers must be in perfect condition. Renew them if they
are damaged in the slightest degree. Make certain when fitting the paper washer for
the front end-cap that the small oil hole in the cap itself is not obstructed.

The Pump Housing End-caps. It is advisable to apply some liquid jointing
compound to one side of each paper washer. This side must be fitted in contact with
the end-cap. To ensure an airtight joint at each end-cap, it is essential to see that the
securing bolts are tightened down evenly and firmly. Tightening should always be
effected in a diagonal order. Also occasionally check the delivery and return-pipe
union nuts for tightness.

Magneto Bearings. These are initially packed with grease by the makers during
assembly and further greasing should not be necessary for 10,000-15,000 miles.
When a general overhaul becomes necessary it is desirable to remove the magneto
and return it to Joseph Lucas, Ltd. of Birmingham, 19, or to one of their service
depots, for thorough servicing. No grease nipples are fitted, but the contact-breaker
requires periodical oiling.

The Contact-breaker (Face-cam Type). The cam and tappet of the face-cam
type contact-breaker (Fig. 38) require lubrication approximately every 3,000 miles.
To effect such lubrication, remove the complete contact-breaker as described below.
First release the spring blade and take off the contact-breaker cover. Now, referring
to Figs 38 and 39, remove the screw (E) and the spring washer retaining the spring
arm (A) to the body (L) of the contact-breaker, and detach the curved backing spring
(D) and the spring arm (A). Next unscrew the screw (B) carrying the lubrication
wick, and remove the insulating bush (fibre).

Straighten the tab on the locking plate (J) situated behind the head of the contact-

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breaker securing screw (H), and with the spanner remove screw (H). Then lever off
the contact-breaker body (L) from the armature-shaft extension.

FIG. 38. FACE CAM CONTACT-BREAKER OF LUCAS ROTATING­ARMATURE MAGNETO SHOWN ASSEMBLED

This type of contact-breaker is provided on the magnetos of all 1945-53 machi nes and 1 954 35 0 c.c. machi nes
with manual ignition-control. The various parts are shown dismantled in Fig. 39. The rotating- magnet
magneto (1954 500 c.c. and 1955-7 models) is shown in Fig. 46.)

After completely removing the contact-breaker, saturate the wick, mounted in the
core of the carrying screw (8), with a few drops of thin machine oil. Push from the
contact-breaker body (L) the tappet (K) and wipe the tappet clean with a soft cloth.
Smear a little thin machine-oil on the tappet and replace it in the body.
To assemble the face-cam type contact-breaker, proceed in the reverse order of
dismantling. Make sure that the curved backing spring (D) is replaced so that the
curved part is on the outside. The foregoing does not apply to rotating-magnet
magnetos.

The Contact-breaker (Rotating-magnet Magneto). On 1954 500 c.c. and all
later models fitted with a Lucas type SR-1 magneto having automatic ignition­control mechanism on the driving side (behind a bulge on the magneto chain-case
cover), about every 3,000 miles undo the three captive screws and remove the
moulded end-cover. Loosen the nut securing the contact-breaker spring and lift off
the contact-breaker lever (see Fig. 46). The spring is slotted to facilitate removal.
Then smear the pivot pin with a little Mobilgrease No. 2 or a similar grease.

The Magneto Chain. The magneto driving-chain (enclosed in a chain case on the

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off-side of the engine) is not automatically lubricated like the dynamo chain. It is
necessary to add some grease about every 1,000 miles. On 1945-51 models inject
some Mobilgrease No. 2 or Esso Fluid Grease through the grease nipple provided on
the outside of the chain-case cover On 1952 and all subsequent models, the magnet o
chain requires occasional replenishment with one of the two above-mentioned
greases. Remove the chain-case cover, and apply suitable grease generously to the
chain. Also with a thin-metal strip, work some of the grease well into the automatic
ignition-control mechanism (1954 onwards).

FIG. 39. FACE CAM CONTACT-BREAKER OF LUCAS ROTATING-
ARMATURE MAGNETO SHOWN DISMANTLED

The same contact-breaker is shown assembled in Fig. 38.

MOTOR-CYCLE LUBRICATION

The Dynamo Bearings. The armature bearings of the (Lucas type E3 AR, 1945-

50; E3-N, 1951 onwards) dynamo, as on the magneto, are packed with grease by the
makers on assembly and this should suffice for at least 10,000 miles running, or
until it is necessary to make a general overhaul, when the dynamo should be
removed and returned to Joseph Lucas, Ltd., or to a Lucas service depot for
thorough cleaning, overhaul, and lubrication.

The Dynamo Driving Chain. The separate Lucas dynamo is chain-driven from
the engine shaft by a chain which is completely enclosed in the oilbath chain case
containing the primary chain. Therefore, provided the oil-bath chain case is kept
properly replenished, no individual attention to the dynamo chain is necessary. The
replenishment of the oil-bath is dealt with on page 62.

FIG. 40. WHEN AND WHERE TO LUBRICATE (1945 ONWARDS)

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The above lubrication chart (showing a 1957 Model 18S) applies to all 1945 and later O.H.V. singl es, but note
the following points: on 1945-51 models the chain-driven magneto is mount ed behind the cylinder and the
chain-case has a grease nipple; on 1945-55 models a different type oil tank (see Fig. 35) with fabric- type main
filter is specified

FIG. 41. THE 1952-6 BURMAN GEARBOX
KEY TO FIG. 41

1. Clutch-cable adjuster. 2. Filler cap. 3. Oil-level plug .

Burman Gearbox Lubrication. A.J.S. Motor Cycles advise the use of summer
grade engine oil (see page 52) for the four-speed heavyweight Burman gearbox on
the 1948-57 models. On 1945-7 machines, however, light grease is recommended
for gearbox lubrication. On no account must thick grease be used.

KEY TO FIG. 40

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Item Description
No.

1 oil tank

2 Inlet-valve stem
3 Lucas Magneto

4 Magneto chain

5 Gearbox

6 Primary chain
7 Secondary chain

8 Front and rear hubs
9 The brakes .

10 Steering head

11 Front-brake cable

12 Rear-brake pedal.

13 Speedometer

14 Handlebar levers.

15 Stands

16 Front forks.

17 Spring frame

Lubrication Required Page
ref.

Before each run check oil circulation and level. 55, 54

Top-up as required. Every 5.000 miles
change the oil and clean the filter(s). Also
drain oil sump.

If necessary, adjust the oil supply. 55

Every 3.000 miles apply a few drops of thin oil 57, 58

to the contact-breaker wick and tappet
(face-cam C.B.). or smear a little grease on
the lever pivot-pin (rotating-magnet magneto).
Every 1,000 miles inject a little grease (1945-51 58
models) with the grease gun. or occasionally
repack the chain with grease (1952 onwards).
Every 1.000 miles inject 2 fluid ounces of light 60-62

grease (1945-7). or top-up with summer
grade engine oil (1948 onwards) to the
correct level. Every 5.000 miles change the
lubricant.
Every 500 miles check level in oil-bath and top- 62
up if necessary to filler-cap orifice.

Every 500 miles apply some engine oil if dry. 63
In wet weather, remove, clean, and grease
every 1.000 miles.

Every 1.000 miles apply the grease gun to the 63
hub nipples.
Every 1.000 miles apply the grease gun to the 64

expander-bush nipples. Weekly oil the
brake linkage. Also every 3.000 miles
grease the rear-brake pedal.

Every 1.000 miles grease both bearings with 64

the grease gun.
Weekly oil the exposed end. 64

Every 3.000 miles apply the grease gun to the 64
heel nipple.
Every 3.000 miles inject grease through the 64

nipple on top of the speedometer gearbox.
Weekly apply a little oil to all moving parts. 64

Inject some oil into the Fables (where nipples
are provided).
Occasionally oil fulcrum bolts. 65
Every 5,000 miles (3,000 miles, 1945-7) check 65-6 8
the hydraulic fluid content of both/Tele­draulic legs," and top-up if necessary.

If really necessary, replenish the oil reservoir 68-69
for the "swinging arm" bearings, and also
the rear-suspension units.

Suitable grease for 1945-7 gearboxes, and for lubricating 1945 and later motor-cycle

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parts by means of the grease nipples provided, are as follows-
(1) Castrolease Heavy (Medium for 1945-7 gearbox).
(2) Mobilgrease No. 4 (No. 2 for 1945-7 gearbox).
(3) Shell Retinax Grease C.D. or A.
(4) B.P. Energrease C3.
(5) Esso (pressure gun) Grease.
Do not completely fill up the gearbox with engine oil or light grease. Under normal
conditions it is sufficient to top-up the lubricant every 1,000 miles with 2 fluid oz. of
light grease or with a little summer-grade engine oil (1948-57 models) via the grea se
nipple on the kick-starter case or through the filler-cap orifice (see Fig. 41)
respectively. Excessive filling will result in leakage.
All 1952-6 Burman gearboxes and the 1957 A.M.C. gearboxes have an oil-level
plug (3, Fig. 41) located close to the kick-starter spindle; to top-up the gearbox to
the maximum permissible level (content: 1 pt.), it is only necessary to pour in engine
oil through the filler-cap orifice until it begins to trickle from the level-plug hole.
On the 1952-6 Burman fourspeed gearboxes the filler cap comprises a slotted and
threaded circular-cap, but on the 1957 A.M.C. gearboxes the filler cap is replaced by
a circular cover secured by two small screws. Removal of the circular cover,
incidentally, gives access to the clutch thrust-mechanism.

Changing the Gearbox Oil. After the first 500 miles and thereafter about every
5,000 miles change the lubricant in the gearbox. The light grease or engine oil
(1948-57 models) should be drained completely, the Burman gearbox flushed out
with a suitable flushing oil and afterwards replenished with 1 lb. 14 oz. of grease
(1945-7 boxes), or with 1 pint of engine oil (1948 onwards).
The screwed drain-plug is located low down at the rear of the gearbox shell. Where
a non-fluid lubricant (light grease) is used, it may be found somewhat difficult to
drain the gearbox thoroughly by removing the drain plug only. The best plan here is
to remove the foot-change cover and the kick-starter case. Before replenishing the
gearbox make sure that the drain plug is replaced and firmly tightened.

Primary Chain Lubrication. Remove the inspection cap from the oilbath chain
case about every 500 miles and observe the level of oil. On no account must the oil
level be permitted to fall below 3/16 in. from the bottom edge of the inspection-cap
orifice, with the machine standing vertically on level ground. The correct amount of
oil is present when its surface is level with the orifice.
If the oil level is too low, some harshness in the primary transmission generally
develops, except on 1957 models where a sliding oil-seal in the form of two steel
discs surrounds the gearbox mainshaft. Top-up the oilbath chain case as required
and when necessary, using one of the brands of the summer-grade oils mentioned on
page 52. Lubrication must not be neglected, for the oil-bath is responsible for
lubricating: (a) the primary chain, (b) the dynamo chain, and (c) the engine shaft
shock-absorber.

The Oil-bath Inspection Cap. To remove the cap, unscrew the knurled screw

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approximately four turns. Then slide the cap sideways until it is Possible to slip the
back plate through the orifice and remove the complete cap assembl y .
To prevent the risk of the filler cap, or inspection cap, being lost while riding, it is
important to centralize the cork washer before firmly tightening the knurled
retaining screw. Do not forget this when replacing the inspection cap.

Secondary Chain Lubrication. About every 500 miles examine the condition of
the secondary chain. If the chain is in a dry state, turn the rear wheel by hand and
apply some engine oil with a brush or oil-can. About every 1,000 miles in wet
weather, it is advisable to remove the chain from the sprockets and clean and
lubricate it in the following manner-
(1) Clean the chain thoroughly with paraffin.
(2) Hang up the chain and allow to dry.
(3) Immerse the chain for at least ten minutes in a suitable receptacle containing
Mobilgrease No. 2, B.P. Energol A.O., Esso Fluid Grease, or Castrolease Grease
Graphited. The grease should be heated until just fluid and maintained in this state
during the period of chain immersion.
Having lubricated the chain, fit it to the gearbox and rear-wheel sprockets. It is
permissible to lubricate the chain, using engine oil instead of one of the greases
mentioned, but this substitute is not so good. Allow the chain to soak for at least an
hour where engine oil is used.

Filling Grease Gun. The grease gun (Part No.017246) provided with the tool kit
must be applied periodically to all grease nipples provided on the machine.
Suitable greases to use for various motor-cycle parts are those recommended on
page 61. The grease gun must be charged so that the grease is on the top side of the
piston. Special grease canisters are available with loose collars provided with holes.
To charge the grease gun from one of these canisters, place the barrel of the gun
over the hole in the central floating plate and press downwards firmly. Turn the
grease gun and at the same time remove it from the floating plate. This should
charge the grease gun so that the grease is flush with the top of the barrel. Having
charged the grease gun, replace its screwed top-cap. If no grease canister of the type
referred to is available, charge the grease gun by hand, using a suitable lath or
similar implement.

The Wheel Hubs. On new machines the hubs of both wheels are packed with
grease. To prevent mud and water entering the hubs, and to ensure correct
lubrication, inject some grease through the nipple (accessible through the hole in the
hub disc (1955 onwards)) of each hub about every 1,000 miles. Avoid excessive
lubrication, or some of the grease may get on to the brake linings and impair the
efficiency of the brakes.

Steering Head Lubrication. Apply the grease gun sparingly to the grease nipple

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in the head lug of the frame about every 1,000 miles. Also grease the nipple on the
right-hand side of the handlebar lug at the same time.

The Front and Rear Brakes. Inject a little grease about every 1,000 miles
through a grease nipple provided on each brake cover-plate for the expander bush.
About every 3,000 miles apply the grease gun to the nipple in the heel of the rear­brake pedal (shown at (2) in Fig. 62).
Smear a few drops of engine oil weekly on the yoke-end pins at the front and rear
ends of the rear-brake rod. Do not forget the threaded portion of the rod to which
the hand adjuster is fitted. Also remember the exposed end of the front-brake cable.

The Rear Brake-drum Bearing (1955-7 Spring Frame Models). On the "springers"
with full-width light-alloy rear hubs, the ball bearing supporting the brake drum is
packed with grease during initial assembly. No further lubrication should be
required until it is necessary to undertake a general overhaul. The bearing should
then be dismantled and repacked with fresh grease (see pages 61 and 137).

Speedometer-Gearbox Lubrication. To ensure smooth and efficient running,
grease the speedometer gearbox every 3,000 miles. The gearbox is attached to the
rear-wheel spindle and the grease nipple is located on top of the speedometer
gearbox as shown in Figs. 75 and 76. No further lubrication is required beyond the
above-mentioned attention.

The Throttle Twist-grip. Stiffness sometimes develops and this spoils sensitive
control of the throttle. To rectify stiffness is quite simple, and the following
procedure should be adopted.
(1) Remove both the screws which retain the halves of the twist-grip clip.
(2) Withdraw the twist-grip from the end of the handlebars.
(3) Smear some grease on the off-side part of the handlebars over which the twist­grip fits.
(4) Smear some grease on the friction spring, and also on the drum on which the
internal wire is wound.
(5) Replace the twist-grip on the end of the handlebars.
(6) Fit the two screws retaining the halves of the twist-grip clip and firmly tighten
the screws.

The Handlebar Levers. It is advisable to apply a little engine oil monthly to all
the moving parts of the handlebar levers. This will reduce friction and keep the
controls responsive and easy to operate.

On 1954 and later models the control cables for the throttle slide and clutch lever

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have a conveniently situated nipple for the injection of engine oil by means of a
grease gun. Some engine oil should be injected at the first indication of jerky or stiff
action. When using the gun, hold it as nearly vertical as possible, with the nozzle
facing downward.

The Stands. Occasionally lubricate the stand fulcrum-bolts; apply some engine oil
to them with an oil can. There are several small parts on the machine where only a
little movement occurs. All such parts should be similarly lubricated. This will
facilitate free movement and prevent rusting. The main parts of the A.J.S. requiring
attention are indicated in the lubrication chart on page 61.

Sidecar Chassis. Do not forget to lubricate the sidecar chassis. Several grease
nipples are provided for the purpose.

Hydraulic Fluids for "Teledraulic" FrontForks. The 1945-7 "Teledraulic"
front forks and 1948-57 type, modified and simplified internally, require no actual
lubrication. It is necessary, however, occasionally to check the hydraulic fluid
content of each fork leg (6 1/2 fluid oz. on 1945-7 forks, 10 oz. for 1948-50, 6 ½ oz.
for 1951 onwards); top-up if necessary, as described in later paragraphs of this
chapter.
Below are specified suitable types of fluid for the A.J.S. hydraulic dampers-
(1) Wakefield's "Castrolite."
(2) Mobiloil "Arctic."
(3) Shell X-100 20.
(4) B.P. Energol SAE 20.
(5) Essolube "20."

Level of Fluid (1945-7 "Teledraulic" Front Forks). It is desirable to check the
fluid level every 3,000 miles. Position your A.J.S. so that it is resting on both
wheels and is quite vertical. To maintain it in this position, insert packing beneath
both footrests. Unscrew the two hexagon plugs shown at (A) in Fig. 2. Pull each
plug (A) upwards to its maximum extent and thereby expose the fork damping-rod
attached to the plug.
By "pumping" action eject any hydraulic fluid trapped in the tubes above the damper
valves. Work each plug and damping rod up and down several times. Pause for two
7ninutes to permit ejected fluid to drain down to the main supply of damping fluid.
Remove the two fluid-level plugs and their fibre washers from the fork slides. The
plugs are situated just beneath the securing bolts for the front mudguard-bridge.
Some hydraulic fluid should just ooze from the holes of the fluid-level plugs if the
hydraulic fluid content of the forks is correct. Should no fluid be seen to ooze out
from the holes, it is necessary to top-up each fork leg as described below.

Topping-up (1945-7 "Teledraulic" Front Forks). It is assumed that the two

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fluid-level plugs are still removed. To top-up each leg of the "Teledraulic" front
forks, the following procedure is required-
(1) Pour about two table spoonfuls (equivalent to one fluid ounce) of hydraulic flu id
down each fork-leg inner-tube from the top end.
(2) Work the top plug and attached damper rod up and down several times.
(3) Wait for two minutes to allow hydraulic fluid to ooze from the fluid level hole.
(4) If no excess hydraulic fluid oozes from the fluid-level hole, pour another fluid
ounce of this medium down the inner tube of the fork leg.
(5) Having added further fluid, work the top plug and attached damper rod up and
down several times, as previously. During all such "pumping" action, use the
fingers only and make the upward strokes as sharply as possible.
(6) If still no fluid oozes from the fluid-level plug hole, investigate the reason
carefully and rectify any defect responsible.
(7) As soon as hydraulic fluid is observed to ooze out of the level-plug hole, this
indicates that the fluid content of the fork leg is correct, and the plugs can be replaced
as referred to below.
(8) Replace the fluid-level plug on the inner side of the fork-leg slider. Do not forget
to fit the fibre washer before tightening the plug with a screwdriver.
(9) Fit the plug to the top of the fork-leg inner-tube and firmly tighten with a spanner.

Hydraulic Fluid Content (1948-57 "Teledraulic" Front Forks). It is wise
every 5,000 miles to check the hydraulic-fluid content of each front fork-leg.
Before beginning this check, it is necessary to see that your A.J.S. is quite vertical,
with the front wheel raised clear of the ground (weight on both wheels, 1951-7
models).
Place a suitable box beneath each footrest. Remove the two hexagon-headed plugs,
shown at (A) in Fig. 2, from the tops of the fork-leg inner tubes, after levering off (1

955) the snap-on dome caps, or removing the rubber grommets (1956-7).
To determine the fluid content of each fork leg, remove the drain plug from the base
of the fork-leg slider and permit the hydraulic fluid to drain off into a graduated
measuring jug or other vessel having a capacity of at least 10 fluid ounces. Most of
the fluid will drain off, but not all of it will do so.
Replace the drain plug in the base of the fork-leg slider, and on 1948-50 models
work the forks up and down several times. On 1951-7 front forks the damper rod is
attached to the hexagon-headed plug at the top of each fork leg and it is necessary to
work each damper rod (instead of the forks) up and down, employing a pumping
action. Hold the top plug with the fingers only, and make very sharp upward
strokes.

Wait two minutes and then remove the drain plug a second time and catch any

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further hydraulic fluid which may drain off into the graduated vessel already
containing most of the fluid. It may be necessary to repeat the draining procedure
(including working the forks or top plugs up and down) several times to ensure that
the maximum quantity of hydraulic fluid is drained off into the graduated vessel.
Note the total amount of fluid extracted. It is not possible to extract in this manner
the whole content of each leg (10 fluid ounces, 1948-50; 6 1/2 fluid ounces, 1951-7),
but the amount drained off and measured should total 9½ fluid ounces or 6 fluid
ounces respectively.

FIG. 42. SHOWING DETAILS OF THE A.J.S. SPRING FRAME
"Swinging arm" type rear-suspension was first introduced in 1949 and is specified on Models 16MS and
18S. The rear-suspension units rarely need any attention.

Topping-up (1948-57 "Teledraulic" Front Forks). The checking of the

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hydraulic-fluid content and the topping-up of each fork leg should be effected in one
continuous operation. Deal with each fork leg individually. It is assumed that the
fluid content of the leg has already been determined.
Then top-up as follows-
(1) If the total amount of hydraulic fluid extracted from the fork leg measures
exactly 9 1/2 fluid ounces (1948-50) or 6 fluid ounces (1951-7), no topping-up is
necessary. If the amount is less than the appropriate quantity just stated, add
hydraulic fluid (of the type already in use) to the graduated vessel until the total
amount of fluid measures exactly 9 1/2 fluid ounces or 6 fluid ounces, as the case
may be.
(2) Replace the drain plug in the base of the fork slider.
(3) Pour the 9 1/2 or 6 fluid ounces contained in the graduated vessel into the t op of
the fork inner-tube.
(4) On 1948-50 models, verify that the fork leg is fully extended.
(5) Replace the hexagon-headed top plug (and rubber washer), and firmly tighten
the plug. Also replace the snap-on dome cap (1955) or rubber grommet (1956-7). It
is important to note that where 1948-57 "Teledraulic" front forks have been
completely stripped down (necessarily incurring the removal of all hydraulic fluid), it
is essential after assembly to top-up each fork leg with the full 10 fluid ounces (1948-

50) or 6 1/2 fluid ounces (1951-7), not the quantities (1/2 fluid ounce less) just
quoted for topping-up.

The "Swinging Arm." The "swinging arm" assembly in whose rear end the rear
wheel is mounted is hinged just behind the gearbox, and the "swinging arm" fork­hinge plain bearings (see Fig. 42) are automatically lubricated from a reservoir
containing 1 1/2 fluid ounces (42.6 c.c.) of engine oil.* This should suffice to
lubricate the bearings for an almost indefinite period. Slight oil leakage may occur
on a new machine (or where the reservoir has been replenished) but this is of no
significance and stops after a few hundred miles have been covered. If
replenishment should ever become necessary, remove the small screw from the off­side hinge bearingcap and top-up the oil reservoir with engine oil (see page 52) to
the level of the screw orifice.

* Heavy gear oil (SAE 140) is recommended by the makers for 1952 and later models.

"Teledraulic" Rear-Suspension Units (1949-56). The rear-suspension units

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have hydraulic damping springs of almost identical design to that used for the
"Teledraulic" front forks. But only if leakage of hydraulic fluid occurs (most
unlikely) is it necessary to replenish the fork legs with the correct amount of fluid.
Should the leg action become excessively lively, it is possible that some loss of
damping fluid is responsible, but unless you are in serious doubt as to the correct
functioning of the spring frame, you are advised to leave well alone.
The hydraulic fluid (oil) content of each "Teledraulic" rear leg can be checked in
accordance with the instructions given in the maker's instruction book. The correct
fluids to use are those specified on page 65. For the spring frame on all 1949-50
models each fork leg should contain exactly 1 3/4 fluid ounces (50 c.c), but on the
1951 and later spring frames the recommended quantity is 85 c.c. or a little below 3
fluid ounces. On no account must the oil content exceed 90 c.c.

Girling Rear-Suspension Units (1957). These proprietary units are sealed by the
makers and do not require to be topped-up. During initial assembly their springs are
lubricated and sufficient hydraulic fluid inserted in the damper units to last until the
Girling units require to be renewed.
Occasionally clean and grease the cam-ring adjusters provided to give three
different spring tensions. If the movement of the telescopic legs is accompanied by
a rubbing noise or squeaking, remove the two half circlips securing each top cover­tube, remove the tube, and apply some grease to the outside diameter of the spring.

CHAPTER V

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GENERAL MAINTENANCE

This chapter contains full maintenance instructions for all 1945-57 touring singles.
Some instructions, however, have already been included in Chapters II-IV.
Appropriate cross-references to these earlier chapters are therefore also included.

A.J.S. Repairs and Spares. When you have occasi on t o fo rwa r d or deli ve r part s to
the manufacturers* (either for repair or as patterns) always attach to each part a
label on which is written clearly your full name and address. To ensure quick
attention, all correspondence concerning spares and technical advice should be
written on separate sheets, each bearing your name and address.
Always quote the complete engine number or frame number, according to the nature
of the part involved. The frame number will be found marked on the off-side of the
saddle lug (see page 1). The engine number (with letter prefix) will be found on the
near-side of the crankcase.
There are numerous firms in the United Kingdom who can supply A.J.S. spares over
the counter, and many who specialize in the repair of engines and gearboxes.
Useful addresses may be found in the advertisement pages of The Motor Cycle and
Motor Cycling. If taking a machine to Plumstead, first make an appointment.

Some London Accessory Firms. Among reputable London firms (some of which
have provincial branches) handling motor-cycle accessories, equipment spares,
tools, clothing, etc. may be mentioned: Whitbys of Acton, Ltd.; Claude Rye, Ltd.;
E.S. Motors; The Halford Cycle Co., Ltd.; Turner's Stores; James Grose, Ltd.;
Marble Arch Motor Supplies, Ltd.; Pride & Clarke, Ltd.; and George Grose, Ltd.

ENGINE MAINTENANCE

Items for Maintenance. For engine maintenance there are certain items which

you must have handy in the lock-up or garage. These include: a can of paraffin for
cleaning purposes; a stiff brush for scouring dirt off the crankcase; a tin of suitable
engine oil (see page 52); a canister of grease;

The A.J.S. Service and Repair Dept. is in Burrage Grove. Plumstead. London. S.E.18.

a small oil-can containing some engine oil; a receptacle for oil when draining the oil

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tank and oil sump; a pair or some jars for washing engine parts in; some non-fluffy
rags; valve-grinding paste such as Richford's (coarse and fine); some fine emery
cloth; a set of engine gaskets (see illustrated Spares List); some jointing compound; a
pair of new gudgeon-pin circlips; and some good hand cleanser, such as "Gre­solvent."

Tools Required. The A.J.S. tool kit is adequate for any normal stripping down
and assembly job and should prove sufficient for routine maintenance and overhaul.
It is also necessary for maintenance to obtain a suitable feeler gauge for checking the
sparking plug gap (see page 73), an A.J.S. valve-spring compressor (for 1949 and
subsequent engines with hairpin valve springs), and a valve holder for grinding in
the valves. It is also desirable to obtain a wire-brush for cleaning sparking plugs.
Should you decide to undertake as much repair work as possible in addition to
routine maintenance, stripping-down, and assembly, it is desirable to rig up a
suitable bench, complete with vice, and to purchase some extra tools (various A.J.S.
service tools are available).
To begin, it is a good plan to buy a medium-weight hammer, a hand-drill and an
assortment of twist-drills, a hacksaw, some large and small (smooth and rough) files,
and a good soldering outfit for the repair of control cables. Repair work is beyond
the scope of this handbook, and you are not advised to tackle such work unless you
have fair technical knowledge and skill in handling tools.

Engine Lubrication. Detailed instructions on lubricating the A.J.S. engine are
given in Chapter IV. Attend to lubrication points 1 to 4 indicated in the Lubrication
Chart on page 60.

The Amal Carburettor. For comprehensive advice on how to maintain correct
carburation, refer to the instructions given in Chapter II.

Keep your Engine Clean. Keep your engine clean externally as well as
internally. By so doing you enhance pride of ownership and obtain other
advantages. Dirt is apt to mask defects and can accidentally enter the engine when it
is being stripped down. It will also make rusting more likely. Rusted cylinder and
cylinder head fins, besides being an eyesore, are detrimental to efficient dispersion
of heat by radiation. They should be clean and black. On the A.J.S. they are stove
enamelled black (except 1951-7 light-alloy cylinder heads).
To clean the cylinder and cylinder-head fins, use a stiff brush dipped in paraffin.
If the stove-enamelling has worn away, paint the fins with a good proprietary
cylinder black. Clean the aluminium alloy and bright surfaces with rags and
paraffin, assisted by brushes where necessary, and scour off the filth from the lower
part of the crankcase by means of stiff brushes and paraffin. Thorough cleaning may
take some time, but it is well worth while.

Check Nuts for Tightness Occasionally. On a new A.J.S. where some initial

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bedding-down occurs, it is advisable to check all external nuts and bolts for
tightness fairly frequently. After the running-in period is completed it is a good
habit to check the external nuts regularly every 3,000 miles. Pay special attention to
the cylinder nuts, the nuts on the engine plates, and the union nuts for the pipe
connexions.

THE IGNITION SYSTEM

The ignition system comprises a 14 mm. sparking plug and a Lucas rotating­armature type magneto (1945-53 models) or a Lucas rotatingmagnet type magneto
(1954 onwards). The magneto on all 1952 and later models is mounted in front of
the cylinder to facilitate removal of the dynamo. Manual ignition-control is
provided except on 1954 and subsequent models having a Lucas type SR-1 rotating­magnet magneto (see page 79) with automatic ignition-control mechanism on the
driving side. On all machines the magneto is chain-driven.

Suitable Sparking Plugs. To obtain maximum engine performance throughout
the throttle range, plus easy starting, it is essential always to run on a suitable type of
sparking plug. Three reliable makes of sparking plugs are the K.L.G., the Lodge,
and the Champion. Suitable types are
K.L.G. - Fit a three-point, detachable type F80, or FE80 (1951 onwards), or else the
appropriate watertight version (see page 73).
LODGE - Fit a three-point, detachable type H14 or a type HLN on all 1951 and later
models.
CHAMPION - Fit a non-detachable type L-10 (1945-6 350 c.c), L-10S (1945-6 500
c.c, all 1947-9 models), or type NA-8 (all 1950 and later models).

"Ignition Suppression" Plugs. To meet special legislation concerning sparking
plugs fitted to new machines (see page 2), various plugs incorporating a resistor are
available. A good example is the K.L.G. Special plugs of this make have the letter
"R" after the type number (e.g. F80R). Champion plugs of the built-in suppressor
type have the prefix "X" (e.g. XL-10, XNA-8, etc.). While it is not compulsory to fit
a "suppressor" type plug to a machine registered prior to 2nd July, 1953, it is
recommended that this be done, as "suppressor" plugs besides causing no annoyance
to "viewers" and "listeners," also have longer-wearing electrodes. An alternative to
fitting a plug with a built-in ignition supressor is to fit to the existing plug a terminal
cover (e.g. the Lodge type M90X, the K.L.G. type PS or SS, or the Champion)
embodying a resistor.

Weatherproof Sparking Plugs. All-weather riders usually find it ad vantageous

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to fit a weatherproof plug terminal-cover or (in the event of plug renewal being
required) to fit a watertight sparking plug such as the K.L.G. type. Two reliab le and
reasonably pr iced we ath erpr oof sp ark ing p lug t erm inal covers are the Lodge and the
K.L.G.
K.L.G. watertight sparking plugs have the prefix "W" (e.g. WF8, WFE80), and they
are not expensive.

The Sparking Plug Gap. It is advisable to check the gap between the electrodes
of the sparking plug about every 3,000 miles. The correct gap is 0.018-0.022 in.,
and it is advisable to re-gap the plug if burning of the points has increased the gap to
over 0.022 in. When re-gapping a plug it is desirable for obvious reasons to set its
gap at or near the bottom limit.
Check the gap with a suitable feeler gauge (a wire gauge if the points are not very
accessible). The gauge should be a nice sliding fit. When adjusting the gap,

FIG. 43. THE BEST WAY TO RE-GAP A PLUG

never attempt to bend or tap the centre electrode. Use a plug re-gapping tool (see Fig.

43), a small pair of snipe-nose pliers, or a small screwdriver to bend the outside
(earth) electrode(s). Tapping the outer electrode(s) inwards to reduce the gap is
permissible, if the plug is held in a vice and a light hammer and copper drift are
used. When the plug has to be thoroughly cleaned, this should be done as described
below, and the plug re-gapped afterwards.

Cleaning the Sparking Plug. If carburation is correct (see page 15) and
excessive oil is not entering the combustion chamber, it should not be necessary to
dismantle and clean the sparking plug thoroughly more often than once about every
3,000 miles. When running-in a new or rebored engine, however, it is advisable to
remove and check the plug for cleanliness at intervals of about 500 miles.
Quick cleaning of a plug can be done by brushing the points and lightly rubbing their
firing sides with some smooth emery-cloth. Thorough cleaning (internal and
external), however, is not possible without dismantling the plug (see below).

To Clean K.L.G. and Lodge Plugs. Fig. 44 shows a typical detachable type

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(K.L.G.) sparking plug dismantled for thorough cleaning. To dismantle a
detachable-type plug, grip the smaller hexagon on the gland nut (B) in a vice, with
the plug upside down. Be most careful not to exert any pressure on the hexagon
faces. Then with the plug box-spanner, or a suitable ring spanner, unscrew the large
hexagon (E) on the plug body. Alternatively use two spanners to unscrew the gland
nut from the plug body. The centre electrode (F) with its insulation, comprising the
insulated electrode assembly (A), can now be detached from the gland nut. Take care
not to lose the internal sealing washer (H).

To clean the insulation, wipe it clean with a cloth soaked in
petrol or paraffin. If the insulation is coated with hard
carbon deposits, remove these with some fairly coarse
glass-paper and wash again, but make no attempt to scrape
off the deposits. The internal sealing washer (H) and the
surfaces on the insulator, and in the metal body on which
this washer rests, are very important as they prevent gas­leakage through the plug. Therefore wipe them only with a
rag soaked in petrol or paraffin. Any damage caused while
dismantling will render the plug unserviceable.
To clean the metal parts (plug body and gland nut), wipe
them clean with petrol, or, if necessary, scrape off the
deposits with a small knife, or use a wire brush. Afterwards
rinse the parts in petrol. The gland nut seldom gets very
fouled, but the inside of the plug body may be very dirty,
and the same may apply to the external threads of the pl ug.
Clean and polish the points see Fig. 44) of the centre and

FIG. 44. DETACHABLE
TYPE SPARKING PL UG
(K.L.G.)
The gland nut B and the
internal washer H are shown
still in position on the
insulation.

centre electrode and insulation are positioned centrally in the body bore. If not,
remove, re-position by rotating the centre a quarter of a turn, and re-assemble.
Do not attempt to force into position or bend. Tighten the gland nut into the plug
body just sufficiently to give a gastight joint. Do no t use an o pen-ended s panner.
Finally verify that the plug gap is correct.

outside (earth) electrodes (F) and (G) with some fine emery­cloth.
See that there is no dirt or grit lodged between the body of
the plug and the insulation, and particularly on the internal
sealing-washer and all contacting faces. Smear a little thin
oil on the internal washer and make sure that it seats
properly. When assembling the sparking plug, see that the

To Clean Champion Plugs. A Champion non-detachable plug such as the L-10S

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cannot be dismantled and cleaned like the detachable-type Lodge and K.L.G. plugs.
Quick cleaning is, of course, done in the same manner (see page 73). The best
method of cleaning a Champion plug thoroughly is to take it to a nearby garage
having an "air-blast" unit. In a matter of a few minutes the plug can be thoroughly
cleaned of all deposits, washed, and tested for sparking at a pressure exceeding 100
lb. per sq. in.
If the above method of cleaning is not available, remove the plug from the engine,
pour some petrol down between the insulated centre electrode and the plug body,
and set fire to the plug. Alternatively, burn the plug clean with some oily rag.
To assist cleaning, use a small wire brush. Wipe the tip and outside of the
insulation thoroughly clean. After removing all carbon, polish the electrodes with
some fine emery-cloth. Finally, check the plug gap (0.018 in. -0.022 in.).

Fitting a Plug. Before replacing the plug, renew the copper washer if it is worn or
flattened, and clean the plug threads. It is a good plan to coat the threads with some
graphite paste before replacing the plug. Screw the plug home by hand as far as
possible, and always use the plug spanner in the tool kit for final tightening. The use
of excessive force is undesirable and can cause distortion.

To Check Contact-breaker Gap (1945-53 Models). Normally it should be
sufficient to check the gap between the contacts of the contact-breaker about every
2,500 miles. Where the magneto or the contact-breaker is brand-new, however,
some bedding-down occurs, and it is advisable to check the gap after covering
approximately 500 miles. An incorrect magneto gap will adversely affect the
functioning of the ignition system, and too large a gap will also advance the ignition
timing. Always maintain the gap at 0.010 in.-0.012 in. The procedure for checking
and adjusting the gap is as follows-
(1) Remove the contact-breaker cover and rotate the engine slowly forwards until the
contacts of the contact-breaker are wide open.
(2) Insert the blade of the feeler gauge (attached to the magneto spanner) between the
contacts.
(3) If the feeler gauge just slides in without friction, the gap is correct and no
adjustment is needed. If the gauge is a slack fit or the contacts have to be sprung to
enable it to enter, adjust the gap as below.
(4) With the magneto spanner loosen the nut which secures the inner-contact screw
(see Fig. 45) and then adjust this screw by means of its hexagon head until the
correct gap is obtained between the fixed (outer) and adjustable (inner) contacts.
(5) Retighten the contact screw lock-nut and again c heck the gap. If correct, re place
the contact-breaker cover.

From the foregoing it will be observed that checking the contact-breaker gap does

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not necessitate complete removal of the contact-breaker from the magneto. The
same applies where cleaning is concerned.

FIG. 45. SHOWING DETAILS OF LUCAS ROTATING ARMATURE TYPE MAGNETO (1945-53)
In Fig. 39 is shown a view of the contact-breaker dismantled.

To Check Contact-breaker Gap (1954-7 Models). On 1954 500 c.c. and all
1955 and subsequent models it is advisable after the first 500 miles to remove the
moulded cover from the Lucas type S.R.-l rotating-magnet magneto and check the
gap between the contacts of the contact-breaker. It is subsequently sufficient to
check the gap at intervals of about 2,500 miles. Actual adjustment is seldom
needed. The correct contact-breaker gap is the same as for the rotating-armature
type magneto, namely 0.010 in.-0.012 in.
The correct procedure for checking the contact-breaker gap is as described for the
magneto on 1945-53 models, described in sub-paragraph (1) to (3) on page 75.
Should an adjustment of the contact-breaker gap be necessary, slacken the two
securing screws (see Fig. 46) holding the fixed contact plate and 9 move the plate as
required until the gap is correct. Having made the required adjustment, firmly
tighten the two securing-screws, again check the gap, and finally replace the moulded
cover. Tighten its three fixing-screws firmly.

Cleaning the Contact-breaker. The contact-breaker, especially the contacts

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themselves, must never be permitted to get dirty or oily, otherwise ignition trouble
will inevitably ensue, and the contacts will become burned and pitted. When
checking the gap of the contact-breaker, always inspect the contacts closely and, if
they need cleaning, do this before finally adjusting the gap.

FIG. 46. CONTACT-BREAKER END OF LUCAS ROTATING­MAGNET MAGNETO (1954 ONWARDS)

This magneto (not fitted to 1954 350 c.c. models) has automatic ignition- control
mechanism on the driving side.

If the contacts have a grey, frosted appearance, it can be reasonably assumed that
they are fairly healthy. Should they be only slightly discoloured, clean both contacts
with a cloth moistened with petrol. Where the contacts are pitted or blackened, they
must be thoroughly cleaned with a fine carborundum stone or, if one is not
available, very fine emery-cloth. Afterwards all metallic dust and dirt must be
completely removed with a petrol-moistened cloth.
When cleaning and dressing the contacts, it is essential to, remove the minimum
amount of contact metal necessary to ensure: (a) brightness of the contacts, (b)
parallelism of the contacts, (c) perfect smoothness and truth of contact faces.

To ensure this, remove the spring arm, or contact-breaker lever (see Figs. 45 and 46)

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carrying the moving contact, by withdrawing (1945-53) the fixing screw and spring
washer, or (1954 onwards) the nut securing the end of the contact-breaker sp ring.
When replacin g the sp ring a rm on th e rota ting-a rmatur e magne to (1945-53), be sure
to fit the small backing spring (see Fig. 45) correctly. The curved portion mus t fac e
outwards. Remove any rust from the spring.

To Renew Ignition-Control Cable (1945-53). As may be seen in Fig. 45
slackness in the cable for advancing and retarding the spark can be rectified by
means of the cable stop after pushing the rubber protector upwards and slackening
the lock-nut. If, however, the cable frays, breaks or stretches unduly, it is necessary
to renew the cable in the following manner.
Do not attempt to remove the cam itself from its housing. Remove the cable
casing at the magneto by unscrewing the hexagon nut at its base. Draw fully
upwards the control cable and the attached plunger. This will cause the nipple into
which the cable-end is soldered to rise above the top of the boss on the cam-cage
housing. Slip the nipple sideways out of the hole in the plunger and completely
detach the cable. Now thread the new cable through the casing and solder the nipple
on to its end. Then slip the nipple sideways into the hole in the plunger and screw
the casing home. Finally, make the necessary adjustment by means of the cable
stop.

Cleaning the Slip-ring (1945-53 Models). Misfiring and some difficult starting
are sometimes caused by moisture, oil, or dirt collecting on the slip-ring. About
every 2,5W-3,000 miles remove the h.t. pick-up (see Fig. 45) from the magneto and
thoroughly clean the track and flanges of the slip-ring. The best way of doing this is
to cover a pencil with a soft cloth and press this against the slip ring while slowly
rotating the engine.

The h.t. Pick-up (1945-53 Models). When cleaning the magneto slipring, also
wipe the pick-up moulding and polish it with a fine, dry, cloth. Inspect the
moulding for cracks and examine the carbon brush (see Fig. 45) and spring, but be
careful not to stretch the spring. If the carbon brush is badly worn, renew it.
Before replacing the h.t. pick-up on the magneto, see that the carbon brush moves
freely in its holder and beds down properly on the slip-ring. Good electrical contact
is important.

To Renew h.t. Cable (1945-53 Models). Always use 7 mm. rubber covered
ignition cable. Referring to Fig. 45, bare the end of the cable for about 1/4 in. and
thread the cable through the moulded terminal. Pass the wire through the bronze
washer and then bend back the cable strands as illustrated. Finally, screw the
moulded terminal into the magneto pick-up.

To Renew h.t. Cable (1954 Onwards). Where a Lucas rotating-magnet type SR-1

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magneto is fitted, 7 mm. rubber-covered ignition cable is also required for renewal
purposes. To connect to the magneto, first remove the moulded cover from the
contact-breaker side, and unscrew the pointed screw (see Fig. 46) from the back of
the cover. Pull out the old ignition cable and push the new cable right home. Then
secure the cable by tightening the pointed screw. Its point will penetrate the
insulation and ensure good electrical contact with the core of the cable.

Testing the h.t. Cable. If the engine is running well, obviously the cable is sound
but, if the engine refuses to start, it is desirable to ascertain whether the h.t. current is
reaching the plug end of the cable. Place the the steel blade of a wooden-handled
screwdriver in contact with the plug terminal and almost in contact with one of the
cylinder fins. Kick the engine over smartly and note whether a "fat" spark occurs. If
it does, the cable is sound,- but if it does not the cable or magneto is at fault.

To Re-tension Magneto Chain (1945-56 Models). About every 3,000 miles
remove the cover from the magneto chain-case and inspect the chain for tension.
Some stretching occurs, especially on a new chain, and where this is excessive it
may spoil the exact ignition-timing and accelerate wear of the chain and sprockets.
Press the magneto chain-run up and down (in its tautest position) midway between
the magneto and camshaft sprockets. If the tension is correct, the total deflection
should not exceed approximately 1/4 in. If it is appreciably more or less, re-tension
the chain as described below. Over-tensioning may damage the magneto.
(1) Loosen the nuts on both bolts (nut on rear bolt only, 1954-7) whi ch support and
secure the adjustable magneto-platform.
(2) Insert the blade of a screwdriver beneath the front (rear, 1954 onwards) end of
the magneto platform and rise it upwards until the correct chain tension is obtained.
(3) Tighten firmly both nuts on the magneto-platform securing bolts. On 1954
and later models tighten the single nut on the rear bolt.
(4) Again check the tension of the driving chain.
(5) Grease the chain if necessary (see page 58) and fit the cover to the chain-case.
Do not use jointing compound. Tighten the various cover securing-screws evenly.

Automatic Ignition-control Mechanism. The control mechanism on the driving
side of the Lucas type SR-1 rotating magnet magneto (1954 onwards) requires no
adjustment, but the mechanism should be greased (see page 59) when greasing the
magneto chain.

The Correct Magneto-timing. Incorrect magneto-timing can have a most

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detrimental effect on the engine, besides reducing its performance. A late timing
will result in a "woolly" engine and a hot and noisy exhaust, with considerable
overheating and inability to develop full power. An early timing, on the other hand,
may result in the engine being powerful on the larger throttle openings, but it will
have a nasty tendency to kickback when being started and it will "knock" readily
under slight provocation. Worst of all, the engine will be subjected to some fuel
detonation and stresses for which it is not designed.
Never attempt to improve on the maker's timing, which is such that the contact­breaker contacts begin to open with the piston 7/16 in. before T.D.C. (1/2 in. 1949-

57) on the compression stroke. Sometimes it is necessary for some reason to remove
the magneto or its driving chain. Where this is done, the magneto must be retimed.
For this purpose it is desirable to have available the following two items -
(a) A stout screwdriver, or an old-type tyre lever with the end turned up.
(b) A small rod or stout wheel spoke about 5 1/2 in. long.

1. Timing the Magneto-Preliminaries. Remove the covers from (a) the contact­breaker, (b) the off-side of the rocker-box, and (c) the magneto chain-case. Also
remove the plug. Check that the gap at the contactbreaker is correct (0.010 in.-

0.012 in.) as described on pages 75 and 76. It is also advisable to check that the
magneto chain is correctly tensioned. The contact-breaker gap must be correct, as
this affects the timing appreciably.
Loosen by several turns the nut which secures the magneto-driving sprocket to the
camshaft, but do not take the nut right off. Then, with the stout screwdriver or the
tyre lever referred to above, placed behind the sprocket, lever the latter off the taper
on the camshaft. Rotate the engine forwards slowly until the piston is at true T.D.C.
with both valves closed, as described below.

2. Finding the Exact Piston Position. Slip the 5 1/2 in. length of rod through
the hole for the sparking plug. Rotate the engine forwards slowly until it is felt that
the piston is exactly at the top of its stroke. In this position no movement is
imparted to the rod. Without moving the piston, mark the rod flush with the top face
of the sparking-plug hole. Remove the rod and scratch another mark 7/16 in. (1/2
in., 1949-57) above the first. Again insert the rod through the sparking-plug hole
and slowly turn the engine backwards by means of the rear wheel (with top gear
engaged) until the upper of the two marks on the rod is flush with the top of the
sparking-plug hole. 7/16 in. and 1/2 in. equal 36 deg. and 39 deg. respectively
before T.D.C.

3. Timing the Contact "Break." With the piston still at 7/16 in. or 1/2 in.

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before T.D.C., advance the ignition-control lever (all 1945-53, and 1954 350 c.c.
models with manual control) on the handlebars fully by pushing it outwards to its
maximum extent. Where automatic ignition-control is provided (on 1954 500 c.c.
and all 1955 and later models) turn (with the finger and thumb) to the maximum
extent possible the front plate of the automatic ignition-control mechanism. This is
its fully advanced position. Lock the control in this position by inserting a small
wooden wedge. Without moving the piston, rotate the sprocket secured to the
magneto armature-shaft (and the driving chain) anti-clockwise, viewed from the
driving side, until the contacts of the contact-breaker are just beginning to open.
To determine the exact moment of the "break," insert a thin cellophane slip
between the contacts and exert a gentle pull on the paper when the magneto sprocket
is being slowly turned.
When the exact position of the "break" has been found, secure the sprocket to the
camshaft, being most careful not to permit the camshaft and/or armature to move
while tightening the camshaft nut.
Finally check over the magneto timing again, verify the chain tension, grease the
chain (see page 58) if necessary, and replace the covers for the contact-breaker,
rocker-box and magneto chain-case. Before replacing the magneto chain-case cover
do not forget to remove the wooden wedge previously used to lock the automatic
ignition-control mechanism in the fully advanced position. Fit the sparking plug
and you should be "all set."

DIAGNOSING IGNITION FAULTS

Diagnosis is facilitated by noting the behaviour of the engine just before its
failure, the onset of which may be gradual or sudden, and partial or complete. A
complete failure is generally easier to diagnose than a partial one, because there
must be something radically wrong. When checking the ignition system, use the
following sequence-
(1) Test the h.t. lead at the sparking-plug end.
(2) If a "fat" spark occurs at the plug end of the lead, test the plug itself.
(3) If a weak spark, or no spark, occurs at the plug, inspect the sparking plug
carefully.
(4) Where the plug appears to be all right, examine the magneto contac t-breake r (see
pages 75-7).
(5) Should the contact-breaker be clean and correctly adjusted, remove the h.t. pick­up from the magneto and inspect the pick-up, carbon brush, and slip-ring (See page

78).
(6) If the cause of the trouble still eludes you, check the timing of the magneto (see
page 80).
(7) In the event of the magneto timing being dead right, reconsider the possibility

of a carburation defect or the more remote possibility o f a f aulty mag ne to condenser,

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insulation, or loss of magnetism. Also take into account the mechanical condition of
the engine. It is assumed that you have checked and if necessary adjusted the tappet
clearances.

TAPPET ADJUSTMENT

Check and, if necessary, rectify the tappet adjustment every 3,000 miles. It is

generally necessary to adjust both tappets after every
5,000 miles. The adjustment must always be checked
after decarbonizing the engine and grinding-in the
valves. The need for tappet adjustment more frequently
than about once every 5,000 miles is generally due to
some fault which should be investigate d. It is of vital
importance to keep the adjustment correct to prevent
damage to the valves and to maintain high engine
performance.

The Clearance. On 350 c.c, 500 c.c. models the

FIG. 47. TAPPET
ADJUSTMENT ON
350 c.c, 500 c.c. O.H.V.
ENGINES
(see also Fig. 48)

Detach the cover from the off-side of the rocker-box after removing the three

retaining nuts and fibre washers. This exposes the inlet and exhaust tappet
adjustment. As may be seen in Figs. 47 and 48, each push-rod has an adjustable head
A secured by a lo ck-nut B to the push-rod sleeve C*

correct tappet clearance is nil with both valves closed
and the engine cold (warm, not hot, on all 1953-7
models). A clearance of nil implies that the push-rods
are free to rotate without any appreciable up-and-down
play.

1. Compression Plate Omitte d (1949 onwards). Turn the engine (350c.c. or

500 c.c.) over slowly until the piston is at T.D.C. on the compression stroke, with
both valves closed. See that the exhaust-valve lifter is not preventing the exhaust
valve from seating fully. Then check the tappet clearance for both tappets (see
above). Referring to Fig. 47, if an adjustment of either or both tappets is required,
hold the push-rod sleeve C with one spanner, and with another loosen the lock-nut
B. Then screw the adjustable head A up or down until a tappet clearance of nil is
obtained.

Afterwards tighten the lock-nut (B) (without moving head (A) and again check

the clearance.

* Note that a new sleeve cannot be fitted to an existing light-alloy push- rod, the sleev e and th e rod being
simultaneously threaded (internally) for the adjustable head, during manufacture.

2. Compression Plate Fitted. On 1945-8 500 c.c. engines having a compression

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plate, to adjust the tappet clearance, first rotate the engine until the exhaust valve
lifts off its seat. Referring to Fig. 47, first slacken the lock-nut (B) on the exhaust
push-rod (C). Next rotate the engine until the inlet valve is lifted off its seat.
Loosen the lock-nut (B) on the inlet pushrod (C). Now screw the adjustable head
(A) of the exhaust push-rod up or down as required to obtain a clearance of nil.
Further rotate the engine until the exhaust valve is lifted off its seat. Now tighten
the lock-nut (B) on the exhaust push-rod. Afterwards screw up or down as required
the adjustable head (A) on the inlet push-rod (C) until tappet clearance is nil. Again
rotate the engine until the inlet valve is raised, and tighten the lock nut on the inlet
push-rod.

3. After Tappet Adjustment. Turn the engine over until both valves are closed.
Check that the push-rods are free to rotate without appreciable up-and-down
movement. Fit the cover to the off-side of the rocker-box and replace the three
retaining nuts. Make sure that the three fibre washers are also replaced beneath the
nuts. When tightening the nuts avoid using excessive pressure on the spanner. Such
pressure is quite unnecessary, because a rubber fillet is incorporated at the rocker­box cover joint. Moderate pressure with the spanner will suffice to prevent oil
leakage. Tighten the three nuts evenly.

DECARBONIZING AND VALVE GRINDING

The exact time at which the removal of carbon deposits becomes necessary
depends to some extent on (a) quality of the fuel used and (b) the driving conditions.
Under normal circumstances it is advisable to remove the cylinder head, decarbonize
and, if necessary, grind-in the valves when the performance declines. If the engine
develops a tendency to "knock" when accelerating quickly or hill-climbing, this
confirms that the time for decarbonizing is due.
Do not remove the cylinder barrel unless you have good reason to inspect the piston
and rings, and perhaps the bore of the cylinder. Remove the barrel, however, if any
stiffness of the piston occurs, or if loss of compression (not caused by bad valve
seating) develops. Decarbonizing and grinding-in the valves is quite simple if you
follow the correct procedure (Sections 1-23).

1. Remove Petrol Tank. It is necessary to remove the petrol tank before
detaching the rocker-box and cylinder head prior to decarbonizing, also when
undertaking any major engine overhaul work. To remove the tank, turn both petrol

taps to the "Off position. Disconnect the petrol pipe from both taps, using two

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spanner s ( h o l d t he t a p s when uns cr e w i n g the unio n n uts or cap nuts (1955-7).

FIG. 48. PREPARING FOR ROCKER-BOX REMOVAL

The petrol tank, the oil-feed pipe to the rocker-box, and the rocker box cover have been removed . The next
operation is to remove the engine-steady bracket connecting the rocker-box t o the frame top-tube, and then
remove the rocker-box securing bolts.

Then sever the loc king wires securing the four tank-fixing bolts (see Figs. 53-55).
Now unscrew the four fixing bolts and ease the tank clear of the frame.
NOTE: The makers advise removal of the dualseat on 1954 "springer" models
before attempting to remove the petrol tank. On 1953 "springer" models they
recommend removing the handlebars (secured by three Allen screws) and resting the
bars on the handlebar In- forward of the steering head adjuster-nut.

2. Remove Rocker-box (1945-57). After tank removal, the next step towards
cylinder-head removal is to take off the rocker-box and push-rods. First remove the
three nuts retaining the cover to the off-side of the rockerbox. Also remove the three
fibre washers beneath the nuts. Then take off the rocker-box end-cover as shown

in Fig. 48. Disconnect the upper union of the oil-feed pipe from the pump to the

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rocker-box. Now rotate the engine slowly until both inlet and exhaust valves are
closed. On 1945-53 500 c.c. and all later engines, detach the engine-steady bracket
(see Fig. 48) between the rocker-box and frame top-tube. To do this, remove th e
nuts and washers from the rocker-box bolt extensions and also the bolt from the
frame clip.
With a spanner, remove the seven bolts (nine, 1949-57) securing the rocker-box to
the cylinder head. Disconnect the exhaust valve-lifter cable. Grip the rocker-box,
tilt up its right-hand side and withdraw both pushrods. These should not be
interchanged, and for this reason should be marked or placed so that they can
subsequently be identified. Now carefully lift the rocker-box clear of the cylinder
head. On 1945-8 engines raise the front end of the rocker-box, so as to clear the
exhaust-valve assembly, and swing it round anti-clockwise to clear the frame tube.
The rocker-box may now be lifted clear of the inlet-valve assembly and removed
from the engine. Be careful not to lose the hardened-steel caps on the ends of the
valve stems (1945-8 engines). These caps are most important.

3. Remove Cylinder Head. Having removed the fuel tank and rockerbox as
previously described, unscrew the sparking plug.* Then proceed to remove, or
partially remove, the exhaust system. Before this can be done (1945-6 350 c.c.
engines) remove the right-hand side of the footrest rod. Remove the nut and washer
on the right-hand side of the footrest rod and partially withdraw the footrest rod
from the left-hand side. Now prise off the right-hand side footrest-arm.
To remove the exhaust system, first remove the nuts and washers which secure the
exhaust pipe and silencer to their stays. Then pull the exhaust pipe and silencer
away from the stays, and pull the pipe downwards from the port in the cylinder head.
Remove the Amal carburettor by unscrewing the venturi air-intake (1945-8
models) and the two nuts securing the carburettor flange to the cylinder head. The
carburettor may be allowed to rest on the saddle or on the platform above the
dynamo as shown in Fig. 51; it is not necessary to remove the throttle ana air slides
from the carburettor.
Next remove the four bolts which retain the cylinder head to the cylinder barrel. If
these are stiff, brush paraffin round their heads and allow to penetrate before again
using the spanner. Lift the cylinder head from the cylinder barrel and
simultaneously remove the push-rod cover tubes which come away with the cylinder
head.

* Should the sparking plug be difficult to unscrew, do not apply excessive force with the box spanner. Brush
some paraffin round the plug body and allow to soak prior to further use of the spanner.

4. To Remove Cylinder Barrel. Rotate the engine so that the piston is near

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B.D.C. Next remove the four nuts which secure the cylinder barrel to the crankcase,
and then gently draw the barrel off the piston. Steady the latter with one hand as the
barrel is withdrawn, and take great care not to allow the piston to fall sharply against
the connecting rod. After removing the cylinder barrel, cover the mouth of the
crankcase with a clean rag.

5. Piston Removal. To remove the fully-floating gudgeon-pin, it is only
necessary to extract one circlip with the snipe-nosed pliers provided in the tool kit.
Push the gudgeon-pin out from the opposite side and remove the piston. The
gudgeon-pin is an easy sliding fit in the piston bosses and the small-end bush, If the
piston is not of the split-skirt type, scratch an "F" on the inside to indicate which is
the front.

Condition of Piston. A piston will run well for very many thousands of miles; but
eventually loss of compression and/or piston slap occurs due to wear of the piston,
rings, and cylinder bore, especially the last-mentioned. Examine the cylinder bore
occasionally for longitudinal scores and circumferential ridges. Also inspect the
piston for blackening of the skirt, scores, smearing, and other possible damage,
particularly near the ring lands. The normal front to rear clearance for standard size
1953 and later pistons (new) is 0.001 in. plus or minus 0.0005 in.

Cylinder Rebores. After a very considerable mileage (when wear at the top of the
bore reaches 0.008 in.) it is usually essential to have a rebore and fit an oversize
piston and rings to restore the compression and performance of the engine to
normal. The makers provide for rebores 0.020 in. and 0.040 oversize, and can
supply 0.020 in. and 0.040 in. oversize pistons and rings to suit. Running-in is, of
course, necessary after a rebore.

6. Removing Piston Rings. The piston rings should not be disturbed more
frequently than once every alternate decarbonizing, provided that engine
compression remains good. The rings can be removed by "peeling off with a small
knife, but it is preferable to remove them with the aid of three strips of thin sheet­metal (about 1/4 in. wide) inserted beneath each ring as shown in Fig. 49. The
rings, being made of cast iron, cannot safely be sprung out wider than the piston­crown diameter. If the rings are stuck with carbon, apply some paraffin. If this fails,
use a proprietary ring removal tool.

7. Examining Piston Rings. Inspect the two compression rings and the scraper
ring very carefully. To ensure good engine compression the piston rings must have
good springiness, be free, but not slack in their grooves, have a polished surface all
round, and have their gaps equally spaced and of the correct size.

If inspection reveals that the ring surfaces are bright all round, they are obviously

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making good circumferential contact with the cylinder bore and can be regarded as
serviceable. If, on the other hand, the surfaces are discoloured or scorched at some
points, contact is poor and it is desirable to reject the rings and fit new ones. The
same applies where the rings are vertically slack in their grooves.
Clean the rings thoroughly on their inside faces, also the ends of the rings, and the
slots in the scraper ring (see Fig. 49). Piston rings are made to very precise
dimensions, and it is not generally practicable to fit oversize rings unless the piston
is renewed also. Always fit genuine A.J.S. rings which are dimensionally correct.
To reduce cylinder-bore wear, a chromium­plated top compression ring is fitted to 1953
and later engines.

8. Piston Ring Dimensions. The widths
of the compression rings and the slotted
scraper-ring on all engines are 1/16 in. and
1/8 in. respectively. The normal ring gap is

0.006 in. to 0.008 in. and rings should be
renewed when the gap exceeds 0.030 in. The
normal clearance of each ring in its groove is

0.003 in. (0.002 in. on 1950-7 engines).
After a considerable mileage, or if loss of
compression occurs with the valves in good
condition, check the gap of each piston ring.
The best method of checking the gap is to
push the ring squarely into the bore of the
cylinder barrel with the aid of the piston and
then check the gap between the ends of the ring with a feeler gauge. If the gap
proves excessive, fit new A.J.S. rings (already "gapped"); If the gap is insufficient,
remove some metal from one end of the ring to increase the gap to 0.006 in.

FIG.49. THE SAFEST

METHOD OF REMOVING AND
FITTING PISTON RINGS

.

9. To Remove Valves (1945-8). A valve-spring compressor is not essential. Lay
the removed cylinder head on the bench or table and rest each valve head in turn on
a small wooden block. Then compress the duplex valve-springs by exerting pressure
on the outer collar until the split collet can be removed from the valve stem. It may
be necessary to tap each collar sharply to free the split collet, as the latter is a taper
fit in the collar. On the 500 c.c. engine the inlet and exhaust valves are of identical
size, unlike those on the 350 c.c. engine, but valves must not be interchanged.

To Remove Valves (1949-51). Hairpin springs are fitted to all 1949 and later 350

b

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c.c. and 500 c.c. O.H.V. single-cylinder engines, and to remove the valves it is
necessary to use the special A.J.S. valve-spring compressor illustrated in Fig. 50.
This tool is not included in the tool kit, but is obtainable for a small sum from an
A.J.S. dealer or the manufacturers.

FIG. 50. VALVE-SPRING COMPRESSOR (PART No. 014605) FOR
ENGINES WITH HAIRSPRING VALVE-SPRINGS (1949-51)

KEY TO FIG. 50

1. Inlet port. 5. Long (operating) bolts.

2. Hole for screw controlling oil 6. Compressor body.

feed to the Inlet-valve stem. 7. Valve-spring collar.

3. Oil duct from rocker-

valve guide. 9. Hole for inlet-valve guid e

4. Compressor-attachment bolts

(Part No. 010795).

After removing the cylinder head (see page 85) attach the flat ends of the A.J.S.
valve spring compressor to the cylinder head by means of the two short attachment
bolts as shown in Fig. 50. Then compress the hairpin valve-springs provided for
each valve by screwing in evenly the two long bolts of the compressor. The
countersunk depressions on the valve spring top-cap engage the reduced-diameter
ends of the two long bolts.

ox to 8. Hairpin valve-springs.

When the hairpin valve springs are sufficiently compressed, withdraw the split

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collet from the valve stem which has no detachable valve-stem end cap. Then
withdraw the valve from the combustion chamber. When the valve has been
withdrawn, remove the valve-spring compressor from the cylinder head by
slackening each of the two long bolts evenly and gradually until these two bolts are
clear of the valve-spring top cap. Afterwards remove the complete hairpin valve­spring assembly. Deal with each valve and spring assembly in the manner described
above. Remember that the valves are not interchangeable. It is advisable to put
each valve assembly into separate boxes after dismantling to avoid any possibility of
error when reassembling.

To Remove Valves (1952 Onwards). On all 1952 and later engines a modified
and improved hairpin valve-spring assembly renders it unnecessary to employ a
valve-spring compressor to remove the valves, though a compressor (see Fig. 52) is
needed for replacing them. To remove each hairpin valve-spring, insert a finger in
the spring coil and pull the coil sharply upward. You can then take off the valve­spring collar and split collet, and withdraw the valve. If the tapered split collet is
stuck, deliver a sharp tap on the collar to free it.
Note that the modified seat for the valve-spring has a raised impression on its
under side; this registers with a hole drilled in the valve-guide boss to ensure proper
location. Note also that, as hitherto, the valves are not interchangeable and must be
identified for correct replacement (see notes on page 91).

10. Removing Carbon Deposits. The best tool to use for scraping off the carbon
deposits is an old (blunted) screwdriver, or a proprietary scraper (obtainable from
most accessory dealers). For cleaning piston-ring grooves a suitable scraper can be
made up by fitting a handle to a piece of broken piston-ring, or better still a
proprietary tool can be obtained for the purpose. It is worth while decarbonizing
thoroughly, as carbon deposits form less rapidly on smooth surfaces. Where
deposits are found to be very hard, the application of paraffin will facilitate their
removal.
If the cylinder barrel has not been removed, scrape off all carbon from the piston
crown, but on no account use any abrasive. Should this get between the piston and
cylinder (as it probably would) your A.J.S. would rapidly go into a decline! Be very
careful not to make any deep scratch marks on the comparatively soft surface of the
light-alloy piston. Scrape off all carbon from the inside of the combustion chamber.
Do not forget to chip off and completely remove all carbon from the valve ports,*
the vicinity of the valves, the valve heads and the sparking-plug hole. It is
permissible to use some fine emery-cloth to polish up the combustion chamber
surface, but if this is done the cylinder head must afterwards be very thoroughly
cleaned and all trace of abrasive particles removed. Use a rag damped with paraffin.
Do not touch the cylinder bore.

* If close inspection reveals any roughness of the metal surfaces inside the inlet or exhaust port, it is beneficial
to smooth out such irregularities with a curved rifier.

If the cylinder barrel and piston have been removed, it may be advisable to scrape

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carbon off the inside of the piston but, unless the deposits are thick, this should not
be done. Remove all carbon from the piston crown, but do not touch the skirt. Any
attempt to scrape the piston skirt may have disastrous results. The piston-ring
grooves, however, need attention. Clean these up thoroughly, but be very careful
not to damage the actual metal comprising the sides of the grooves. Make sure that
the holes in the groove for the scraper ring (see Fig. 49) are unobstructed.

FIG. 51. SCRAPING THE CARBON OFF THE PISTON WITH A
BLUNT SCREWDRIVER

The piston should first be positioned at T.D.C. When chipping off the carbo n, hold the screwd river in th e
manner shown. Note the carburettor laid beside the electric born for convenience.

The cleaning of piston rings is referred to on page 87. After decarbonizing is
complete, clean all parts thoroughly with suitable clean rags and paraffin.

11. Grinding-in the Valves. Although the engine manufacturers recommend that
the valves be inspected every time the engine is decarbonized, it should be
understood that excessive valve grinding is not advisable as this is liable to cause the
valves to become "pocketed," with a resultant loss of engine efficiency. If the valves
are seating perfectly, leave them alone; otherwise grind in both valves.
After removing the valves for grinding-in, clean both valve heads thoroughly and
polish the valve stems with some worn fine emery-cloth, using an up-and-down
motion with the emery-cloth held between the forefinger and thumb. Then proceed
to grind-in each valve as described below, using a good grinding paste such as
Richford's (tins contain two grades, coarse and fine).

To grind-in a valve, first smear the bevelled face of the valve with a thin layer of

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grinding paste. If the valve face and seat are only slightly pitted, it should be
sufficient to use a,6ne grade of paste only. Serious pitting may necessitate the
preliminary application of a coarse grade and, if the pitting is very severe, it may be
necessary to have the valve seats refaced at a garage with a cutter having a cutting
angle of 45 degrees.
Insert the valve in its seat and oscillate the valve about a quarter of a turn
backwards and forwards by means of a suitable valve holder. Maintain a slight
pressure between the valve and its seat and lift the valve occasionally (when the
abrasive ceases to bite) and turn it to a new position. Continue to grind-in the valve
until a continuous matt ring is present on both the valve seat and the valve.
Generally one application of grinding paste is sufficient for the inlet valve, but the
exhaust valve may require several applications to obtain good results. The part
number of the A.J.S. valve holder is 11520A for 1945-50 engines, or 017482 for
1951 and all subsequent engines. The later type valve-holder (a suction-rubber
type) will, however, suit the valve stems of all engines.

12. After Grinding-in. See that every trace of grinding paste is eradicated by
cleaning the valves and the two seats with petrol and a clean rag. To ensure that
the valve guides are free from damaging abrasive, it is advisable to draw a piece of
clean rag through both guides.

13. To Check Valve Spring Length (1945-8). After much use the hardpressed
valve springs may weaken under the influence of heat, and thereby spoil the quick
and positive action of the valves, which is so vital to high engine efficiency. The
condition of the valve springs is reflected in their free length, which should be
checked very occasionally with a small rule. On 1945-7 350 c.c, and 500 c.c.
O.H.V.engines,the free length of inner and outer valve springs is 1 13/16 in. and 2
1/16 in respectively.* Renew immediately any valve springs whose free length is
found to be more than about 7/32 in. below the free-length dimensions quoted
above.

14. To Replace Valves (1945-8). Clean the insides of both valve guides,
smear some engine oil on the valve stems. Then fit the inlet and exhaust
valves in their respective guides. On the 350 c.c. engine the inlet valve can
immediately be recognized, as it has a head of larger diameter than the exhaust
valve. On the 500 c.c. engine, however, the dimensions of both valves are identical,
though the material differs. In this case, before fitting the valves, note the markings
"IN" and "EX" on top of the inlet and exhaustvalve stems respectively, above the
grooves for the split collets.

* On 1948 engines the free length of the inner and outer valve springs is 2 in. and 2 13/64. in. respectively.
1949-57 engines have hairpin valve-springs.

Rest each valve head in turn on a small wooden block, and fit the duplex valve

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springs and collars. Compress the valve springs and then fit the split collet. A
distance sleeve must be fitted next to the cylinder head under the lower collar for the
exhaust-valve springs, but this does not apply to the inlet valve. Make quite sure
that both split collets are properly located. The two grooves machined in the bore of
each split collet must both register with the corresponding rings on the valve stem,
otherwise damage may result. Finally replace the hardened caps on the ends of the
valve stems. Under no circumstances must these caps be omitted. Failure to replace
them will cause wear and possibly actual damage through fouling of the oil lug on
the rocker-box by the tappet adjuster-head.

To Replace Valves (1949-51). With engines fitted with hairpin-type springs,
clean both valve-guide bores with a clean rag and smear some engine oil on each
valve stem. Next replace both valves in their guides. Note the remarks (see page

91) regarding their correct identification. Place some packing beneath each valve
head with the cylinder head resting upright on the bench.
Replace each hairpin valve-spring assembly. See that the dowel pin on the valve­spring block (to which the prong ends of the hairpin valvesprings are attached) beds
into the hole in the valve-guide boss.
If for some reason the valve springs are detached from their fixing block, It is
essential to make sure that on assembly the spring with the narrow spaced prongs is
entered into the block from the chamfered end.
Compress the hairpin valve-springs by fitting the A.J.S. spring compressor tool as
shown in Fig. 50 and then tightening the two long bolts evenly. Now replace each
split collet on the valve stem. Be sure that it is correctly located. The split collet
has two grooves machined in the bore and these must register with the two rings on
the valve stem. Damage will probably be caused if the split collet is fitted so that
only one groove engages one valve-stem ring. Finally remove the valve-spring
compressor by loosening the two long bolts and lifting it off the cylinder head.

To Replace Valves (1952 Onwards). Thoroughly clean the bores of both valve
guides and smear a film of engine oil on the stems of the valves. Replace the latter
in their correct guides. On 350 c.c. engines wrong replacement is impossible, but on
500 c.c. engines the inlet and exhaust valves must be identified (see page 91).
Insert suitable packing beneath each valve head and place the cylinder head in its
normal position on the bench. Then fit each hairpin valve-spring as described
below.
Fit the valve-spring top collar and the split collet.* Then position the hairpin
valve-springs and proceed to compress each spring with the special A.J.S. valve­spring compressor shown in Fig. 52.

* Make quite sure that the two machined grooves on the bore of the split
collet register with the corresponding rings on the va lve stem.

The standard tool kit does not include this compressor, but it can be obtained from

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the makers or an A.J.S. dealer. To use the compressor, apply the upper end of the
valve-spring to the groove in the top cap; insert a short rod (e.g. a rocker-box
securing bolt) through the holes in the com pressor (and the val ve-spring coils) and
pull upward and outward until the ends of the spring prong can be rested on the
scat. Then with the fingers, press down.

FIG. 52. VALVE-SPRING COMPRESSOR (PART No. 018276) FOR
ENGINES WITH HAIRPIN VALVE-SPRINGS (1952 ONWARDS)

KEY TO FIG. 52

1. Split collet. 6. Oil duct from rocker-box to inlet-valve

2. Valve-spring collar. guide.

3. Valve-spring collar. 7. Screw controlling oil feed to inlet-valve

4. Rocker-box bolt. stem.

5. Valve-spring compressor.

Remove the rod (or rocker-box bolt) as soon as the compressor lies against the
cylinder head, but maintain finger pressure until you have removed the rod (or bolt)
and the compressor tool. Finally push the spring down until it locates properly. Its
prong ends must lie flat on the seat.

15. Fitting Piston Rings. If these have been removed, fit them in their grooves,

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which should first be oiled. The safest method of fitting the piston rings is to use
three strips of thin sheet-metal, as illustrated in Fig. 49. Fit the (bottom) scraper ring
first, and then the two compression rings. Space the ring gaps evenly, that is, at 120
degrees to each other. It is assumed that the ring gaps are within the permissible
limits (see page 87). If new rings are fitted, these are correctly "gapped" by the
makers and are ready for immediate use.
On 1951-2 500 c.c. and all subsequent engines the top compression ring is
chromium plated and one edge is marked Top. See that this ring is replaced
accordingly. Note that after a considerable mileage the word TOP may become
unreadable, but for a very considerable period the correct assembly position for the
chromium-plated ring can be determined by the extra brightness of the edge which
makes contact with the cylinder bore. The bright edge must be at the bottom. When
eventually the ring becomes bright over its full width (indicating full contact with
the bore), it is permissible to replace the top compression ring either way round.

16. Replacing Piston. It is assumed that all parts are thoroughly clean and that the
piston rings have been refitted. Smear some engine oil on the gudgeon-pin and then
offer up the piston to the small-end of the connectingrod. The piston must be
replaced in exactly the same position as before. If it is of the split-skirt type, the
split itself must face to the front of the machine. This is essential.
Next insert the gudgeon-pin from the side from which the circlip has been
removed. Centralize the gudgeon-pin, and with the small snipe-nose pliers in the
tool kit replace the circlip using a rotary movement to ensure that it beds snugly into
its groove. Perfect fitting of the circlip is essential to prevent damage. If the
Condition of the old circlip is suspect, renew the circlip immediately.

17. To Replace Cylinder Barrel. A new washer must be fitted to the cylinder
base*, and its cylinder barrel side should be coated with liquid jointing-compound.
Make sure that none of the compound chokes any of the oil holes and that the holes
register properly. Now sm ear some engine oi l on the piston and cyl inder bore, and
then turn the engine so that the piston is at or near B.D.C. Verify that the piston-ring
gaps are spaced at 120 degrees and remove the rag from the mouth of the crankcase.
Ease the cylinder barrel carefully over the piston-compressing each ring as it
enters the bore mouth, to enable the barrel to slide over the piston without friction.
Finally replace the four cylinder-barrel retaining nuts. Tighten the four nuts, first
finger-tight, and then firmly in a diagonal order, turning each nut about one-quarter
of a turn at a time.

* On a 1945-8 500 c.c. engine with a co mpressio n p late, a p ap er wash er sh ou ld be fitted on each sid e o f it.

18. Fit the Cylinder Head. Wipe the bottom face of the cylinder head and the

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top edge of the cylinder barrel absolutely clean. Then fit the pushrod cover tubes to
the cylinder head. See that the rubber gaskets are in good condition, and fitted
between the top ends of the cover tubes and cylinder head. If the push-rod cover
tubes were pulled away from the cylinder head during stripping down, it would
probably be found that the rubber gaskets have remained located in the cylinder
head. Also check that the metal washers are interposed between the top edges of the
rubber gaskets and the recesses in the cylinder head (see Section 19).
Fit the cylinder head gasket on the top edge of the cylinder barrel. If the gasket is
not in perfect condition, renew it. Whether you fit a new gasket or use the old one,
it is advisable to anneal it just before placing it on the cylinder barrel. To anneal the
gasket, heat it to a "blood red" colour and plunge into cold clean water.
Place the two rubber glands round the inlet and exhaust tappet guides. Then
replace the cylinder head on the barrel, complete with push-rod cover tubes, and fit
the four cylinder head retaining bolts. Each bolt must be fitted with a plain steel­washer. Tighten each bolt a few turns and then gradually tighten all four, using a
diagonal sequence to ensure an even pressure being exerted on the cylinder head.

19. Fit Correct Washers to Push-rod Cover Tube. It is essential that the
correct metal washers are fitted to each push-rod cover tube. A compression plate
is not fitted to 1945-8 350 c.c. and all 1949-57 engines; on these, two metal washers
(not interchangeable) must be fitted to each push-rod covertube. Fit one of these
metal washers below the top rubber-gasket, and the other one above the top rubber­gasket.
A 1/8 in. thick compression plate is fitted to all 1945-8 500 c.c. engines, and on
these two metal washers must also be fitted to each push-rod cover tube. Fit one
metal washer (Part No. 01 1087) 3/64 in. thick below the top rubber-gasket, and a
second metal washer (Part No. 014603) 1/8 in. thick above the top rubber-gasket.
Should you for any purpose desire to increase the compression ratio on a 1945-8
500 c.c. engine from 6.00 : 1 to 7.24 : 1 by removing the 1/8 in. thick compression
plate, you must substitute a 3/64 in. thick washer for the 1/8 in. thick washer fitted
above the top rubber-gasket on each push-rod cover tube.

20. Fit the Rocker-box (1945-8). Wipe the lower face of the box and the upper
face of the cylinder head absolutely clean. Verify that the hardened-steel caps are
fitted to the ends of the inlet and exhaust-valve stems. Then rotate the, engine so
that the piston is at or near T.D.C. on the compression stroke, with both tappets right
down.

Place the special-composition washer on the cylinder-head face for the rocker-box,

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but before doing this inspect it carefully. Renew this washer if there is the slightest
sign of damage. When fitting the composition washer make sure that its small lip is
concentric with the small hole in the cylinder head through which oil is fed to the
stem of the inlet valve.
Now place the rear end of the rocker-box over the inlet-valve assembly and swing
it clockwise over the exhaust-valve assembly until it is in the normal position. Next
raise the offside of the rocker-box slightly and insert the two push-rods down the
push-rod covers, being careful not to interchange the inlet and exhaust rods. Make
certain that the push-rod ends engage the tops of the flat-base tappets and the
overhead rocker-arm ends.
Push the rocker-box right home and fit the seven rocker-box retaining bolts and
plain steel-washers. See that the bolt having a short head is fitted in the centre,
right-hand position. On the 500 c.c. engine (Model 18) be careful to replace the bolt
with the threaded extension (for the engine steady-stay) in its correct position.
Tighten all seven bolts lightly and then, using a diagonal sequence starting near the
centre, firmly tighten them all, turning each nut a little at a time.
Connect the engine steady-stay (500 c.c. only) to the rocker-box bolt with
threaded extension, and fit the washer and nut. Bolt the other end of the steady to
the clip on the frame down-tube. Rotate the engine a few turns to enable all parts to
bed home. Then with the appropriate spanner, check that all rocker-box retaining
bolts are firmly tightened. Having done this, reconnect the exhaust-valve lifter
cable, and check the tappet clearances and adjust, if necessary (see page 82).

Fit the Rocker-box (1949 Onwards). Clean the lower face of the rockerbox and
the upper face of the cylinder head. Next slowly turn the engine until the piston is at
T.D.C. with both tappets right down. Inspect the cylinder-head composition washer
(renew if not perfect), and lay the washer on the cylinder head.
Position the rocker-box and then raise slightly the off-side of the box to permit the
two long push-rods to be inserted in their original positions. Now fit the nine
rocker-box securing bolts. Note that the bolt with the short head goes in the centre
right-hand position, while on 1949-53 500 c.c. and all later engines the bolts having
the threaded extensions go one on each side of the central short-headed bolt.
Tighten in a diagonal order and evenly all nine rocker-box securing bolts.
On 1949-53 500 c.c. and all later engines fit the engine steady-stay and then rotate
the engine a few times so as to be sure that the various parts bed right down. Now
reconnect the exhaust-valve lifter control and check the tappet clearances (see page

82).

21. Fit Oil Pipe and Rocker-box Cover. Reconnect the oil-fee d pipe from the
pump to the rocker-box. Use two spanners when tightening the upper union, to
prevent the union (screwed into the rocker-box) from turning.

Fit a new rubber fillet to the rocker-box side cover if examination of the fillet

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shows deterioration. Then fit the rocker-box side cover to the rocker-box, and
replace the three fibre washers and securing nuts. Tighten these nuts evenly, but not
too tightly. The provision of a rubber fillet renders excessive tightening quite
unnecessary.

FIG. 53. PETROL-TANK MOUNTING (1945-8)
The fixing bolt at the rear of the tank on the near-side has a hexagon head, and a
metal washer is used instead of a thin rubber p ad.

22. Final Engine Assembly. Final reassembly, after decarbonizing, is completed
by replacing the Amal carburettor, the sparking plug, exhaust system, and footrests
(1945-6). When fitting the Amal carburettor, it is important to obtain an absolutely
air-tight joint at the attachment flange.
Renew the washer if not perfect, also the copper washer for the sparking plug. Sm ea r
some graphite paste on the plug threads.

23. Replace Petrol Tank (1945-8). The pet rol ta nk is se cured b y its four fixing­bolts and a number of rubber pads and metal washers. Details of a fixing-bolt