Ajs 1933 1934 AJS Pitmans Book of the Ajs 1933 1934 AJS Pitmans Book of the

THE MOTOR-CYCLIST'S LIBRARY

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The BOOK of the

A.J.S.

W. C. HAYCRAFT

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THE MOTOR-CYCLIST'S LIBRARY

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THE

BOOK OF THE A.J.S.

A COMPLETE GUIDE FOR OWNERS

AND PROSPECTIVE PURCHASERS

OF A.J.S. MOTOR-CYCLES

BY

W. C. HAYCRAFT

DEALING WITH EVERY PHASE OF THE SUBJECT,
INCLUDING CHAPTERS ON DRIVING, TOURING,

PRELIMINARIES, I.C. ENGINE THEORY, TRACING

FAULTS, AND OVERHAULING

THIRD EDITION

LONDON

SIR ISAAC

PITMAN &

1933

SONS,

LTD.

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PREFACE

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WORLD-WIDE trade depression during 1931 has resulted in
several firms being taken over by new proprietors. On going to
Press with the Third Edition of this little handbook, the author
finds that the firm of Messrs. A. J. Stevens & Co., Ltd., no longer
exists, the whole of their goodwill and equipment having been
taken over by the well-known Matchless concern (Messrs. Colliers,

Ltd., of Plumstead). It is the intention of this firm to carry on
the manufacture of A.J.S. machines of exactly the same high
quality as have issued from the Wolverhampton concern. During
the 1932 season a limited programme is available, comprising
four overhead-valve and two side-valve models. Series "T," as
these machines are known, are dealt with in the present edition.
They are rather similar but improved versions of the 1931 "S"
series. It will be observed that series "T" includes no "cam­shaft" models, but speedmen and racing enthusiasts will be
delighted to learn that the famous and successful "camshaft"
models, on one of which Denly attained a speed of 118·98 m.p.h.
at Arpagon in France, will be reintroduced as soon as the new

firm has completed its reorganization of the A.J.S. manufacturing
equipment now transported bodily to Plumstead. A.J.S. Big
Twins will also be revived.

Series " T" will be continued practically unaltered for 1933,
and hence this edition will remain quite up to date until 1934.
The author has retained many useful notes for the benefit of
owners of 1929-31 models, but he does not propose to deal at any
length with the "camshafts," as these machines are primarily
designed for racing and competition purposes and thus outside
the intended sphere of this handbook.

It is only fair to conclude by mentioning that the author has
no present or past connection with Messrs. A.J.S. Motor Cycles
(Colliers), Ltd., to whom he is greatly indebted for supplying
information and photographs.

As hitherto, the author's advice is at the disposal of readers who

care to write to him c/o the Publishers.

W. C. H.

CHAP

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11.

.

I.

PREFACE

THE

A.J.S. SERIES

VARIOUS

PRELIMINARIES

CONTENTS

PAGE

V

1

28

III.

DRIVING

IV.

RUNNING COSTS AND TOURING

V.

HOW

VI.

FAULTS : THEIR LOCATION AND REMEDY

VII.

OVERHAULING

INDEX

HINTS AND TIPS

THE ENGINE WORKS

3

61

67

99

109

155

6

THE BOOK OF THE A.J.S.

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CHAPTER I

THE A.J.S. SERIES

Series “T.” The 1932 programme, which may be regarded as a

temporary measure prior to the introduction of a more compre­hensive range, including overhead camshaft machines early in
1933, comprises six machines, all of which have inclined engines.
Of these, four are of the overhead-valve type and two of the side­valve type. The overhead-valve models, all of which enable a
rider to enjoy a 70 m.p.h. “blind” if he so desires and have extra­ordinary acceleration, are Models T6, TB6, T8, TB8, and their

respective prices are, excluding electric lighting, £50, £40, £55,
£47. Models T6, T8 have twin-port engines and four-speed gear­boxes, while Models TB6, TB8 are “big port” (single-port)
models, and have Sturmey-Archer three-speed countershaft gear­boxes of special design. The two side-valve models are Models
T5, T9, priced at £38 10s. and £49 respectively. These two
machines are fast, and Model T9 is notable for the fact that
it has a detachable aluminium alloy cylinder head. Below the

principal characteristics of the 1932 range are given, the modifi-

fications for 1933 being dealt with on page 26.

SERIES “T” (1932-33) AT A GLANCE

c.c.

Stroke (m.m.)

Bore and.

Valves

Lubrication

Gear Ratios

Tyres

Model

349

T6 .

TB6*.
T8 .
TBS .
T5* .
T9 .

* These models weigh under 224 lb. and are thus taxed at 30s. p.a In the case

of model TB6 this weight is exclusive of the weight of the tool kit (see page 29).

349
498
498
349
498

74 X 81
74 X 81
84 x 90
84 x 90
74 x 81
84 x 90

O.H.V.
O.H.V.
O.H.V.
O.H.V.

S.V.
S.V.

Mech.
Mech.
Mech.
Mech.
Mech.
Mech.

1

5·8, 7, 12·6, 17·4
5·25, 8·12, 14·45

4·81, 5·8. 10·4, 14·4

5·03, 7·38, 13·43

5·8, 9, 16

4·81, 7·06, 12·85

26 x 3·25

25 x 3
26 x 3·25
26 x 3·25

25 x 3
26 x 3·25

2

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Tank-mounted Instrument Panels. Provision is made on all

A.J.S. machines, except Models T5 and TB6, for the fitting of
instrument panels on top of the petrol tank. These two models
where electric lighting is specified are fitted with the Lucas

“Maglita” lighting set, the extra price for which is £5. In this
instance the lighting switch is incorporated in the headlamp, and
if a speedometer is fitted it is mounted on the petrol tank itself.
On all other models the lighting set specified is the Lucas
"Magdyno," and the cost of fitting this (£9 10s.) includes the
instrument panel shown in Fig. 1, complete with speedometer,
ammeter clock, main switch, and concealed lighting switch.

FIG. 1. SHOWING THE NEAT MOUNTING FOR THE INSTRUMENTS

THE BOOK OF THE A.J.S.

SPECIAL A.J.S. FEATURES

AND ELECTRIC LIGHTING SWITCHES (SEE PAGE 26) .

Without the panel the extra charge for Lucas “Magdyno”
lighting is £5 10s. If preferred, instead of the standard finish for

the petrol tank (which holds 2 gal. except on Models T5, TB6),

a black and chromium finish may be specified for £1 extra. The
speedometer, it will be observed, is placed well forward so it may
be read easily and safely while travelling fast.

Adjustable Saddle., A really excellent feature on heavyweight

A.J.S. machines is the manner of mounting the saddle to make
adequate allowance for the variations in physical stature of
different riders. As may be seen in Pig. 2, in the case of Models
T6, T8, TB8, and T9, the saddle undercarriage at the front end is
provided with a bolt which may be inserted in either of three
holes in a lug on the top tube, and the rear end of the under­carriage is slotted to allow of the saddle being moved backwards
or forwards. As the illustration shows, the bottom of the coil
spring is permanently attached to the frame.

“Clean” Handlebars. Considerable attention has recently

been paid to cleaning up the handlebars. As may be observed
by a glance at Fig. 25, the arrangement is now not only

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exceptionally tidy, but the various levers and controls are situated
so as to fall easily to the hands. Their mountings are also made
integral with the bars, so that the possibility of vibration loosening

them is very remote.

FIG. 2. THE ADJUSTABLE SADDLE

Detachable Rear Carrier. Many riders who find a carrier

sometimes invaluable, but who declare that this fitment detracts

3

FIG. 3. THE DETACHABLE CARRIER

from the appearance of a sports model, are catered for by the

designers of the A.J.S. For an extra charge of 12s. 6d. the carrier

shown in Fig. 3 may be specified. Once fitted, its instant removal

requires only the taking off of four nuts and bolts, leaving the

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rear guard absolutely clear. The carrier itself is constructed of
steel tube, oxy-acetylene welded. It is standard on T6, T8, T9.

Quickly Detachable Rear Wheels. Punctures are rare nowadays,

but such things do occur when tyre treads begin to show wear.
It is then that a quickly removable rear wheel is an absolute boon
to the rider. To facilitate removal of the wheel the mudguard on
Models T6, T8, T9 is hinged, as shown in Fig. 4. This, in con-

junction with the special method of securing the rear wheel,

THE BOOK OF THE A.J.S.

FIG. 4. SHOWING HOW READILY

THE REAR, WHEEL MAY BE

renders removal of the latter an extraordinarily simple operation
devoid of any “snags.” No interference with wheel alinement,
brake adjustment, or transmission is involved. All the rider has
to do is to remove three sleeve bolts, a centre pin and a distance
piece. It would be difficult to imagine a more simple yet abso­lutely efficient system.

Front Brake Operation. On all models except Model T5 the

operating cable of the front brake passes down the front fork
blade. It is thus completely enclosed but for the small portion
protruding close to the operating lever to which it is attached.

REMOVED

FIG. 5. HOW THE CABLE TO THE

FRONT BRAKE ANCHOR PLATE

LEVER IS LED FROM THE

HANDLEBARS

Adjustment for the Bowden cable is provided af the fop of the

forks.

Four-speed Gear-boxes. Four-speed gear-boxes are fitted as

standard on Models T6, T8, 33/2, but may also be specified for

30s. on Models TB8 and T9. The ratios have been carefully

chosen so as to provide a first-class, all-round performance.
Acceleration and hill climbing capacity are greatly improved by
the inclusion of this extra speed.

Transmission Shock-absorber. An efficient shock-absorber, de-

tails of which are shown in Fig. 6, is fitted to the engine shaft of

FIG. 7. PRIMARY CHAIN CASE

all models. It provides a more even torque and damps out all
transmission shocks, thus imparting a sweeter top gear perform­ance when travelling at low speeds.

Totally Enclosed Primary Drive. Every 1932 A.J.S. has the

entire front chain, and also the clutch, enclosed in an oil-tight
chain case (Fig. 7). The chain thus requires only periodical
attention in order to maintain the oil level shown. An inspection
disc at the base of the case constitutes an oil level indicator.

THE A.J.S. SERIES

5

FIG. 6. SHOWING DETAILS OF TRANSMISSION SHOCK ABSORBER

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Adjustable Magneto Platform. The tension of the magneto
driving chain can, on all A.J.S. machines, be adjusted in a very
simple manner due to the provision of a special design of platform

to which the magneto is secured. This adjustable platform is
shown in Fig. 8. As may be seen, the platform has a radial slot
which permits of the platform being tilted sufficiently to take up
any reasonable amount of slack. Two long threaded bolts pass
through the platform and screw into a tapped link on the opposite

THE BOOK OF THE A.J.S.

FIG. 8. ADJUSTABLE MAGNETO PLATFORM FOR TAKING UP

side. These only have to be loosened in order to raise or depress
the front of the platform.

Vernier Magneto Timing. All except 33/2 and “Maglita” models

have the patented system of vernier magneto timing, which enables
the magneto to be timed quickly and with great precision (see
page 125).

Inclined Engines. All A.J.S. motor-cycles except Models T5

and TB6 have their engines inclined forwards in the frame at an
angle of 16 degrees to the vertical. On the two models mentioned
the angle is 20 degrees. Besides facilitating cylinder removal this
enables the magneto to be placed behind the cylinder.

Big-port Engines. Round about 1925 some single-port models

were produced having unusually large diameter exhaust ports.
These machines had a reputation in the motor-cycle world for
their high turn of speed and general liveliness. It is therefore
satisfactory to note that two big-port models are available at the
present time. They are Models TB6, TB8. Both these machines
are genuine “mile-eaters,” and are much more flexible and

pleasing to drive than their predecessors.

Detachable S.V. Cylinder Head. One side-valve model (T9) has

CHAIN SLACKNESS

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a detachable aluminium alloy cylinder head designed so that

removal of the head for decarbonizing leaves the carburettor and
valves undisturbed (see Fig. 16A). The shape of the combustion
chamber is excellent with this arrangement, and the lightness of
the alloy results in a very appreciable reduction in weight.

Twin-port Exhaust System. Models T6, T8 have twin ports and
dual silencers of large capacity. This reduces exhaust noise to a
not unpleasant “zoom” to which no one can take offence. The

Model “T.6”

FIG. 9. THE 3.49 H.P. O.H.V. DE LUXE MODEL T6 (TWO PORT)

silencers, which embody the blind-ended drilled tube principle

with fishtail ends, are substantially made of sheet steel and are

heavily chromium plated.

Improved Mechanical Lubrication. This system, where the oil

in a separate tank is fed to and circulated throughout the engine
by a double-action mechanical pump, is used on all S.V. and

O.H.V, “singles.” Once the correct regulator setting has been

obtained no attention is necessary other than occasional draining
of the crankcase and regular replenishment of the oil tank.

7

THE 3.49 H.P. O.H.V. DE LUXE, TWO-PORT MODEL T6

This machine, which is one of the fastest "three-fifties" on the
road, combines the acceleration of a sports machine with the
smooth running and flexibility of a touring machine. It can be
ridden “hands-off” below 20 m.p.h., is rock steady, and has a
beautiful “spongy” action of the brakes. At £50 it is indeed

cheap, having regard to its fine finish and complete equipment.
Its specification is as follows—

ENGINE. The power unit is of 74 x 81 m.m. bore and stroke

giving a capacity of 349 c.c. Two large diameter, alloy steel,

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tulip valves, hollowed out for lightness, are symmetrically placed

at 82½° to each other in the detachable cylinder head so that,
when seated, their heads are roughly flush with the walls of the
hemispherical combustion chamber; slightly in front, on the left­hand side of the cylinder, is a sparking plug with its electrode
points pocketed within the chamber. This arrangement is ideal,
having regard to instantaneous combustion, good cylinder

charging and exhaustion, and last, but by no means least, good
turbulence. On ail O.H.V. engines the exhaust valve guide is a
steel housing with phosphor bronze lining. The inlet guide is of

cast iron (except TB6). Lubrication of guides is not provided.

The valves are operated by polished duralumin rockers, splined
to the tubular rocker shafts, carried by a sturdily built rocker box,
which is fixed by four pins to the cylinder head. This rocker box
has an inspection cover in the centre of which is a Tecalemit nipple
for greasing the push-rod ball joints. Two coil springs fitted inside
the rocker spindles keep the rocker balls in contact with the rods
and also prevent rocker end play. The arms carry at their
extremities grub screws and lock-nuts, which enable valve adjust­ment to be effected at the rocker arms. The whole of the overhead
valve mechanism and the two duralumin push rods are totally
enclosed and adequately lubricated. With a hot engine the clear­ance between inlet valve and rocker is ·006 in,, and the exhaust
clearance is ·008 in. The rockers have large area plain bearings.
The crankcase valve actuating mechanism is, of course, the same
as on the S.V. engines. The valve springs are noteworthy, being

of the two-in-one variety. The valve movement slightly overlaps
the piston stroke, and in consequence two small segments are
milled off the piston crown to prevent fouling of the valves.

The piston is of aluminium alloy, and has four narrow width

rings, the bottom ring being primarily designed to prevent piston

slap. The gudgeon pin is hollow, and is secured in position by two
spring circlips. This piston, unlike many of its type, does not
suffer from that distressing malady, “piston slap.” The correct
gap at the rings is ·005 in. to ·010 in. The compression ratio is

6 to 1 with the standard piston, but a special high compression
piston giving a ratio of 7·5 to 1 is obtainable.

Within the cast aluminium crankcase is the crankshaft assembly,
comprising two heavy rimmed cast-iron flywheels of comparatively
small diameter, with their main shafts running in ball bearings,
and the crankpin upon which the big end roller bearing of the
connecting rod is mounted. Two ball races are fitted on the
driving side and one on the timing side. Those on the driving
side are separated by a white-metal, oil-retaining ring (see Fig.

40). This ring has its outside grooved and drilled radially so
that any oil reaching the ring is returned to the crankshaft.

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9

FIG. 10. THE 1932 OVERHEAD VALVE A.J.S. POWER UNIT

The engine illustrated is a 4·98 h.p. twin-port model T8, and is

shown with the Bowden carburettor. The 3·49 h.p. engines are
similar as regards external appearance. T6, TB6 pistons have
segmented convex crowns. All others have the fiat type chamfered

at the sides. During 1933, overhead valve A.J.S. engines will be

available as proprietary engines under the pseudonym “Majestic”

2—(5301A)

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The big end bearing is interesting, owing to the somewhat unusual

mounting of the rollers. The cage is of duralumin and the

rollers themselves lie end-to-end in the slots and between flanges
on the crank pin; the sides of the rollers are clear of the fly­wheel bosses, and thus there is no deleterious end thrust.

A disc-type crank case breather is not used on A.J.S. machines,

but merely a release pipe from the timing chest, a plain union
being screwed into the timing chest and the release pipe taken
from this. A non-return valve is not included, neither is it
necessary.

The timing gear is extraordinarily simple, and does its duty in
a noiseless and trouble-free manner. It consists of the engine
main shaft small pinion and two large half-time cam wheels. The
cams act directly on the tappets, no toggles being interposed, as
the tappets have half-moon feet.

The new type silencers and fishtails are very effective in reducing
the exhaust noise, and should absolutely guarantee the rider
against police prosecution for noise, which has recently become so
prevalent. The principle employed consists of the use of blind
ended, and drilled, extensions to the two pipes; and it is thus
utterly impossible for the gases to flow straight through. This

system was thoroughly tried out before being standardized for

use on the 1932 range of A.J.S. engines, and it was found that the

resultant back pressure was negligible. Both silencers and exhaust

pipes are heavily plated. A flange fixing now replaces a clip or
screw fastening on the induction pipe for the carburettor on all
except the T5 and 33/2 engines.

CARBURETTOR. A No.

automatic carburettor with bottom petrol feed is fitted, and the
standard setting is—jet 150; needle position, 2; type of valve,
6/4. This gives fierce acceleration and perfect slow running.
Twist-grip throttle control is provided. Petrol consumption at 30

m.p.h. is over 75 m.p.g. Riders who wish to fit an Amal “acceler­ation pump” should note that on nearly all A.J.S. engines a
conversion is simply effected. See notes on page 81.

IGNITION. The current is generated by a H.T. Lucas variable

ignition type M.S.I. magneto chain driven off a sprocket splined

to an extension of the inlet camshaft. The other sprocket fits
on a sleeve keyed to the armature shaft, and has a vernier adjust-

ment for securing accurate timing. Actually, the flash across the

plug electrodes is timed to occur 9/16 in. before the top of the com-

pression stroke on full advance. The sparking plug used is the

Lodge H.1. The magneto is a well-protected instrument, and

has, of course, a clockwise armature rotation, viewed from the

contact-breaker side. A circular cover held in place by a spring
gives access to the magneto sprocket and vernier adjustment.

THE BOOK OF THE A.J.S.

76/014A

Amal, 2 jet, 2 lever, semi-

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11

LUBRICATION.

pressure-fed into the crankcase by a duplex pilgrim pump con­tinually, but a portion of the oil fed to this pump is returned to
the tank before entering the engine (see page 88). The flywheels
splash it on to the cylinder walls, and oil is also pressure-fed into
the timing case, whence it drains to the sump. The pump is
driven from the crankshaft and enclosed within the timing cover.

Both upper and lower plungers are connected by a common lead.
The upper plunger delivers oil to a false bearing on the timing end
of the crankshaft, and thence through the crankshaft and flywheel
to the big end. The lower pump returns some oil direct to the

Mechanical lubrication

FIG. 10A.

TWO-PORT O.H.V. CYLINDER HEAD

is

employed.

Oil is

(From “ The Motor Cycle.”)

FIG. 11. SHOWING NEAT CONCEALMENT OF THE OIL PIPES

tank, where the functioning of the pump can be verified by the
outflow from the return pipe placed immediately below the filler
cap and visible on its removal.

Mechanical lubrication undoubtedly relieves the rider of a

source of constant anxiety and annoyance; and also saves him

no small amount of money in the long run on the score of economy
in engine oil. Moreover, correct lubrication ensures the minimum

production of carbon deposits on the piston crown and combustion
chamber, and thereby gives the maximum mileage before the

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rather odious, but nevertheless easy, job of decarbonization

becomes necessary. This mileage should approximate 2,000.

In practice, however, the owner usually “decokes” as soon as an
appreciable loss of power and tendency to “knock” become
manifest.

The makers recommend the use of only the highest quality oil
for lubrication. Castrol “X.L.” and “C” are highly recommended
for touring and Castrol “R” for racing.

FRAME AND FORKS. These two supplementary units have been

THE BOOK OF THE A.J.S.

FIG. 12. THE STURDY SEMI-CRADLE FRAME

designed to give together a reasonably short wheel base (56½ in.),
and a 29 in. saddle height. Care has been taken to ensure good
general stability at speed and on treacherous road surfaces. The
A.J.S. forks are of the original 1930 pattern, and efficient shock
absorbers are incorporated at the rear end of the lower fork links.
The links are adjustable for side play. Fitted to the forks is a
very neat design of mounting (see Fig. 14A), which permits of a
lamp being bracketed in a very low position that greatly enhances
the appearance. A centrally placed compression spring is em­bodied in the forks, and a steering damper included on all 3·49 h.p.
and 4·98 h.p. models. This produces excellent steering without
looseness, and the efficient steering damper when tightened down

prevents any possibility of speed wobble occurring. The forks

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are provided with grease-gun lubrication. The frame is of tri­angular form of high tensile steel tubing. As may be seen in
Fig. 12, the frame is really a semi-cradle type with torque tubes
to the fork ends, which absorb all torsional stresses of the trans­mission. The bottom bracket and rear engine plates are in one piece,
thus affording great strength and rigidity. The saddle pillar tube
also extends right down to the lower cradle plates and torque
tubes. A single rail only is employed for the top tube, this being
of very large diameter.

GEAR-BOX. The gear-box is an A.J.S. countershaft four-speed

gear, fitted throughout with ball bearings, and is standard for two
models. It is operated by a right-hand gate change lever, affixed

to the tank on the right-hand side ; and it gives solo ratios of 5·8,
7, 12·6, and 17·4 to 1. Sidecar ratios: 6·41, 7·77, 13·9, 19·23.

Moving the change speed lever forward from front to rear

position, the consecutive gears engaged are—first; neutral;
second; third; top. On to an extension of the splined main shaft.
which has a very robust thrust bearing on the driving side, are
fitted two sprockets—one. small and one large—for primary and
secondary drives, respectively. The larger sprocket, incidentally,
is part of the clutch (see page 137), which is of the multiple plate
and cork insert type with multiple springs, and has handlebar
control on the left-hand side. No adjustment for clutch spring
tension is provided. The kick-starter lever (seen in Fig. 23) is in
a position such that ample leverage can be exerted upon it with
the foot while astride the saddle. Its operating mechanism is
entirely enclosed. Only a high grade oil made by a firm of repute
should be used for gear-box lubrication, and the oil recommended
is “Castrolease Light” for summer and Castrol “D” for winter.

TRANSMISSION. Both primary and secondary drive are by

substantial ½ in. pitch by ·305 in. wide Coventry roller chain.
The chain of the former is completely enclosed (Fig. 7), while that
of the latter has a protecting guard on the upper half only, giving
easy access to the chain for inspection and lubrication purposes.
These guards are designed to protect both rider and chains.

An efficient shock absorber on the engine mainshaft allows the
power to be absorbed gradually and thereby eliminates “snatch,”
which soon ruins any chain. In consequence, it is a very rare
occurrence for a properly tensioned and lubricated chain to break
on the road. The chain wears out completely long before this.

BRAKES, WHEELS, AND TYRES. Quickly adjusted, internal ex-

panding brakes are fitted to both front and rear wheels, which
are tyred with 26 in. by 3·25 in. wired-on, heavy type “Non­Skid” “Firestones” with Schrader valves. The rear brake is
operated by a foot pedal on the left-hand side and the front
brake is controlled by a handlebar lever on the right side. Both

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brakes are very smooth and powerful in action. Fig. 13 shows the

brake drum and shoes of the rear brake. Rear wheel quickly
detachable; both wheels have taper roller bearings.

TANKS. A handsome, black enamelled, and bulbous nosed.

saddle petrol tank of welded steel is secured by bolts to lugs on

the bottom frame tube, and has a capacity of 2 gallons of petrol.
The filler cap is of the snap action bayonet type. Fastened by
means of concealed plates are good quality rubber knee-grips.
Where an instrument panel is not or cannot be specified, the gear­box driven speedometer is let into a recess in the tank and held

THE BOOK OF THE A.J.S.

FIG. 13. SHOWING REAR BRAKE DRUM AND ANCHOR PLATE WITH

in place by two pins. The tank on T6, T8, T9 is finished in
chromium plating with a black panel and the usual transfer. A
separate oil tank behind the down tube holds 4½ pints. TB6,
TB8, T5 have black enamel finish and gold lining.

MISCELLANEOUS DETAILS. The semi- “T.T.” adjustable

handlebars have rubber grips with integral controls and in the
centre a steering damper ; just below the engine plates are rubber
footrests, adjustable for position. This combination gives a very
comfortable and natural riding position. The saddle itself is a
Lycett medium weight model, with special adjustable mounting
(Fig. 2). Valanced mudguards are fitted. Over the rear mud­guard is a strong detachable carrier capable of safely supporting
a passenger; but it is not exactly a flapper-bracket (to use the
latest newspaper description of a pillion seat) ; it is really intended
for luggage. Between the rear fork stays are secured two pannier
bags with a full kit of tools. A central spring-up stand is provided.
The general finish, including the handlebars, is black enamel on
a special anti-rust process. The usual parts are all heavily plated.
All oil and petrol cocks are of the quick action, push type. Elec­tric lighting (Lucas) is extra; see pages 2, 26.

SHOES

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THE 3.49 H.P. “BIG PORT” MODEL TB6

The specification of this machine, which is eligible for the

30s. tax, with electric lighting, provided it is licensed prior to

1st January, 1933, is the same as that of Model T6, except for
the following—

ENGINE. The engine has a bore and stroke of 74 X 81 mm.,
but instead of there being two exhaust ports there is only one port
tapering to 2 in. diameter at the outside. Through this large port
the products of combustion emerge at high velocity, and there is
no decrease of efficiency caused by having a single port. In

FIG. 13A. THE 3.49 H.P. O.H.V. MODEL TB6 (BIG PORT)

15

this engine a three-ring piston is fitted. Both inlet and exhaust
valve glides (80°) are steel housings with phosphor bronze linings.
There is, of course, also only one silencer of somewhat different
shape from that fitted on Model T6. No fishtail is provided, but
the end of the tail pipe is “pinched.” The carburettor is an Amal
of exactly the same type and setting as that fitted to model T6.
A Lucas “Maglita” or N.S.A.1 magneto is fitted. Ignition timing

is 3/8 in. before T.D.C., and the compression ratio is 6·5 to 1.

GEAR-BOX. This is a Sturmey-Archer three-speed light-weight

B.W. with enclosed kick-starter mechanism and two-plate clutch.

Instead of the clutch having several springs arranged radially it

has one large central spring only. The standard gear ratios
are 5·25, 8·12, and 15·45 to 1.

Other variations in specification are the provision of 25 in. x
3 in. tyres, non-valanced racing type mudguards, (the rear of

which is not hinged), a petrol tank of 1¾ gal. capacity and an

oil tank of 3½ pints. No carrier is fitted (though this can be had

as an extra) and no instrument panel is or can be specified, a

16

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Lucas "Maglita" lighting set being used instead of the "Mag­dyno" set on electrically equipped models. Also a rear stand is
used instead of a central spring-up stand. Wheel base is 52 in.

THE 4.98 H.P. DE LUXE O.H.V. TWO PORT MODEL T8

This machine has an appearance absolutely identical to that of
Model T6, and as a matter of fact it is a more powerful version of
this machine. The main differences in specification are as follows—

ENGINE. The general layout of this engine, whose predecessors

have performed so creditably in the Tourist Trophy Races, is

THE BOOK OF THE A.J.S.

Model “T.8”

FIG. 14. 4·98 H.P. O.H.V. TWO-PORT

similar to that of the 3·49 h.p. O.H.V. engine; some parts are
actually interchangeable. The machine illustrated has, it will be
noticed, a Bowden carburettor, but an Amal is now standard. It
is of 84 by 90 mm. bore and stroke, giving 498 c.c. capacity. Like
Model T6 engine, it is fitted with a detachable cylinder head,

enclosed valve lifter mechanism, an aluminium alloy piston with
non-segmented crown, and compound type valve springs. The
correct valve clearance is ·006 in. for the inlet and ·008 in. for
the exhaust valve, and the ignition advance, 7/16 in. before T.D.C.

Model T8 is undoubtedly very fast indeed. Its full throttle
speed, as given by the manufacturers, is 78 miles per hour. It
should attain this speed after careful running-in. The utmost care

is taken in the erection, tuning, and testing of every machine.
There is no doubt, however, that the crack rider who has the time,
skill, and patience available can still further improve upon this
very excellent performance and, given a certain amount of luck,
could “boost” the machine up to a speed of 85 m.p.h. To attain

such a speed it is not necessary to run on anything except petrol­benzole, using a high-compression piston and well-tuned car­burettor. As a matter of fact, two aluminium pistons are available
for this machine. One is a low-compression member for use with

ordinary petrol or petrol-benzol mixtures, and gives a compression
ratio of 5·7 to 1. The other is a high-compression piston which pro­vides a ratio of 7·5 to 1. This is a comparatively high ratio, and
permits of every available ounce of fuel energy being utilized
in the production of power with the rapidity of combustion at
its highest value. Only by exceptionally rapid and complete
gas combustion can mean piston speeds of approximately 30 m.p.h.

be obtained (and this is the piston speed corresponding roughly

to a road speed of 90 m.p.h. with a gear ratio of 5 to 1). It needs

little imagination to realize what large inertia forces the connect-

ing rod and bearings are called upon to resist in view of the fact

that at 90 m.p.h. the piston is undergoing alternately positive
and negative accelerations of a very high order nearly 200 times

every second! The connecting rod and double row ¼ in. roller

bearings fitted to the big end are thus of very robust construction
to stand up to the gruelling ordeal to which, on occasions,
they are submitted. The engine mainshafts rotate on ball

bearings.

An Amal type 29/004 carburettor is fitted and the setting is:
jet 180, valve 29/4, needle position 2. It is semi-automatic, and
has twist-grip control. The ratios of the four-speed gear-box are:

1st, 4·81; 2nd, 5·8; 3rd, 10·4; 4th, 14·4 to 1. Various parts
of the engine and machine have been slightly stiffened to with­stand the very high speed which this model is capable of
attaining. Recommended sidecar gear ratios are 5·53, 6·7, 12·0,

FIG. 14A. SHOWING A.J.S. FORK SUSPENSION AND HEADLAMP MOUNTING

THE A.J.S. SERIES

17

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18

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16·5 to 1. A carrier is fitted. Fuel consumption is 70-75 m.p.g.,
and oil consumption about 1,200 m.p.g.

THE 4.98 H.P. O.H.V. “ BIG PORT ” MODEL TB8

This, the largest "big port" machine, has the same specification
as Model T8, except that the twin exhaust system has been
scrapped in favour of the single port, a three-ring piston is used,
and the equipment does not include a carrier. The compression
ratio is 6·1 to 1, and the magneto advance 9/16 in. before T.D.C.

THE BOOK OF THE A.J.S.

(From “ The Motor Cycle ”)

FIG. 15. OIL RETAINING TAPPET GUIDES ON

THE S.V. ENGINES

Racing type mudguards are used, and the three-speed ratios are:
4·8, 7·0, 12·85, solo, and 5·53, 8·12, 14·7, S/C.

THE 3.49 H.P. STANDARD S.V. LIGHTWEIGHT MODEL T5

This machine, priced at the remarkably low price of £38 10s.,

is the second of the lightweights taxed at 30s. It is a smart little

machine with quite a snappy performance, and makes an excellent
general touring machine. It is capable of accelerating rapidly
to the mile-a-minute mark without “fuss.” The specification is

as follows—

ENGINE. This, like all the other engines, is of A.J.S. design
and construction. The keynote of the design is simplicity and
sturdiness. It is a side valve, inclined single cylinder, four-stroke
engine of 74 mm. bore, and 81 mm. stroke, giving a capacity of

349 c.c., or (according to A.C.U. rating) 3·49 h.p. A four-ring
aluminium-alloy piston reciprocates in a cast-iron cylinder with
horizontally finned, non-detachable head. The head on the T5

THE A.J.S. SERIES

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cylinder departs from earlier A.J.S. practice in that no longer is
the hitherto special A.J.S. method of holding down the cylinder
retained; this comprised a central bridge piece and two long bolts
with turnbuckle adjustment. In this head large non-inter­changeable and mechanically operated valves of heat resisting
alloy steel are placed side by side in deep pressed-in cast-iron

guides. The large area of these valves ensures perfect charging and

scavenging of the cylinder, besides giving good heat dissipation

and freedom from distortion and pitting of the valves themselves.

FIG. 16. THE 3.49 H.P. STANDARD LIGHTWEIGHT MODEL T5

19

The tappets operating these valves have, of course, adjustable

heads to give correct clearances of ·006 in. and ·008 in. in the
case of the inlet and the exhaust valves, respectively, when the

engine is hot. They also have oil retaining guides (Fig. 15).

A valve chest cover completely encloses the valves and springs.

Internally the engine is practically the same as the 3·49 h.p.

O.H.V. unit already described in detail. It has the improved type
of mechanical lubrication, roller bearings to the big end of the

connecting rod, ball-bearing main shafts, and a flat crown alu­minium alloy piston. The compression ratio is 4·3 to 1. As on all
present engines, the magneto is placed in a sheltered position
behind the engine. The correct spark advance, which is given on
page 20, can be accurately determined by means of the vernier
adjustment for the magneto sprocket. The exhaust system is
similar to that on the O.H.V. lightweight. Castrol “X.L.” or

“C” is recommended for engine lubrication.

Carburettor. This is a semi-automatic Amal instrument (type

5/148) with twist-grip throttle control. Unlike all other models

it has a screw-in fastening. Recommended combination for low

20 THE BOOK OF THE A.J.S.

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consumption, and beat performance are: Jet, 100; valve, 5/4;

needle position, 4. Petrol consumption is 90-95 m.p.g.

Ignition. Either a Lucas magneto or the Lucas “Maglita”

chain-driven from the inlet camshaft, and the spark advance is
7/16 in. before T.D.C. The sparking plug is a Lodge H.1.

The rest of the specification is the same as that of the O.H.V.

lightweight (TB6) except that the three-speed gear-box gives

ratios of 5.8, 9·1, and 16 to l. The machine is illustrated on page 19.

THE 4.98 H.P. DE LUXE S.V. MODEL T9

As may be observed from the illustrations, the general specifica-

tion of all the heavyweight models is practically the same. In

FIG. 16A. THE CAR TYPE DETATCHABLE CYLINDER HEAD ON THE

this instance model T9 is the S.V. counterpart of the 4·98 h.p.

de luxe O.H.V, model and has the same bore and stroke. Actually,
apart from the engine and carburettor, the only important differ­ence is that a three-speed gear-box giving ratios of 4·81, 7·06, and

12·85 to 1 is fitted as standard. S/C ratios—5·53, 8·12, and 14·7.

ENGINE.

O.H.V., model except, of course, that a different valve timing is
used. The piston is of aluminium alloy, and has the usual four
rings. The cylinder in which it reciprocates has six broad
horizontally-arranged fins, and contains the valves as shown
in Fig. 16A, a special car type aluminium cylinder head being

bolted to the top of the barrel with seven bolts. A copper and

Below the cylinder the engine is the same as the

4.98 H.P. S.V. MODEL

THE A.J.S. SERIES

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asbestos gasket is used between the two. The compression ratio

is 4·9 to 1. As is self-evident, removal of the cylinder head

does not mean unfastening the carburettor or interfering with the

valves—a meritorious feature from the point of view of the rider
who likes to devote a minimum of time to top overhauls. The
valves, springs, and tappets are all enclosed, as shown by a quickly­detachable cover plate, no valve caps are wanted. Correct tappet
clearances are ·006 and ·008 in. with a hot engine for inlet and

exhaust respectively. Castrol "X.L." or "C" is recommended,

and the magneto timing is 3/8 in. before T.D.C. fully advanced.

21

Model "T.9"

FIG. 17. THE 4.98 H.P. DE LUXE S.V.

CARBURETTOR. The carburettor, which is bolted by its flange
direct to the cylinder barrel, is a bottom feed, semi-automatic
6/004 Amal with 140 jet, 6/4 valve and needle position 3.

THE 9.90 H.P. STANDARD S.V. (1933) BIG TWIN

On going to press the author finds that the reintroduction of
the famous Big Twin, referred to in the Preface of this handbook,
has become a fait accompli. On 7th July, 1932, details of the two
Big Twins, which are really advance 1935 models, were announced.
They bear a close resemblance to earlier A.J.S. machines of this

type, although greatly improved and of thoroughly up-to-date

design. Two models are available, the Standard model and the
“Export” model, and their prices are, without Lucas electric
lighting, £65 in each case. The Standard model has the following

specification—

Engine. This engine has a bore and stroke of 85·5 mm. X
85·5 mm., giving a cubic capacity of 990 c.c. The two cylinders
are set at 50 degrees to each other, and the bores, being “square”

22

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THE BOOK OF THE A.J.S.

with the cylinder castings, the firing angle is also 50 degrees.
Pig. 19 shows the general design and construction of the power
unit.

The crankcase itself is a very neat aluminium casting split

longitudinally in the usual manner. An extension immediately

below the annular timing case, which has a readily detachable
cover, houses the dry sump plunger, and if separation of. the

crankcase halves is contemplated care is necessary in respect of

this unit. A disc breather maintains atmospheric pressure in the

FIG. 18. CONNECTING-ROD MOUNTING ON TWIN

Left is shown a 1930 assembly. The crankpin on the new 33/2 engine
has parallel location in the flywheel. It is flanged on either end of the
“run,” ¼ in. x ¼ in. rollers are used, and these run in a small metal cage.
No separate big-end liner is used in the connecting rod and the diameter
of the gudgeon pins are now much larger. Where the connecting rods were
offset on the small end of the earlier engine, they are now square with the
connecting-rod, and the small-end bush stands out farther on one side than

the other. On the right is shown the detachable fabric filter in the oil tank

CYLINDER ENGINES

FIG. 18A. FABRIC

FILTER

crankcase. An oil bath (Fig. 7) lubricates the primary chain.

The crankshaft assembly is an ordinary single-throw type built up
of two flywheels, to which are keyed the friction fitting mainshafts,
and a flanged crankpin upon which, with two sets of caged rollers
interposed, but no bushes, are mounted a pair of “H” section
connecting rods having 7/8 in. (I-D) phosphor-bronze small end
bearings. With regard to the crankshaft bearings, that on the
driving side has a heavy double-row caged roller bearing, while
the other one is of the plain bush type. The pistons themselves
are of aluminium alloy and have four rings each, the lower acting
as a scraper ring. They are split diagonally across the skirts to

THE A.J.S. SERIES

23

allow for expansion, and they have fully floating gudgeon pins
secured by small spring circlips to prevent scoring. With a

cold engine the correct gap at the piston ring slots is ·005 in. to

·010 in. Permissible crankshaft end play is ·025 in.
The cylinders, which have a compression ratio of 4·8 to 1, have

cast-iron detachable heads, and the cylinder barrels are cast

integral with two very neat valve chests which entirely enclose and

protect the valves and their springs, two pressed steel cover plates

held firm by centrally placed knurled nuts giving instant access to

the valves. The. barrels are deeply spigoted at their bases and

paper washers are used; C. and A. gaskets are fitted between the

barrels and heads, which are of semi-turbulent design. The

F I G .

19.

CLO S E-U P V I E W OF T HE

9·90

H . P.

33/2

E N G I N E

The timing case cover and one valve cover plate have been removed to
show the valves and timing gear. The induction manifold and carburettor
are also removed. It is of interest to note that this engine is identical to

that installed in the Matchless Big Twins

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24

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sparking plugs are not centrally located over the cylinder heads,
but are placed in an offset position over the inlet valves. The two
cylinders are interconnected by a horizontal induction manifold

with screw-on unions.

The valves themselves arc of large diameter and of the mush­room type with single springs and slotted valve stems for the flat
cotters used for anchorage. They reciprocate in chilled cast-iron

guides which are readily detached for renewal. Round section
tappets are used, and the adjustable heads screw into the tappet

bodies and are secured by lock-nuts. The timing gear is extremely

simple. It comprises a single cam wheel having three cams, one
each for the exhaust and one for the inlet valves, driven off the
engine pinion, and four toggles mounted on pivot pins and separ­ated from the back of the timing case by
The arrangement of these toggles is shown by Fig. 19, and the

neat exhaust valve lifter mechanism in the centre is also clearly
illustrated ; the timing pinions are marked for mesh. The products
of combustion are swept out from the exhaust ports into an im­posing and exceedingly quiet exhaust system comprising two

1¾ in. diameter chromium plated pipes, each terminating on the
off side in a standard A.J.S. silencer and fish-tail.

The magneto, or "Magdyno," as the case may be, which is

mounted on a platform above the gearbox, is driven by chain and

sprockets direct off the camshaft. The camshaft sprocket fits on
a slight taper, is not keyed, but held firmly by a nut screwed to

the threaded end of the shaft. Chain tension is adjusted by tilting
the special magneto platform (Fig. 8). A chromium plated and
black-enamelled pressed steel chain case protects the chain.

The lubrication of the engine is carried out by a D.S. system
similar to that described on page 88. The double-acting oil pump
forces oil under pressure to the big ends of the connecting rods,
the mainshaft bearings and the camshaft bearings, while the
whole of the timing gear runs submerged in oil, the surplus being
returned to the crankcase through a small oil level hole.

With this lubrication system there is no means of adjustment

provided as on the other models.

Tappet clearances ·004 in. inlet and ·006 exhaust (warm)
Magneto advance

CARBURETTOR. This is a No. 6/012 Amal. Particulars: main

jet, 140; needle valve, 6/5, in position 2.

IGNITION. Lucas magneto behind the engine without vernier tim-

ing adjustment. The magneto sprocket is not keyed to the arma­ture shaft, but is a tapered friction fit. Lodge H.1 sparking plugs.

LUBRICATION. On the Big Twin the lubrication system is of

the dry-sump type, different from that used on the 1933

“camshafts.” It differs absolutely from the improved mechanical

THE BOOK OF THE A.J.S.

29

/64 in. distance collars.

7

/16 in. before T.D.C. on full advance

THE A.J.S. SERIES 25

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lubrication system fitted to the 1932 range of six machines. A

half-gallon oil tank with fabric-type oil filter is mounted on the

seat tube. On the instrument panel (Fig. 19A) is an oil tell-tale.

This should indicate pressure when the engine is running.

FRAME. This is a semi-cradle design with a very robust scat

post, twin tubes running from the front of the power plant and
swept to the rear wheel spindle, and a very large-diameter top
tube. Standard A.J.S. forks are used except that the shock
absorbers are adjustable by a hand-wheel on the off-side. There
is also a steering damper.

TRANSMISSION. 5/

in. pitch by 3/8 in. wide, Coventry rear chain,

8

oil tell-tale

FIG. 19A. SHOWING OIL TELL-TALE ON INSTRUMENT PANEL

totally-enclosed ½ in. by ·305 in. front chain with oil bath and
shock absorber on engine mainshaft.

CLUTCH AND GEAR-BOX. The clutch is of the multiple plate

and cork insert type, hand controlled. Gear-box is a four-speed,
pivot mounted, Sturmey-Archer, with ratios of 4·5, 5·5, 7·3, and
13·5 to 1 solo.

WHEELS, TYRES, AND BRAKES. Both of the wheels quickly

detachable and interchangeable, with 27 in. by 4 in. wired on,
heavy type, non-skid Firestone tyres. Brakes of internal ex­panding type with 7 in. front and 7¾ in. rear diameter drums and
dust and water-excluding flanges. The front and rear brakes are
operated by a lever and foot pedal situated on the right and left­hand sides respectively, quick finger adjustment being afforded.

TANKS. The petrol tank has capacity for 3½ gallons of petrol,

which is sufficient for 150-200 miles. On the top of the tank is a
flush-fitting instrument panel with the oil tell-tale. The oil tank
holds four pints. Standard A.J.S. finish.

MUDGUARDS. Well valanced, and fitted with drip channels.

Rear : 6f in. wide, with detachable portion for wheel removal.

MISCELLANEOUS. Included in specification are—-Lycett saddle,

semi-sports handlebars, rubber footrests, stands to front wheel

3—(5301A)

(From “The Motor Cycle”)

26

THE BOOK OF THE A.J.S.

and central spring-up stand, a complete set of tools. Lucas
electric lighting costs £5 17s 6d. There are also various extras
obtainable, such as an 8-day clock, electric horn, gearbox-driven
speedometer, etc.

THE 9.90 H.P. S.V. “EXPORT” MODEL

The specification of this machine differs from the standard
model in regard to a few points only. The main differences are
as follows—Long touring handlebars are provided. A left-hand
gear change is used. There is a ratchet control for the foot brake.

The clutch has foot control. Rubber footboards are specified

instead of footrests. An air cleaner is fitted.

1933 MODIFICATIONS

The six 1932 models are being continued for 1933, with the
exception of the 349 c.c. big port lightweight model TB6. This
machine will be replaced by a 248 c.c. model having a very similar
specification ,and costing £41 10s. It will be known as model
33/12, and will be taxed at 30s. under the new licensing regula­tions. The other five models (which incidentally will be known as
models 33/6, 33/8, 33/B8, 33/5, 33/9) will be unaltered except in
regard to a few minor details. The raised type of tank-mounted
instrument panel (Fig. 1) will be scrapped in favour of a neat flush
fitting panel (Fig. 19A). This panel, which, with complete lighting
equipment (£5 17s. 6d.), will be available as an alternative to the
plain "Magdyno" lighting set (£5 10s.), with switch situated on
the back of the headlamp, will include the main lighting switch, a
combined panel and inspection light, an ammeter and provision

FIG. 20. THE 33/2 “EXPORT” MODEL

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THE A.J.S. SERIES

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for a Smith 8-day clock (80s. extra). The Smith speedometer,

where specified with instrument panel, will be fitted on the front

of the handlebars ; otherwise it will be fitted on the tank. Hand-

operated shock absorbers will be provided in addition to the

steering damper on all models. On model 33/B8 a foot gear change

and upturned exhaust pipe will be optional.

1933 Camshaft “Trophy” Models. Apart from the Big Twins

and the little " two-fifty," the only other entirely new machines
in the 1933 programme are the two eagerly awaited overhead
camshaft models, which are to be known as “Trophy” models in

view of Mr. G. Rowley's line performance on one of them as a
member of the team which brought back the International Trophy
to England in 1932. The “Trophy” models will be known as

Models 33/7 and 33/10, and will have engines of 346 c.c. and

495 c.c. respectively. Prices will be £65 and £70 respectively.
Both models will have a very similar specification, and each will
be obtainable in racing or competition form. The racing form
will have a straight-through exhaust, no kick-starter, two pairs
of footrests, a mudguard pad and specially tuned engine with
alternative pistons giving compression ratios of 7·5, 9, and 11 to 1.
The competition form will have an upswept exhaust pipe with

tubular silencer, a kick-starter, a special crankcase shield, and

compression ratios of 7·5 to 1 and 6 to 1 in the case of the 347 c.c.
and 495 c.c. models respectively.

The single-port engine is an improved version of the 1929 type,
with camshaft driven by an automatically tensioned chain, but
the magneto is now placed behind the cylinder, and the dry sump
lubrication system incorporates in addition to the usual gauze
filter a fabric filter in the tank of the same type as that used on
the Big Twins. A duplex pump similar to that fitted to the
magneto chain cases of the series “T” machines forces oil to the
main shaft bearings, the big end bearings and timing gear, and
also to the rocker box and both valve guides. All the oil in the

tank is constantly circulated. 14 mm. plugs are used. The whole

engine (see page 114) has been thoroughly cleaned up.

The specification includes a pivot mounted 4-speed S.A. gearbox

with foot change, a 3 gallon fuel tank, twin float-chamber Amal

carburettor, detachable rear wheel, hinged mudguard, adjustable
saddle, and 26 in. by 3·25 in. tyres. A speedometer and engine
revolution counter to match, as well as “Magdyno” electric light-

ing, with or without panel, can be fitted on both models 33/7
and 33/10 as extras.

A.J.S. Sidecars. Three sidecars will be obtainable during 1933.

They will be model “A” Sports (£18 10s.), model “B” Launch

(£17 10s.), and model “C” Occasional Two-seater (£25). For the

two-seater a spare wheel will be available at six guineas extra.

27

CHAPTER II

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VARIOUS PRELIMINARIES

IN this chapter we assume that the reader has selected and ordered
his new mount, and desires to get it on the road as soon as the
various legal formalities and requirements have been satisfied.

The absolute novice is strongly advised not to attempt to ride
the machine away from the works. This is courting disaster if
the route involves driving through much traffic. Often an expert
driver, who has been accustomed for years to driving a machine
with throttle control action working in the reverse direction to
that of the new machine, finds that he is not quite happy on this
mount for several days. As we all know, the subconscious mind
plays a great part in driving, and especially in a sudden emergency.
The strong probability is that, when confronted with sudden
danger and an instantaneous and unpremeditated decision has
to be made, the wrong action would instinctively be taken, that
is to say, the throttle would be opened wide instead of being
shut, or vice versa, with appalling results. This has actually
happened in quite a number of instances. The wisest course is
to make arrangements with the nearest agent to have the motor­cycle delivered for a nominal charge by one of his employees.
A.J.S. dealers are scattered widely throughout the United King­dom, and no difficulty should be experienced in this connection.
First supply the dealer with the registration licence before the

machine can be delivered. One of the largest and most con-

veniently situated spares stockists in the Metropolitan area is
H. Taylor & Co., Ltd., of 135 London Road, Kingston-on-Thames
(Branch: 2 Tichbourne Court, W.C.1). Buyers resident in London

would do well to purchase their spares direct from the manufac-

turers at Plumstead. It is also well to remember that at Plum­stead A.J.S. owners have at their disposal a comprehensive
A.J.S. Service Department capable of dealing with any repairs
and overhauls.

Registration and Tax. All motor-cycles are subject to registra­tion and taxation, and a machine cannot be used on the highway
until a registration number has been allotted to it and a licence
obtained from the local borough or county council office. This
registration or index number belongs to a machine until such
machine is no longer used on the highway. If, after expiry of a

licence, no renewal is made for a prolonged period, the authorities
must be informed of the reason in advance. In the case of motor­cycles the tax is to be on cubic capacity, not a weight basis.

28

VARIOUS PRELIMINARIES

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There has been persistent urging by many people for the reintro­duction of a petrol tax, but so far no change has been made.

On and after 1st January, 1933, 150 c.c. machines will be taxed
at 15s. per annum, 150-250 c.c. at 30s. per annum, and 250-1000
c.c. at £3 per annum.

A licence application form (R.F. 1/2) is obtainable from any head
post office, and must be very carefully filled in and posted to the
licences dept. of the county council in whose area the machine
is usually kept. Certain data, e.g. engine No. and frame No.,

will have to be first obtained from the dealer, if the machine is
not delivered by rail. On page 31 a portion of an applica-

tion form is reproduced. It will be observed that quarterly
licences as well as annual licences may be taken out at the rider's
discretion. Common sense dictates what licence should be taken
out under the prevailing circumstances. A point to be noted,
however, is that a post office can only issue renewals of the same
type as already existing, that is to say, that a quarterly licence
can only be renewed as a quarterly licence, and an annual one as

an annual one. Application for annual licence renewal must be

made between the 1st and 15th of January each year. In

calculating the weight unladen, the weight of all parts normally
used must be included, exception being given only in the case of
fuel, water, oil, accumulators, and loose equipment.* The regis­tration authorities, if they doubted the accuracy of a weight
declaration, might call upon the owner to have the machine
weighed on an approved weighbridge in the presence of authorized
officials. When selling a machine, the licence, if unexpired, may

be handed over to the new owner, and the registration book must
be handed over to the new owner, who is required to pass it on
to the registration authority after entering particulars of owner­ship. Both vendor and purchaser must notify the authorities
of the transaction. It should be thoroughly understood that
every taxation licence is issued for use with one machine, and one
only. It is kept for use with that machine, whatever changes of
ownership may occur. In the registration book all changes of
ownership are recorded, as well as full particulars of licences
issued. The book thus forms a complete record of the machine's
history, and, incidentally, is of no little interest to the purchaser

of a second-hand machine.

If a motor-cycle is registered as a solo machine, and the motorist
decides to attach a sidecar, he must take out a fresh licence,
and return the existing one, plus the balance due on a sidecar,

i.e. 20s. All 1932 solo A.J.S. machines, except models T5 and
TB6, are taxed at the rate of £3 per annum. These two lightweight

* In the event of the authorities requiring a TB6 to be weighed the tools must

be removed or it will be taxed at £3.

29

30 THE BOOK OF THE A.J.S.

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models, weighing under 224 lb., are subject to the 30s. per annum
tax provided their registration is effected before 1st January, 1933,
and they will thereafter continue to be taxed at this rate.

When the machine is on the road it must carry the licence—

which is in the form of a disc—in a conspicuous position, visible
always by daylight from the near side of the machine. The
licence should be carried in a weatherproof holder, and may be
mounted (1) on the front number plate, (2) on the handlebars,
(3) at the side of the tank, (4) in the case of sidecar machines on
the side panel of the sidecar body. The licence is of a distinctive

colour, which is changed annually, and therefore a police officer
can tell at a glance when an annual licence is out of date. Four­teen days' grace, however, is allowed from the expiry to the
renewal of an annual licence.

Driving Licence. It is unlawful to drive any motor vehicle on

the road without a driving licence bearing the rider's signature,
which may at any time be demanded by a police officer together
with a "certificate of insurance." Five days' grace is now allowed,

however, for the licence to be produced in person at a police
station specified. The fee for a licence is 5s., and it is valid
for one year from the day it is issued. Applications should be
made to the licences department of the county council in whose
area the motor-cyclist normally resides. If the applicant is 16
years of age, he can, subject to a certain standard of physical fit­ness, obtain a licence to drive a motor-cycle only; but if he be

17 or over, a licence enabling him to drive a car or motor-cycle
is, subject to the same condition, obtainable. For forging or
altering a licence, the offender makes himself liable to two years'.
imprisonment.

With regard to physical fitness, no test is compulsory, but a
driver is required to make a declaration on Form DF1 that he
suffers from “no such physical infirmity” as to render him a source
of danger to the public. A “source of danger” includes a man
having abnormal eyesight to the extent that he cannot read a
car number plate at a distance of 25 yd., has lost a limb, has

muscular paralysis, is liable to fainting or giddiness, or suffers
from any form of epilepsy. It should be stated, however, that if
after the licence application form has been filled up, the licensing
authorities are doubtful as to the driver's fitness, they may decline
to issue a licence, but the would-be motor-cyclist can demand an
official test for driving fitness, the fee for which is 10s. Defective
eyesight, epilepsy, or giddiness definitely bar a man from obtain­ing a licence. The penalty for making a false declaration is a fine
not exceeding £50, and if done deliberately may incur imprison­ment. The driving licence is strictly non-transferable, and is
liable to be endorsed or even suspended at the jurisdiction of any

VARIOUS PRELIMINARIES

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31

magistrate, under the Motor Car Act of 1903. No police officer
may lawfully peruse the endorsements at the back of a licence.

This eliminates prejudice that the officer might have against the
offending motorist before deciding to report him for contravening
the law. It is not, however, wise to roundly abuse an officer for
this, or for any other reason. Remember that the British police­man, in spite of all the intolerance often unjustly attributed to
him, is a very fair, reasonable, and just man, when treated with
due respect. When treated otherwise, however, he is a decidedly

stiff proposition to deal with.

PORTION OF REGISTRATION LICENCE FORM (1932)

Annual

I apply for a licence expiring* on 193 ,

for a :

MOTOR-CYCLE (or motor scooter or cycle

with auto-wheel or other motor attachment).

Note : Motor-cycles exceeding 8 cwt. in weight
unladen are chargeable to duty as cars.

(a) Bicycle—
Weight unladen, not exceeding 224 lb.
Weight unladen, not exceeding 224 lb. with

right to draw trailer or sidecar

Weight unladen exceeding 224 lb., but not

exceeding 8 cwt. .....

Weight unladen exceeding 224 lb. with right

to draw trailer or sidecar

(b) Tricycle (not exceeding 8 cwt. in weight

unladen) ......

* A refund can now be obtained for the unexpired period of a licence, on

surrender, so long as it is not less than one month.

Licences
expiring

on 31st

December

Duty

£ s. d.

1 10 ­2 10 ­3 - -

4 - ­4 - -

Quarterly licences

expiring on
24th March, 30th
Juno, 30th Sept.,

or 31st December

Duty

£ s. d.

8 3
13 9
16 6

1 2 ­1 2 -

Third-party Insurance. It is now compulsory for every motor-

cyclist to insure himself against third-party risks. Failure to do­so involves severe penalties. The law now requires that every

person knocked down by reason of careless or negligent driving
shall be able to recover from the motorist or motor-cyclist,
through the insurance company, damages up to £25 for every
accident he may be involved in. The premium for third-party
cover is very reasonable, being about 30s. per annum unless

pillion riding is indulged in or the policy covers the driving of
more than one machine, in which case a higher rate is charged. If
a pillion passenger is carried the insurance policy must cover

him, and likewise any sidecar passengers. On paying the insur-

ance premium and supplying all necessary information to the

company, they will issue to the applicant the all-important

32

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“Certificate of Insurance,” which must be sent with the driving
licence application form and afterwards produced on demand.
Riders already insured thereafter receive reminders from their
insurance companies before the policy expires, and on renewing
them automatically receive their new “certificates.” Altering or
forging a "certificate " is a criminal offence. If a certificate cannot
be produced on demand a summons will follow unless the rider
can produce the certificate at a police station specified within five
days.

In the case of a new machine it is, of course, desirable to take
out an insurance policy covering besides third-party risks damage
to the machine. If the machine is bought on the hire-purchase

system this will be insisted on.

It is best to take out a comprehensive policy with a reputable

company. Most insurance companies give no-claim bonuses. It
therefore does not pay to worry a company over trifling and
inexpensive details. All risks can be covered for a medium

power machine for about £6 per annum. The insured should guard
against any conduct likely to invalidate his policy. All clauses
should be very carefully studied and complied with ; otherwise
in the hour of need the insurance company will remain neutral
and repudiate liability, citing as its reason the violation of some
clause of its policy by the insured person, and the rider may have
to foot the bill himself.

Number Plates. It is not sufficient merely to have a number

plate on the machine. The number plate must be in accordance
with a definite scheme and definite dimensions laid down. Up till
6th October, 1930, both number plates were permitted to be in

accordance with the dimensions given at A (Fig. 21). This still
holds good in respect to the front number plate, but as regards the
rear plate new dimensions are now specified. They must be as
shown at B (Fig. 21). All letters and figures must be 2½ in. high,
with a total width for each letter or number of 1¾ in., except in

the case of the figure 1. Every part of every letter and figure must
be 3/8 in. broad. The space between adjoining letters and between

adjoining figures must be ½ in., and there must be a margin between

the nearest part of any letter or figure, and the top, bottom, and

sides of the black background of at least ½ in. The lettering if

placed above the numbers need not be centralized, but the letters
themselves cannot be separated more than the prescribed ½ in.,
and there must be ½ in. space between the bottom of the lettering
and the top of the numbers. The rear plate must be illuminated

after dark by a suitable tail light.

Audible Warning of Approach. The exhaust noise does not

come within this category ; the law stipulates that an independent
warning mechanism must be provided on the machine. This may

THE BOOK OF THE A.J.S.

VARIOUS PRELIMINARIES

33

be in the form of a mechanical, electric, or bulb type horn. They
all have their merits. For touring purposes a bulb type is suitable,
but for the sports rider, mounted on a fast and perhaps slightly
noisy machine, a mechanical horn, mounted on the handlebars,
or an H.F. electric horn, is invaluable. The ideal is to have two,
but do not buy one of those cheap horns which begin by sliding

FIG. 21. NU MBER PL ATE DIMENSIO NS

At A are shown the old dimensions still used for a front plate and at

B the new dimensions required for rear plates

down the handlebar towards the steering head, and end by dis­solving into their component parts.

Never use a horn unnecessarily—particularly the mechanical
type—for it is apt to offend people when thus used, and remember
the sounding of the horn with the machine stationary is technically
an offence!

Lamps. During the period between one hour after sunset and

one hour before dawn (summer time) it is compulsory to show a

white light facing to the front and a red one to the rear in the

case of both solo and sidecar machines. The sidecar lamps must

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34

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be fitted on the offside so as to indicate the entire width of the
vehicle. At present it is compulsory to fit a rear lamp, not just
a reflector. Recent legislation now makes it a punishable offence
to take any mechanically driven vehicle on the highway at night

without a red rear lamp fitted. Reflectors are allowed only on
pedal cycles.

Lighting sets are either of the acetylene or electric type. Elec­tric lighting is now becoming almost universal, and has revolu­tionized night riding; for there can be no possible doubt that it is

far and away the best of the two types. It is, of course, purely a
matter of expense. (See pages 2, 25.)

Other legal aspects affecting, chiefly, the conduct of the driver,

will be considered in Chapter III. We may assume that the

makers have complied with the law in the fitting of brakes and
sidecar. The former, however, must be kept in proper order,
otherwise a breach of the law is incurred.

Speedometer. Many people are apt to regard this instrument

as a pure luxury. This view is wrong ; it is practically a necessity.

By its agency both your tyre mileage and your fuel consumption

can be accurately estimated ; it is of vast service in watching the
tune of your engine by informing you when the machine is losing
speed, or climbing a hill slower than it used to do, and by indicat­ing whether any mechanical adjustments that you may have made
result in an increase of engine revolutions. Watching the fluctua­tions of a speedometer needle is at all times fascinating, and in
long distance tours the instrument is of great assistance. Tank­fitted or tank panel-fitted “Smith” speedometers driven from the
gear-box are not standardized on any model, but can be had as
an extra. The “Smith” can be fitted on all 1929-33 models.

All speedometers work on one of two principles—the centrifugal
or the magnetic—and the average cost of an instrument is £2 to
£2 10s. Most popular among the centrifugal type are the “Cowey,”
the “Smith,” and the “Watford.” The “Stewart” works on the
magnetic principle, however. All these instruments are wonder­fully accurate, arid require little attention. An ultra-modern
instrument is the “Bonniksen” time speedometer, which registers
both time and distance, thereby elucidating the average speed.
Those owners of early A.J.S. motor-cycles are strongly advised,
also to fit one of the above mentioned instruments to their

machines; a front wheel drive is easily arranged.

Joining a Club. At the present time there are numerous clubs

throughout the country that are willing to accept members for
a small fee. These clubs frequently hold meetings, including hill
climbs, reliability trials, and social events. There is no doubt that
one derives many advantages from joining a local club. But if you

value your machine do not enter for one of those freak scrambles

THE BOOK OP THE A.J.S.

VARIOUS PRELIMINARIES

35

which occasionally take place, which assume the form of paper
chases, in which paper is substituted by fragments of the lead­ing pack in the form of fish tails, silencers, and sundry loose
equipment. Enter for the more sober reliability trials and lull

FIG . 21A. THE 1933 OVERHEAD CAMSHAFT IN COMPETITION FORM

climbs. For competition and track racing the new overhead
camshaft A.J.S. shown in Fig. 21A is an ideal mount.

Besides these smaller clubs there are three great road organiza­tions, one of which it is advisable to join. Innumerable benefits
are obtainable on payment of a nominal annual subscription.
They comprise, among other things, free legal advice, “get­you-home” schemes, general road assistance, and use of road
telephones.

In some cases the smaller clubs are affiliated to one of these.
bodies. The addresses of these clubs are as follows—

Auto-Cycle Union, Royal Automobile Club,

83 Pall Mall, laP l Mall,

London, S.W.1. London, S.W.1.

Automobile Association and Motor Union,

Fanum House,

New Coventry Street, W.1,

This machine is available with a 3·46 h.p. or a 4·95 h.p. engine, and a racing

edition is available as an alternative to the competition type shown (see p. 27)

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CHAPTER III

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DRIVING HINTS AND TIPS

Preliminary Instruction. At this point in the proceedings we

take it that the reader's mount has been fully equipped for taking
the public highway, and is now garaged awaiting its first run on
the road. This first trip is always regarded by the “tyro” with
something approaching awe. Any preliminary nervousness, how­ever, disappears almost instantly on taking the road, and con­fidence is gradually, and then rapidly, acquired. Thereafter pro­gress is very rapid indeed, and after about a dozen runs or so

the rider usually feels capable of undertaking his first long cross-

country trip, and begins to thoroughly enjoy the sport; for
motor-cycling is undoubtedly one of the finest tonics in the world

for the average man, distracting, as it does, the mind from all
business and domestic worries. But the rider should guard
against becoming prematurely over-confident of his own abilities,
and keep his speed down to reasonable proportions for some
considerable time. Failure to do this usually results in his having
some hairbreadth escapes, which quickly remind him that he
is yet a beginner, and that, if he pursues his suicidal tendencies,
he will be a beginner somewhere else. Indeed, very high speed
should not be indulged in until the subconscious mind can be
trusted completely to carry out the various muscular control
movements automatically in the lightning emergencies which all
road users are bound to be confronted with, sooner or later.

We will now turn to the question of actually preparing for the
first run, which should be taken over a road well known to, the
rider and comparatively deserted. Firstly, it is advisable to read

carefully through the maker's instruction handbook, carefully noting

and, if possible, memorizing the more important details, especially
those regarding gear changing; for the gear-box, remember, is

a very expensive item of the equipment, and is subject to much
damage if carelessly handled. Then place the machine on its
stand by releasing the latter and dragging the machine upwards

and backwards upon it. Pump up the tyres if they need it (for

correct inflation pressures see page 46), and replenish the tanks.

When filling the petrol tank, which holds about 2 gallons, take

care to use a good size funnel with gauze filter when filling from a

can; otherwise you may allow dirt or grit to find its way into the

petrol system, and, perhaps, choke a carburettor jet, though this
is unlikely, since there are filters in the system itself. As regards

36

DRIVING HINTS AND TIPS

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fuel, the author would mention that No. 1 petrol is suitable for
all models except TB6 and TB8, where No. 1 petrol and benzol

(equal proportions) gives the best results. For racing, alcohol fuels
are desirable, but these require special compression ratios, and are
really beyond the scope of this handbook. Always replenish the
oil tank with the same lubricant. The A.J.S. Co. advise the use of
none but the finest brand of oil for lubrication. Any reputable
oil firm will give the reader advice on the particular grade to use.

37

FIG. 22. SHOWING PUMP UNIT AND OIL SUPPLY CONTROL

1926-28 A.J.S. machines had a sight-feed Pilgrim pump (left) driven by a dog
coupling off the inlet camshaft. To increase the oil supply rotate the milled
adjuster anti-clockwise. 1929-30 machines had dry sump lubrication without
a main supply adjustment. 1931-33 singles have a duplex pump (right)

The gear-box oil level should be roughly ascertained by removing

the lubricator at the side of the gear-box (see Fig. 57). Wakefield

“Castrolease” is recommended (for instructions see page 134).
Open the petrol cock by pushing the press button forward.

Engine Lubrication. All A.J.S. machines, except Big Twins
and O.H.C.'s, now have adjustable mechanical lubrication, so that
no attention whatsoever is required other than seeing that the
oil level in the tank is kept at the correct level and occasionally
draining the crankcase (see page 123). The amount of oil pumped
to the engine can be varied by altering the setting of the control
knob on the pump unit (Fig. 22). Screwing this knob down, i.e.
in a clockwise direction, cuts down the supply of oil, while turning:

with regulator

38

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it the reverse way increases the supply. As may be seen in Fig. 22,

a stop below the control knob prevents the oil supply being cut

right off. When the engine leaves the factory the oil supply is set

on the generous side, and after the engine has been well run-in,
say after a mileage of 500 to 600, or if the engine smokes exces­sively, the control knob should be screwed, down about one-eighth
of a turn and then re-tested for about 50 miles. If the oil supply
is excessive, continue to cut it down by turning the control
knob a further eighth of a turn, and so on, until the correct degree

of lubrication is obtained. An approximately correct setting is

arrived at by screwing the control knob lightly down to the stop and
then unscrewing half a turn. If the lubrication system is functioning

correctly, oil should be observed flowing from the small pipe inside

the oil tank immediately below the filler cap.

On. 1929-30 machines the main oil supply was not adjustable.

but an auxiliary oil feed to the piston had a needle valve control.
When using these machines for racing, the needle valve, seen in
Fig. 41 should be unscrewed one or two turns. This feeds oil
direct to the piston. On A.J.S. motor-cycles designed 1926 to

1929, Pilgrim sight feed mechanical pumps were fitted, supple-

mented by an auxiliary hand pump. One increases the supply by
rotating the regulating disc on the side of the pump in an anti­clockwise direction 1/16 in. at a time, or giving a separate charge of

oil from the auxiliary hand pump. AN ENGINE SHOULD BE

LUBRICATED SO THAT ON ACCELERATING IN LOW GEAR A PUFF OF
BLUE SMOKE ISSUES FROM THE EXHAUST. Once this ideal is

obtained, leave the setting alone. While learning to drive,
the lower gears are used very much, and consequently lack of
good air cooling makes the engine rather hot. Therefore, before
setting out on the first run, it is advisable to give more oil than

would normally be given. To operate the hand-pump fitted prior
to 1929, depress the plunger to its full extent. This fills the barrel
with oil, and the plunger, being spring loaded, will automatically
ascend, and, while doing so, injects the oil directly into the crank-

case. The lubricator can be put out of action by depressing the

plunger, and fixing it in its fully depressed position by means of the
small catch provided for that purpose. In the case of an early
machine equipped with hand-pump only, a full charge should be
given every six or seven miles, and, when the engine is being
unduly worked, small injections should be frequently made.

Before actually starting up the engine, it is best to take a good

look over the machine and get thoroughly conversant with the
positions and actions of the various controls. Experiments may

afterwards be made with them with the engine running on the

stand.

The A.J.S. Controls. The reader should not merely content

THE BOOK OF THE A.J.S.

DRIVING HINTS AND TIPS 39

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himself with knowing how the various controls work, but he should
understand their exact functions. He should also understand
the four-stroke principle which is described in chapter V.

He will then not drive the machine like a Robot, but like an.
intelligent being. It is a popular idea that motor-cycling requires
little intelligence. This is not so ; skilful driving requires deep

FIG. 23. CLOSE-UP OF 1932 O.H.V. A.J.S. SHOWING ARRANGEMENT

concentration and thought. In fact, nearly all the faculties are

brought into active play while driving a motor-cycle ; and hence

the satisfaction and pleasure that the motor-cyclist derives.

Motor-cycle controls are of two types: (1) engine controls,
(2) cycle controls. The former are the most sensitive and impor­tant ; they are analogous to delicate nerves which convey impulses
from the driver's hands to the interior of the engine. If the
reader has ridden a three-speed pedal cycle, he will understand
the purposes of the gear-box. It is to be hoped, anyway, that he
has ridden a " push-bike," for he will then have no difficulty

in balancing the motor-cycle straight away. Moreover, he will

OF LUBRICATION SYSTEM AND GEAR CONTROL

40

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have acquired some road sense which only experience can give.
A sketch of the 1931, 1932, A.J.S. controls is shown in Fig. 25.
The engine controls are all mounted on the handlebars and com­prise four: (1) throttle twist-grip; (2) air lever, which on the
Bowden carburettor (page 82) is substituted by a mixture control
for starting and normal running; (3) lever for advancing and
retarding spark, (4) exhaust valve lifter. The two carburettor
lever controls arc mounted on the right-hand side of the handle­bars. A twist-grip {opening inwards) constitutes the throttle
which regulates the supply of gas to the engine, and a short trigger
below the inside of it the air lever, which likewise controls the

air supply. The air trigger is opened by pushing to the right.

Their functions will be explained in that section of Chapter V

dealing with the carburettor. The exhaust valve lifter, which may

be seen on the left-hand side, is primarily intended as a decom­pressor for facilitating starting. The magneto trigger advances
the spark by being pushed towards the right, except in the case
of some 1931 and earlier models where it is pushed to the left.
For all normal purposes it may be left on three-quarters advance,
except for starting, when it should be a quarter to half retarded
to prevent the engine back-firing, and thereby delivering a nasty
blow to the foot operating the kick-starter. The nove may dis-

regard this lever, leaving it on half advance.

The cycle controls consist of the clutch, the gear-change lever, and
the two brakes. The front brake for the present may also be
disregarded. Later on use both brakes simultaneously. The
clutch is for coupling up the engine to the gear-box. The general
principle of the latter should be thoroughly grasped.

Function of the Gear-box. This is made clear if the simple

principles involved are understood. The reader will agree that

work done is proportional to horse-power developed (neglecting
transmission losses). An engine may be called upon to do the
same amount of work climbing a gradient a quarter of a mile long
as it does on a level mile. The essential difference is that the rate
of work is much greater in the former case; that is to say, the
work is distributed over a shorter distance. Assuming the speed
of the motor-cycle to be kept constant in both cases, four times

as much work will have to be done in the same time. The number

of firing strokes in the case of a direct driven machine is, of course,
the same in both cases, and therefore the power of each stroke
will have to be increased by enriching the explosive mixture, i.e.

by opening the throttle. But suppose that the throttle is wide

open, and the output of work docs not exceed the load imposed by

gravity when climbing ; then, naturally, the machine will slow

up and probably stop. There is only one way out of the problem,
and that is to increase the number of power strokes until the

THE BOOK OF THE A.J.S.

Cycle”)

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Motor

“The

(From

1930-33

ON A.J.S. MACHINES MANUFACTURED

CONTROLS

OF THE

ARRANGEMENT

24, 25.

FIGS.

bottom gear position at the front of the gate ; also no air trigger is provided on machines with the Bowden carburettor

On the left is shown the control layout on 1930 series “M” machines of which a great number are in use to-day. On the right is the

arrangement on the 1931 series “S” machines and the 1932-33 “T” machines. The machine illustrated is a model TB8 without

instrument panel, but the controls are the same for all models except that on 4-speed models top gear position is at the rear and

4 —(5301A)

42

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power output is quadrupled in the given time. This means,
incidentally, quadrupling the engine revolutions. This can be
done by incorporating a gear-box whereby the ratio of engine
speed to rear wheel speed can be varied at the will of the driver.
The principle on which all gear-box designs are based is the fact
that the larger the circumference of a rotating wheel is, the
greater is the speed of any point on that circumference relative
to the axial speed. Thus a combination of wheels or pinions can
be arranged on a countershaft (i.e. a shaft between engine and
rear wheel) such that, by the engagement of different pinions of
varying sixes, variations of the relative speeds of engine and
rear wheel can. be obtained.

That destructive weapon of war—the tank—is a, good example
of how huge driving force can be obtained from a comparatively
small motor by the employment of a sufficiently low gear. Up
to a point the brake horse-power developed is proportional to
the engine revolutions, or (to use an apparently contradictory
statement) the power curve is a straight line. The reason for this
is apparent if a moment's thought is given to the subject.

The novice is recommended to experiment with gear changes
on the stand with the engine shut off. This may be done by
moving the rear wheel and coaxing the gears and dogs into

engagement. But never force a gear into engagement. The

gear-box is not designed for such treatment, and will not stand
it for long.

Starting the Engine. We presume that petrol and oil cocks

are left open. For easy starting the throttle setting is important.
To find the correct setting, first shut the throttle and air controls
right back. On machines with the Bowden carburettor there is

no air lever, but set the mixture control lever to the closed or
starting position. This mixture control lever corresponds to the
corrector or choke generally used on car carburettors. Now on
machines with lever control open the throttle about one-quarter
of its travel or less. In the case of twist-grip control the air
control is a separate trigger. The twist-grip is operated by turn­ing inwards to open and outwards to shut. Shut the twist-grip
right back, and then turn the twist-grip inwards very slightly so
that there is about 1/8 in. pull on the wire after you have felt the
resistance of the throttle spring. On models having the Bowden

carburettor 1/16 in. throttle opening is sufficient. For these settings

to be correct there must be no slack in the controls ; that is to say,

when the lever or twist-grip is shut right back, a slight movement

should begin to move the throttle; if it does not do so, the slack

should be taken up by means of the adjusting screw on the top

of the carburettor. Do not forget the throttle stop. Leave the
air level or trigger slightly open, unless the engine is stone cold,

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DRIVING HINTS AND TIPS

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when it is advisable to close it completely. The ignition lever or

trigger should be retarded about one-quarter or one-half its travel.

Before getting astride the saddle satisfy yourself that the gear
lever is locked in “neutral” position and flood the carburettor by

“tickling” the needle for a second (if is unnecessary to flood in the

case of the Bowden carburettor). Now raise the exhaust lifter

and engage the starter with the right foot. Turn the engine over

several times with the aid of exhaust lifter, thereby sucking the

mixture in. If is best to use the lifter merely for overcoming

compression. If this is done, full suction will occur on each inlet

stroke. Should an early pattern A.J.S. engine with cast-iron

piston be very stiff, if may be necessary to prime it by opening
the cock on top of the cylinder, and allowing a few drops of petrol

to enter by means of the small priming pipe provided. This
should free the “gummed” up piston. But do not prime unless
absolutely necessary. Then give one vigorous kick, dropping the
exhaust lifter just before the foot reaches the bottom. The engine
should now fire. Take the foot off the starter instantly it does so,
but do not allow it to spring back with a “bang” after starting the
engine. Bring the foot back with the pedal and thereby prevent a
heavy blow being given to the stop. If only a few muffled ex­plosions occur, open the air lever slightly and also give more gas.
The engine should then fire instantly. No Carburation difficulty
should be experienced once the engine warms up. As soon as the
engine starts push open the air lever or mixture control. When the
engine has just started from cold with the air or mixture control
fully closed it will be found that the mixture is very rich, so steadily
open the control until the engine runs smoothly. After the engine
has warmed up full air may be given. Never leave the engine
running by itself. As soon as the oil circulates properly, and the
engine gets into its stride, the revolutions will increase greatly,
and the throttle must be closed accordingly. In regard to easy
starting (as may be understood by referring to the context and
diagram of the Amal carburettor on pages 79-82) it is essential to
keep the throttle nearly closed, so as to induce a high velocity air
current over the smaller, or pilot, jet. Under such circumstances it
is worse than useless to attempt to start up with the throttle wide
open. Refusal to start is always due to some definite cause, and
repeated operation of the kick-starter under the same conditions
is futile, besides being very exhausting and exasperating. If the
engine does not start easily after the first attempt, the rider is
usually inclined to flood the carburettor excessively, and so cause
the mixture to become much too rich. In this case open the
throttle and air lever fully, raise the exhaust valve lifter, and
kick the engine over several times. This will result in the excess
petrol being cleared out. When starting with the engine warm

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keep the air lever or mixture control fully open. Most modern
machines, however, are not addicted to starting trouble, except
on rare occasions. We will deal with these and their remedies
later.

A tip worth noting is, “Don't go out for a ten minute spin :

stop on the road until you get the 'feel' and handling of the

machine thoroughly—even if you do keep your lunch waiting.”
You will then reduce to the minimum the time during which you
are a potential source of danger to yourself and all other road
users. Now for the first run. Don't forget the driving licence and
the insurance “certificate.”

Standing on the left-hand side of the machine, push it gently
off the stand with the engine still revving and the gear in neu­tral. The machine will undoubtedly, to the new rider, appear
at first rather unwieldy. Therefore, stand close up to your
mount when wheeling it about, otherwise you may find yourself
underneath the machine. Take things coolly, as though you

had driven all your life, and, sitting on the saddle, raise the

clutch and push the gear lever into first gear position. Then speed

up the engine slightly by opening the throttle and engage the
clutch by gently and slowly releasing the lever. You will then
move off. It is best not to place the feet on the rests just at first,

but to let them dangle on the road ready to support the machine
if you find balance difficult. But place them there as soon as you
feel able to do so. Bear in mind that you can stop the machine
instantly you are in difficulties by raising the exhaust lifter or
declutching, and applying the brakes. Never attempt to use any
of the gears without first declutching. The novice always gets the
impression that he is travelling very fast on first gear, and does

not at first feel equal to changing into “second.” Moreover, when

changing, he feels it imperative to look down at the gear quadrant

to verify the gear lever position. If the gears are fumbled,

instantly whip out the clutch and start afresh. It is advisable,

therefore, to travel some considerable distance on bottom gear,
and practise going back into “neutral” without stopping the
engine. After getting accustomed to driving on first gear, a
change should be made into “second” on a piece of road with no
cross-roads. Speed up the machine, and then throttle down, lift
the clutch, and push gear lever into position, afterwards letting
in clutch again. It is worth while, now you are getting “warmed
up,” to go a step further, and get into top gear by repeating the
former operations. Be careful not to allow the engine to “knock,”

which it will do if driven too slowly under load. “Knocking” is

intensely injurious to an engine, and is usually due to pre-ignition.

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THE FIRST RUN

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Therefore, open the throttle to speed the engine up, and slightly
retard the ignition temporarily. It is always advisable to ease

the clutch a little until the engine impulses become uniform and
smooth. Once in top gear, if will be found that riding is much
easier, and you will now begin to acquire considerable confidence.

The pleasant “zoom” of the exhaust seems very stimulating after

the comparative clatter and “fuss” that is noticeable when driving

on low gear. You will probably be tempted almost immediately
to open up a bit—even have a burst of speed. There is no harm
in this if the road is clear and straight ; but for heaven's sake don't
do it if there is a suspicion of an obstruction ahead. Also remem-

ber that you are driving a new engine (see page 46). When
slowing up, leave a good margin of safety. On changing
down, the machine should be slowed up until it is travelling at
a speed at which it normally does on the gear that is about to

be engaged, and the engine must be revved up slightly. The
two engaging pinions will then be running at the same speed.
No changes down should ever be made while travelling over

15 m.p.h.

This is about all that need be said regarding the first run. We

will conclude this chapter with some general hints on driving, and

a survey of the chief dangers of motor-cycling and legal matters.

HINTS ON DRIVING

Use of Gear-box and Clutch. This has been dealt with to some

extent in the foregoing paragraphs, and the remarks there should
be carefully borne in mind, and if carefully observed should enable
perfect gear changes to be made. A few additional remarks
regarding possible abuses of the gear-box and clutch that may
unknowingly be committed are added herewith—

Never employ a low gear for braking purposes; that is to say,
never engage a low gear when travelling fast in order to pull up,
and do not use a low gear when descending hills, unless they
are quite out of the ordinary, for the internal expanding type
brakes should be capable of fulfilling all requirements in this
direction.

The machine should also never be run unnecessarily on first
gear. This gear is only provided for ease of starting and climbing
steep gradients, or when negotiating very heavy traffic demanding
a very slow rate of progress. Using the first gear unnecessarily
simply means extra wear and tear, high petrol consumption, and
shortens the life of the engine and transmission.

Never slip the clutch as an alternative to gear changing. Pro­longed slipping under load will burn out the cork inserts. Mod­erate slipping on the level at low speed does no harm.

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Take care never to allow oil to find its way on to the clutch

plates.

Tyre Inflation. Tyres should always be pumped up to a definite

pressure by consulting a pressure gauge. On the Firestone tyres,

used on. all A.J.S. machines, Schrader valves are fitted, and a
Schrader pressure gauge is obtainable. The tyres must not be soft
or rolling will occur on corners and the covers will wear badly.
Soft tyres are also liable to creep and thereby cause damage to the
inner tubes. If, on the other hand, tyres are over-inflated, exces­sive vibration will result, with horrible discomfort to the driver.
Needless to say, the rear tyre usually requires more inflation than
the front one. Well inflated tyres have least skidding tendency,
and produce the minimum amount of wheel slip at speed. In the
case of the two lightweight models (T5, TB6) the 25 in x 3 in.
tyres should be inflated to the following pressures: front tyre,
15-16 lb.; rear tyre, 22-24 lb.

With the heavyweight machines (T6, T8, TB8, T9) shod with

26 in. x 3·25 in. tyres, recommended pressures are: front tyre,

solo, 15-16 lb ; single S.C., 15-16 lb. ; double S.C., 17-18 lb. Rear
tyre: solo, 18-20 lb.; single S.G., 20-22 lb.; double S.C., 24-26 lb.
Sidecar tyre: single S.C., 15-16 lb.; double S.C., 20-22 lb. The
above recommendations apply to average weight drivers. For
abnormal weight or carrying pillion passenger add 2 lb. to rear
tyre pressure only.

“Running-in” a New Engine. When an engine is assembled

the bearings are made as tight a fit as is reasonably possible.
Owing to the crystalline nature of metal, an extensive and
prolonged smooth rubbing will compress the bearing surfaces of
the metal together until they attain a glass-like uniformity and
hardness. During the process, of course, a certain amount of play
arises in the bearings—just sufficient for good running fits.
Thereafter wear is very slow. But imagine what will happen
if the bearings are straight away subjected to violent friction and
heat. Instead of the surfaces acquiring a glassy surface, they will
rapidly wear down and become scored or abraded, and continue
to be rather soft. Another important point to consider is the
fact that until there are good running fits throughout the engine,
oil will be unable to find its way about in any quantity over the

bearing surfaces, which in consequence will remain partially dry
if the engine is unduly worked, with the attendant danger of
seizure. Distortion through overheating is also liable to arise.

Distortion is of two kinds—temporary and permanent. If per­manent distortion of the valve seatings takes place, an engine
will never be fully efficient afterwards. All A.J.S. machines
are tested on the road at Plumstead before leaving the manu-

facturers; but as the mileage they do is not great, the rider

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should therefore restrain his desire to drive the engine hard until
at least 500 to 600 miles on the road have been covered.

Sparking Plugs. Always run with a decent plug in the “pot.”

There are many good plugs now available, such as the Lodge H.1.
A cheap plug causes loss of power and pre-ignition.

Keeping an Engine Cool. If an engine's tune is to be main-

tained, it is essential not to overheat it. In spite of plenty of
cylinder finning, all air cooled engines are liable to become over­heated. To prevent this the controls should be handled carefully.

Always drive with the air lever of the carburettor open as far
as possible, consistent with even running, and the spark lever well
advanced.

After climbing a stiff gradient, never open out on the other side ;
allow the engine to cool either by raising the exhaust lifter, or by
nearly closing the throttle and opening the air lever. The throttle
must not be completely closed, otherwise no cooling air enters
the cylinder and the oil is liable to be sucked into the combustion
chamber by the vacuum thereby created which, of course, accel­erates carbonization. Some of the bad effects of overheating
have already been mentioned.

Methods of Controlling Speed. Speed may normally be con­trolled in two ways—(1) driving on the throttle, (2) using the
exhaust lifter. The latter method is bad practice, and on the
O.H.V. models may cause bent exhaust valves, for if the exhaust
valve is held up while the throttle is left open enough to produce
a combustible mixture, it will be continually swept by a high
temperature flame. That this does happen is indicated by the
banging that usually occurs along the exhaust pipe and silencer
when this practice is adopted. Moreover, the use of the exhaust
valve lifter necessitates complete removal of fingers from the

throttle, which is in itself dangerous. Driving on the throttle

has many points in its favour. Closing the throttle exerts a
powerful braking effect, which can be used to advantage both

when driving on the level and descending hills. Indeed, the

really good driver seldom uses his brakes. He cultivates such
good judgment of speed and distance that he does not often

require them. An occasional jab of a brake is all that he needs.
A front brake must never be used suddenly ; a skid will probably
ensue. The rear brake should always be applied first.

Cruising Speed. Every machine has what, for want of a better

name, may be called its cruising speed. By this we mean the
speed at which the engine runs most sweetly. It usually lies
somewhere between 25 and 35 miles an hour. The rider should
find out what this speed is in the case of his own mount, and drive
most frequently at that speed. If a long life is desired of an engine
it should always be driven well within its maximum capacity,

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that is to say, on about ¾ throttle. In the case of most riders

there is not much danger of doing this owing to the winding
nature of the roads in this country. At 65 m.p.h. what appears

normally to be a straight road often becomes suddenly full of
nasty bends which have to be negotiated carefully. Nevertheless
it is easy to over-drive an engine in hilly districts. While on the
subject of speed we will deal with that so hotly-discussed problem,

“What is a safe speed ?” The answer to this question is, “A.
speed at which the driver has complete mastery over his mount
in the given circumstances.” In many cases the man with
leather helmet and. goggles hurtling along at 60 m.p.h. is far less

dangerous than the sublime idiot who leisurely careers over minor
cross-roads at speeds varying from 15 to 20 miles an hour. When
somebody on the main road nearly dispatches him and himself
to eternity (the best place for him), he miserably complains that

he was only doing 20 m.p.h.—20 m.p.h. across a main road I Such

people ought not to be charged with exceeding the speed limit,

but with attempted murder and suicide! The author has had the
misfortune to run up against one of these maniacs, and realizes

the nasty sensations that surge up when crashing broadside-on
into a vehicle, as well as the nasty repair bill that must inevit­ably follow. A theory has actually been advanced by some
motor-cyclists that it is safer to take cross-roads at high speed
because there is less time during which you may hit anything
coming across. This line of thought is analogous to that of the
Irishman who, when stopped for speeding, said that he was racing
to get home as quickly as possible because his brakes had failed,
and he was afraid of smashing into anything! Comment on this
illogical and suicidal reasoning is needless.

Cornering. The art of cornering takes some time to master.

We all know that for a bicycle or motor-cycle to get round a bend
fast without skidding it is necessary that the machine should be
banked, i.e. the rider must lean the machine inwards towards the
centre of the circle. The reason for this is as follows—every
moving body possesses momentum, and that momentum at any
given time acts in the direction that the body is moving at that
time. In the instance of a body describing a circle it is evident
that the body is continually changing its direction (a circle theor­etically consists of an infinite number of. straight lines), and

consequently the momentum acts tangentially. Thus there are

resultant forces continually urging the centre of gravity of the
motor-cycle outwards from the centre, when rounding a bend.
But this can be counteracted by inclining the body and machine
inwards. A better method, used by some fast drivers, is to in­cline the machine inwards and the body outwards. Using this
method, one may corner almost on the exhaust pipe. Make a habit

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of always cornering close in at the blindest part, and indicate

your intentions well before actually turning off at a sharp bend.
It is no consolation to be able to say that you gave a hand signal,
after a high-powered car has buckled up your rear wheel. Never

omit to sound the horn at all corners. Sometimes it pays to
swerve slightly to the offside before approaching a moderate

bend at high speed, throttle down, and bank inwards, thereby
cutting the corner somewhat and at the same time keeping close
in. The throttle may be opened up again half way round the
bend. This kind of cornering, however, comes under the heading

of “stunt” driving, which is not recommended to any but the
experienced driver.

When cornering with a pillion passenger for the first time,
reduce speed well below that at which you generally take a corner
solo. Failure to do this will probably cause you to drift well
away from your proper side of the road—a most risky procedure—

because you are afraid of banking too steeply. It is, undoubtedly,
unpleasant to bank steeply with a passenger riding pillion. We
will deal with pillion riding again later,

Left-hand corners demand special caution on the part of the
driver of a sidecar outfit, according to the speed at which corners
are taken. He should throw the weight of his body towards the

left. A passenger may assist the driver by leaning in towards the

centre of the bend; but he should not adopt “T.T.” acrobatic
methods. Your passenger might easily break his neck against a
lamp-post, to say nothing of the indignation and terror that
would be caused to any witnesses of the occurrence. The proper
manner to navigate a sidecar round a left-hand corner is as
follows: approach the corner at a pace well below that which
safety requires, and open the throttle gradually and cautiously
on the bend ; the outfit will then pivot on the sidecar wheel, which
is precisely what is required. Conversely, on a right-hand corner
either close the throttle or apply the brake a little as the outfit is
actually swinging round the bend ; it will then pivot on the rear
wheel of the motor-cycle. Always endeavour to take corners with
a sidecar at a reasonable speed, especially when turning to the
left, as centrifugal force puts a great lateral strain on the machine.
When turning to the right the lateral strain is reversed in direction
and has a crushing effect on the sidecar axle via the torque arms.
At high speed the strain is terrific, and a sidecar axle may break.
Result, an inquest. Difficulty is often experienced in the manage­ment of an empty sidecar while cornering. Ballast substituted
for the passenger is of great assistance in this connection.

Sidecar Alinement. If a sidecar outfit has a tendency to steer to
the right or left due to reasons other than road camber, the
motor-cycle is probably not upright or else the sidecar itself is

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(A)

(B)

(C)

(D)

(E)

(From " The Motor Cycle")

A = Signal to stop
B = Slowing down

C = Turning to right
D = Turning to left

E = Overtake me

FIG. 26. RECOGNIZED SIGNALS TO BE USED BY DRIVERS

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out of alinement (see page 151). After a new A.J.S. sidecar has

done a considerable mileage it occasionally happens that the side­car fittings take a permanent “set,” causing the machine to lean
slightly towards the sidecar. This trouble can be easily cured by
means of the adjustable arms.

Hill Climbing. There are few hills likely to be encountered by

A.J.S. riders which present any serious difficulties. It is purely
a question of making the best job of it, or in other words, a climb
that will not bring the blush of shame if there should happen to be

critical motor-cyclists watching hill ascents, as is often the case,

by the side of the road. It is advisable, before an ascent is made,

to allow the engine to cool down very thoroughly first. Unless
the road is notoriously bad, take a fast determined rush at the

hill, and get up as far as possible on top gear. But never allow
the engine to labour. As the machine slows up it will be necessary

to give less air and retard the ignition gradually. Change to a lower
gear instantly the revolutions fall seriously, and there is danger
of overstraining the engine. Do not race the engine on low gear,
for racing an engine takes more wear out of it than hundreds of
miles of normal usage. If a bad patch of road looms ahead which
will necessitate changing down again, change down before you
reach it. Choose your path carefully, and swing wide round all
corners that are not blind. It is preferable to drive at a good

speed on some bad surfaces. This also applies to driving on

“wavy” level roads. It will be found that periodic “plunging”
does not then occur. Sometimes speed variations will also pro-

duce the desired effect. Having made a hill ascent, allow the

engine to cool either by stopping it or by using the exhaust lifter

while descending the next hill.

When climbing a steep hill with a sidecar it is not necessary on
taking a left-hand bend to lean over in that direction, as the
natural sidecar side-drag tends to turn the machine to the left.
This does not apply with a right-hand bend.

When climbing a very steep gradient the passenger can assist
the driver by placing as much weight as possible over the rear
wheel. Similarly, on descending an unusually steep gradient, he
should try and put as much weight as possible on the driving
wheel so as to assist the steering.

Coasting. Running declutched down hill with engine stopped
is very popular among riders. It cannot be denied that the
smoothness and noiselessness of it is altogether a delightful
sensation. This procedure, however, unless the hill be very long,
does not lend itself o cooling the engine very well, and we must
assume that the driver has been climbing—unless, of course, his
garage is situated on the top of a hill. It is far better to use the
exhaust lifter or, if the hill is steep, to open the air lever and

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partially close the throttle. When letting in the clutch again, it
is desirable that it should not be let in under full compression
with the machine travelling fast; such action may result in a

bad skid, and damage the rear tyre. Wait until your mount has
slowed up to about 20 m.p.h. ; then raise the exhaust valve and
let the clutch in gently ; when the click and whirr of the valves
indicate that the engine is coupled up again, drop the exhaust

valve. The throttle being only slightly open, the power strokes
will be resumed gradually.

Engine Sprockets for Hill Climbs. For 3·49 h.p. models it is

useful to have spares with from 1.8 to 22 teeth. For 4·98 h.p.
machines suitable sprockets have 18 to 20 teeth. A. 19-tooth
sprocket suits the average hill, but 18 teeth gives more speed for
steepish gradients. As a rule, in a hill-climb it is better to gear
too low rather than too high. Experience is the best guide.

Pillion Riding. We will not enter into the question whether

pillion riding is dangerous or not. Undoubtedly much depends
upon the qualities of the driver and the circumstances under which
it is undertaken. The fact remains that, as the law stands at
present, the only legal requirements are that the pillion passenger
shall sit astride a suitable pillion seat fixed to the machine and
shall be covered by insurance. We will, therefore, give a few
hints which, if observed, will contribute to safety.

1. The pillion rider should sit astride as close to the driver
as possible, so as to put the minimum weight on the tail of
the machine. Preferably he, or she, should hold the driver
lightly by the waist, and sit on the machine as limply as

possible.

2. Footrests should always be provided for the passenger.
The feet cannot then foul any of the mechanism, or interfere
with the stability of the machine (see Fig. 27A).

3. The driver should not engage in protracted conversation
with his passenger while driving.

4. If the roads are greasy do not take a passenger on the back.
Crossing and recrossing greasy tramlines on top gear with a
passenger is a risky business. It is safer to engage a low gear,
and place the feet on the road.

5. Never swerve or bank violently, two-up. The passenger
may get terrified, and cause a disaster by leaning one way or
the other.

6. Never take a pillion passenger on a long distance night

run.

THE BOOK OF THE A.J.S.

GENERAL HINTS

1. Use the hooter as sparingly as possible. When essential,
deliver two or three quick imperious blasts, and be always

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prepared to stop abruptly. Sometimes it may be found essen-

tial to yell out to somebody rather than use the horn. The
language is usually highly coloured, but under such circum­stances politeness is criminal. Always use the horn at cross-

roads and corners.

2. Always give hand signals, even if you think you are alone
on the earth. If a habit is made of it, you will give them instinc­tively. Remember, however, to give signals in ample time.
When stopping, either put your right hand up, as shown in
Fig. 26, or move the left hand up and down vertically, as many
people do. In any case make your intentions clear. A signal
that is rarely used, but which is sometimes invaluable, is the
signal indicating that you intend to proceed straight ahead.
This should be given when you are confronted with oncoming
traffic which doubts your intentions at a cross-road. In any
doubtful situation, instantly whip out your hand to show what
you are going to do, and do it. Everybody knows the utter folly
of two people dodging each other. On the pavement two pedes­trians doing this invariably fail to clear each other, unless one
stops or gives way.

3. Never hesitate. Do the wrong thing rather than run
amok. You will then retain your nerve and keep your wits
about you.

4. If you should have to choose between killing someone
or risking death yourself, do not be a coward, but take the
risk. It is usually possible to slip backwards over the carrier
at the last moment.

5. Approach cross-roads dead slow.

6. Keep the eyes well ahead. By doing this it is often
possible to see over hedges traffic that is rapidly approaching.

The habit of taking a sweeping survey of the view ahead is
invaluable, and after a time becomes second nature.

7. Always remember that cows and sheep believe strongly

in obstruction.

8. Obey all special speed limits and notices (see Fig. 27) and

respect the white lines and automatic traffic signals.

By disregard of these you bring contempt upon motor-cyclists

as a body.

9. Never take things too fine. In ninety-nine cases out of a

hundred you will escape, but on the hundredth you may crash.

This particularly applies to “cutting in.”

10. When streets are greasy, give and take as much room as
possible. A side slip on the open road, at reasonable speed,
seldom does much harm; but a skid in front of a lorry means
either the hospital or the cemetery. Therefore, never behave
rashly in front of heavy vehicles.

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11. Always have a finger close to the throttle and a foot ready

for the brake.

12. Always ensure that the oil tank and gear-box contain

sufficient lubricating oil.

13. Keep the “certificate” in a safe place with the driving

licence on your person.

14. The speed limit has gone, but don't demonstrate the fact

too often in the wrong place.

15. If you have an electric lighting set look after the battery

and charge during the day.

ROAD DANGERS AND THEIR PREVENTION

Nowadays road dangers constitute a very real menace to life
and limb, but most of them can be effectively counteracted.
Some are unavoidable. Others are caused by the selfishness or
inexperience of the drivers themselves. The golden rule is this :
“Cultivate sufficient imagination to ride in a state of constantly
expecting the unexpected, especially over unfamiliar roads, and
always assume the other fellow may do the wrong thing.” Re­member that bad accidents always arise from, some unexpected
or sudden incident, e.g.—

A child suddenly darting across the highway.

Vehicles in front stopping suddenly (beware four-wheeled
brakes).

Cars you are overtaking drawing out.

A steam roller round the corner.

Cyclists riding abreast the other side of a canal bridge.
Faulty hand signals.
Sudden brake failure.
Snap of a throttle cable.
Attempted suicide by dogs, poultry, drunken men, old

ladies.

Skid of a vehicle in front.
Passengers dismounting from tramcars.
Pedestrian stepping off the kerb with eyes skywards.
Person emerging from behind stationary vehicle.

There are a thousand and one other contingencies that the
mind can conjure up, any or all of which may arise in lightning
fashion. It therefore behoves the motor-cyclist to concentrate
on his job, and never to allow either his mind or his eyes to wander.

When driving in traffic, a glance to ascertain whether any blue
smoke is issuing from the exhaust may easily cost a man his life.
Absent-mindedness in the professor's study is said to be a sign
of genius, but on the road it is a sure passport to eternity.

“Dangerous” and “Careless” Driving. Although the general

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20 m.p.h. speed limit, honoured more in the breach than the

observance, has now disappeared, a vigilant police watch on

driving is kept by the new mobile police force, and woe to the

motor-cyclist or motorist caught driving to the public danger.

“Dangerous driving,” now heavily punished, means driving at a
speed or manner dangerous having regard to all the circumstances

actual or hypothetical, i.e. having regard to other traffic or

pedestrians that are in the vicinity or might reasonably be

expected to be there.

In order to meet cases of negligent driving of an unpremeditated
nature, such as failure to give hand signals, “careless driving” is
made an offence with which a motorist may be charged, and the
penalties for this are not quite so severe as for "dangerous driv­ing." Passing on corners and cutting-in would come under the

first heading, however. “Drunk in charge” usually means im-

prisonment and automatic suspension of the driving licence. A
summons must be served within fourteen days of an alleged
offence, and the driver must be notified at the time of committing
it that prosecution will be considered.

Danger Signs. There are various types of signs scattered about

the country, and they should be implicitly obeyed. Fig. 27 shows
the principal types. Those shown at A from top to bottom are
respectively the local speed-limit sign, one indicating that road
traffic is prohibited, and a general motor notice. At C and D are

a group of self-explanatory signs. In spite of the abolition of the

general speed limit, some local limits still exist and must be strictly
observed. A special sign designed to show when a driver is
approaching a main road from a subsidiary road is now in com­mon use. This sign is shown at B (Fig. 27).

Skidding. Nerve is the best antidote to skidding. A bold
rider seldom skids, and when he does he usually corrects it,
Skids seldom occur on dry roads. Too violent braking or cross­ing tramlines in a timid fashion is usually the cause. Brakes
should be very gingerly applied on wet roads, and tramlines
should be negotiated fearlessly at a good speed and at a sharp
angle. A rear tyre with worn tread usually facilitates skidding.
Therefore, during the winter months, if the rear tyre is worn
badly, change it over to the front. This procedure is recom­mended, anyway; for it enables the best tyre mileage to be
obtained. If a skid does occur, instantly declutch and turn the
machine in the direction of the skid, braking at the same time.
If you do not go over, carry straight on without stopping.

Animals on the Road. Animals that the motor-cyclist en­counters on the road vary from small Pekingese dogs, complete
with pink ribbons, to vicious-looking bulls. The former may be
completely ignored, but the latter must be treated very cautiously.

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If a fierce terrier, or an Alsatian wolfhound, leaps at you, it is

safer to deal severely with it, rather than say, “Good dog,” or
something to that effect. By this we mean throttle up and either

kick out or land out with a clenched fist. This action is unlikely
to harm the dog, but the suddenness of it will momentarily deter
it from its canine instincts and will enable you to accelerate clear.
A dog jumping about under the front wheel is decidedly dangerous
and do not be afraid of accelerating. A dog can always get clear

THE BOOK OF THE A.J.S.

A

FIG. 27. SOME IMPORTANT ROAD SIGNS

of a single track motor-cycle, but not a car. A car driver should
always slow down. Straying cattle are sometimes encountered on
country roads at night, and the rider should be prepared to meet

with unlighted objects accordingly.

Always throttle right down when passing horses. If you are
signalled to stop and fail to do it you are violating the law. Apart

from this, a horse is a very faithful and intelligent animal, and
you have no right to frighten it by roaring past. Such action is
contemptible.

Dazzle. When driving by night, cars with glaring headlights

are frequently met. If the eyes are allowed to face such lights,
the pupils contract to such an extent that temporary blind-

ness ensues immediately after the lights have passed. This
is very dangerous if there is any traffic immediately ahead of
you. Make it a rule to keep the eyes focused on the ground
in front, and “concentrate” them at the moment of pass­ing. This should entirely eliminate what is usually called

“dazzle.” It is purely a question of using a certain amount of

will power and common sense. On a model provided with Lucas

B

C

(From “Road Sense,” 1930)

D

DRIVING HINTS AND TIPS

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electric lighting always dim the headlamp when approaching
a brightly illuminated vehicle. Its driver, if he is a gentleman,
will then cut out the glare from his lamp or lamps.

When a fog is coming on before dark, it is imperative not
to waste a second during daylight if bound on a long run
with little prospect of “getting there” by any other means.
There are three reasons for this—(1) As soon as the ground
temperature falls on the approach of night, the fog will rapidly

thicken, (2) lights in fog are worse than useless for picking out one's

way, (3) the fog will drive most road users off the road, and there

will be little likelihood of any assistance forthcoming, should you
have any trouble. If engine trouble should develop just before

dusk, you will have to do one of two things—either work like a
Trojan and get the engine running again, or abandon all attempts
to proceed farther. Driving long distances in thick fog requires

all the courage and nerve that you can summon up. If a vehicle
ahead is making good progress, follow its tail light. It is aston­ishing how a man can steer his machine dead straight, so long as
he has a sense of direction, even though he may be unable to see
the road at all. In some cases frost-covered telegraph wires show

up above a low lying fog and give considerable assistance. Sim­ilarly tramlines are very useful. A dense fog is often accompanied
by icebound roads. Driving on an icebound and fogbound road
by night is not one of the best forms of amusement. Skilful use
of the throttle has to be made to eliminate wheel spin, and brakes
have to be used super-cautiously. Driving in fog, in spite of its
dangers, has attractions to some people. It undoubtedly tests
to the utmost the driver's abilities and endurance.

57

GENERAL REMARKS

Obey the law not only in letter but in spirit, and be courteous

to all other road users. Never pass by a stranded motor-cyclist

without asking whether you cannot assist. Nothing fills a rider

with such disgust as for men to roar past when it is obvious that
the driver requires help. It may be only a special size spanner
that he requires, but stop to inquire. Remember, the modern

motor-cycle is a ghastly thing to push up hills. Troubles that may

beset the rider are many, but, actually, troubles are few and far

between. All possible troubles are fully dealt with in Chapter VI.

After considerable experience on the road the driver can tell by

the sound and behaviour of his engine whether it is running as it
should, and can diagnose trouble instantly it occurs. In fact,
the machine becomes an open book to him, and he never lets the

idea of getting stranded enter his head ; also he feels confident
of rectifying any trouble that may occur. Every engine has a

5—{5301A)

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personality of its own which only the driver who has studied if
understands, and it will only give of its best to this driver.

Road Accidents. To conclude these hints, the author feels he

must emphasize the very real need for the cultivation of driving
skill and road sense among all motor-cyclists. Statistics of road
accidents for the past year, recently issued by the Ministry of

Transport, and which the author has before him as he writes these
words, make appalling reading. No less than 6,500 people met
their deaths on the road in 1931—an average of eighteen per day.
Altogether there were about 200,000 accidents known to the

police as compared with 40,000 in 1918. Thus in thirteen years road
accidents have become five times as frequent. The proportion of

motor-cycle accidents does, however, show in a favourable light.
Something must be done to stop this wanton destruction and
maiming of human beings ! It is your bounden duty as an A.J.S.
motor-cyclist to see that you do not contribute to the list of killed
and injured on the roads of Great Britain during the forthcoming
years, when motorists and motor-cyclists will become more and

more numerous.

The legal matters regarding licensing and registration having
been disposed of it remains to deal with questions concerning
breakage of the law. It is wise to remember that in all
cases of accidents or of legal trouble the legal departments of
the Automobile Association and other road organizations are

always ready to assist members on receipt of an S.O.S., and to
give free legal defence in the case of certain offences. The follow­ing information is given because in law “ignorance is no defence.”

What to do in Case of Accident. The first thing to do in case of

accident is to obtain the names and addresses of at least two
independent witnesses who are likely to assist your case. Carefully
jot down on paper all particulars of road width, place of accident,

your speed at time of accident, whether horn was sounded, and
all other particulars relating to the accident. Remember that
insurance companies rely mainly upon the police reports. There-

fore, it is essential to summon a police officer so that he can take

down signed statements from both parties, both for perusal by
police headquarters and for the benefit of the insurance companies

concerned. A full truthful statement must be made. Anything

withheld will react unfavourably against the driver later on. If

an injured person is likely to make a claim, an independent medi-

cal man should be called to examine him and make a report. Do

not engage in any correspondence without legal advice, or if this

is not taken, make clear that all your statements in the letter are

made without prejudice to your case; and refrain from making

THE BOOK OF THE A.J.S.

SOME POINTS ABOUT THE LAW

DRIVING HINTS AND TIPS

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statements either at the time of accident or afterwards, which
might be construed as admission of liability. Never offer money
to the injured person, for motives of sympathy arc often construed
into admissions of legal liability.

Name and Address. To anyone who complains that the motor-

ist has committed an offence of driving to the common danger,
the driver must give his name and address. The maximum
penalty for refusing, or for giving a false name and address, is
£20, with heavier penalties for subsequent offences.

The Order to Stop. A person in charge of a horse may order a

motor-cyclist to stop, and so may a constable in uniform, or a man
injured by your machine. To fail to do so is an offence. In any
case an order to stop should never be ignored. The signal to
stop should be made as already noted on page 50.

Endorsement of Licence. Convictions under the Road Traffic

Act, 1930, may be endorsed on the back of the licence, except a

conviction for obstruction. In the case of “dangerous driving”

(page 55) an endorsement automatically follows. It is not widely
known that a driver who has had his licence endorsed can obtain

a clean licence at any time for the fee of 5s., provided that he has

not, during a continuous period of not less than three years, had
any conviction endorsed.

Drunkenness. A person found in charge of a motor-cycle while

under the influence of drink is liable to imprisonment without the
option of a fine, and on conviction his licence is automatically
suspended.

Warning of Approach. It is compulsory to give audible warn-

ing of approach whenever it is necessary. Failure to do so

renders the driver liable to conviction for “dangerous driving,”

and to an action for negligence if anybody is injured as a result.

Exhaust Cut-out. It is illegal to use an exhaust cut-out, or

any contrivance enabling the exhaust gases to escape into the
atmosphere without first passing through an effective silencer.

Arrest. The driver is liable to arrest by a police constable

(whether in uniform or not) if he refuses to give his name and
address, refuses to produce his licence on demand, or if his machine
does not bear the identification (registration) marks.

Rules Regarding Number Plates. The driver of a motor-cycle

is guilty of an offence if the number plates are not properly fixed,
or if they are in any way obscured or rendered illegible or not
properly illuminated, unless he can prove that he has taken
reasonable steps to prevent this, and if the driver is not the owner
the latter may be charged with aiding and abetting.

Illumination (see also Chapter II). The driver must always

comply with the existing lighting regulations; otherwise he may

be summoned. One number plate must be properly illuminated

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Regarding the Registration Book. When a licence is issued a

registration book is issued to the owner, and this must be sent to

the Council with whom the vehicle is registered as follows—

1. When any alteration is made to the vehicle.

2. On sale or change of ownership.

3. On change of address.

4. When vehicle is broken up, destroyed, or permanently sent

out of the United Kingdom.

Obstruction. The machine must not be left for an unreasonable

or unnecessary time on the highway in such a position that it
constitutes an obstruction to other traffic or pedestrians.

Time Limit for Summons. Unless previously warned at the

time the offence is committed, notice of an intending prosecution
for committing any motor-cycling offence must be given to the
driver or the registered owner of the motor-cycle within 21 days

of the alleged offence.

Right of Appeal. A person convicted of an offence under the

Road Traffic Act, 1930, has the right to appeal to next Court of
General Quarter Sessions. A right of appeal lies against an order

disqualifying any person from obtaining a driver's licence.

Speed Limit. Although general speed limit has been abolished,

special limits of 8 or 10 miles per hour are fixed in certain towns
and villages. These must still be strictly observed.

Leaving the Machine. A motor-cycle may not be left with the

engine running while the owner is absent, however short the

period.

Police Warnings. A new system of dealing with first offences

of a minor nature has recently been introduced. Under this
system it is customary, unless the offence be serious, to give the
offender an official warning instead of bringing a prosecution.
Whether or not the offender be prosecuted is left to the discretion
of the Commissioner of Police. This system is a step in the right
direction and does much to avoid frivolous prosecutions.

Petrol Storage. Those who desire to possess a petrol “dump”

on their own property should remember that a maximum of
60 gallons in 2-gallon tins is permissible, and it must be located

at least 20 ft. from an occupied building. Also the store must
be arranged such that, in the event of fire and leakage from the
tins, the inflammable liquid will not escape. Suitable ventilation
must be provided, and when any petrol is kept other than in the
fuel tank, a fire extinguisher or sand must be kept on the premises.

THE BOOK OF THE A.J.S.

CHAPTER IV

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RUNNING COSTS AND TOURING

IN this chapter we will consider briefly the expenses connected
with motor-cycling, and thereafter we will discuss some matters
relating to touring. Most motor-cyclists, sooner or later, have a
desire to extend their field of activities. They become tired of

constantly wandering over their old routes, which are usually

confined to a radius of about 50 miles from their homes, and they
wish to set out on a long distance tour, either in this country or
abroad. For the present let us deal with running costs.

RUNNING COSTS

Cost of the Machine. This is the principal cost of motor-cycling,

representing as it does an initial outlay of some £50 or more,
according to the type of machine purchased. But remember
this is really an investment, and the expended capital can be
recovered minus a certain sum representing depreciation on selling

the machine. Any A.J.S. model can also be bought on the hire­purchase system.

Depreciation. This ugly item is an added reason for purchasing

a reputable machine in the first place, for such machines always
command a fair market price. It is a hideous fact, but neverthe­less true, that the purchaser loses at least £5 in removing the
machine from the shop window. From that time onwards the
machine can no longer be regarded as new. It stands to reason

that depreciation* depends mainly on the way the machine is
kept, but it also depends largely upon the age of the machine.

Many people will not buy a machine that is more than three or

four years old (old in the sense of date of design). Therefore,

unless the rider intends to stick to the machine until it is thor-

oughly worn out, it usually pays to sell after a couple of years'
riding. The vendor may then reasonably hope to recover at
least 50 per cent of his capital expenditure. If the machine is in
sound condition, and the appearance is still good, he may get

back as much as 70 per cent. In reckoning the cost of motor-

cycling, this factor must be taken into consideration. Reckless
or careless driving and general neglect of the machine cause

depreciation to be very rapid, and motor-cycling becomes a
costly affair.

Cost of Licences. This has been already dealt with in Chapter

Depreciation is usually reckoned at 331/3- per cent per annum.

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II. It represents a very fair outlay to the motor-cyclist, and is
rather disproportionate to the damage done to the highways.
However, under the present system of taxation, it must be faced
cheerfully.

Garaging. Keeping a solo motor-cycle at a public garage costs

about 2s. 6d. a week on the average, or £6 a year, and a combina­tion an extra shilling a week. If circumstances permit, it is well
worth while erecting a cheap shed or buying a portable and
collapsible shed ready-made. Overhauls can then be carried out
in perfect seclusion and, moreover, no objection can be made to
coming in at " unearthly hours." Such a shed should not cost
more than £4 or £5, and, of course, it will last indefinitely. Due
regard must be paid to fire regulations (see page 60), and before
erection, plans of the structure must be submitted to the local
surveyor for approval.

Petrol Consumption. Petrol consumption depends on many

factors. Fast driving or driving on low gears results in a high

consumption. Also a badly tuned carburettor will not contribute
to fuel economy. Speaking generally, however, the average 3·49
h.p. machine should have a fuel consumption of at least 80 m.p.g.,
and when specially tuned should do about 90 to 95 miles on a
gallon of spirit. A 4·98 h.p. machine should do at least 70 m.p.g.
solo, and at least 50 m.p.g. with sidecar.

Oil Consumption. One quart of oil should suffice for a mileage

of at least 500, with considerate driving of a 3·49 h.p. solo machine

and at least 350 for a 4·98 h.p. model.

Tyres. Tyres, when well inflated, should have a useful life of

from 10,000-12,000 miles. A certain amount of luck enters into
the question, for a severe gash due to a piece of broken glass may

practically ruin a new tyre, but this rarely happens. Some words
on tyre maintenance are given in Chapter III (see page 46). When
buying new tyres it always pays to get the best, and nothing but
the best. Firestone tyres are standard on all A.J.S. machines.

Sparking Plugs. Quality here again is important. Cheap

plugs give poor service, and soon want renewal. Buy plugs as

recommended by the makers (see page 47). These should only

need annual renewal. Unsatisfactory plugs often cause mysterious

loss of power.

THE BOOK OF THE A.J.S.

TOURING

Dress. Long distance touring requires careful preliminary

consideration regarding dress if any enjoyment is to be derived
from the tour—or rather if acute discomfort is to be avoided.
The all-weather motor-cyclist has to cope with every variety of

heat and cold, wind and wet. For short distance runs dress
does not matter much. All that is required is protection of the

RUNNING COSTS AND TOURING

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clothes and eyes from dirt. Clothing for this work is left to the
rider's fancy. Some go about clad in flying suits, helmet, and
so on. Others go about dressed in riding breeches, leggings, and
a bright coloured beret. All this is a question of individual taste,
but where touring is concerned, the rider must have plenty of

warm waterproof clothing and goggles should be worn. Con­stant and prolonged exposure of the eyes to cold and dust pro­duces chronic inflammation, and is thoroughly bad for the eyes.

All-Weather Riding. Whilst it cannot be denied that riding

in spring and summer weather is very pleasant, winter riding has
its charms. Many riders openly avow that they do not care
what the weather is like. They get plenty of satisfaction under
all conditions. This is, perhaps, true in the case of a certain class
of rider, but not for the majority. This type of motor-cyclist
keeps himself warm through sheer excitement, not woolly under-

clothing ! However, we will deal with the average rider, who

places bodily warmth foremost.

The commonest type of winter dress consists of the ordinary

buff waterproof coat and leggings, the latter either buttoning up

the sides, or lacing. Most accessory dealers sell this type of
apparel. They are, however, rather clumsy, and apt to get torn
and become generally dilapidated looking. A far more satis­factory garment is one of the surplus R.A.F. Sidcot flying suits
with fur collar, that can be obtained for the modest sum of about
three guineas. Better still, get a leather coat and trousers to

match. No definite instructions regarding apparel can be given.

It is all a question of taste and money available.

Headgear. A tight-fitting cap is the most suitable headgear for

normal motor-cycling purposes. If predisposed to blow off, it
may be reversed, that is, placed peak to the rear. Many riders
are inclined to dispense with headgear altogether. This is all right
provided that the hair is not liberally swamped with hair grease.
In this case dust and grit accumulate horribly. For long distance

touring, in cold weather, the helmet is unchallenged ; it keeps the
ears and face warm and free from road dust. For competition
riding (reliability trials excluded!) the crash helmet is essential.

In all track racing it is compulsory to wear such a helmet.

Gloves. The problem of keeping the hands warm and at the

same time enabling them to finger the controls sensitively is a
difficult one. Many fast riders prefer to do without gloves, saying
that they would rather have the finger tips cold than run the risk
of being cold all over. Woollen gloves are dangerous, as they may
open the throttle by catching on the lever when removing the
hand to change gear. Gauntlets keep out the cold, but spoil the
sensitiveness of control. An attempt to solve the glove difficulty
has been made by several firms who market a rubber muff which

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fits over the handlebar grip and controls. This idea is very sound,

and should the rider experience great discomfort through cold
hands he cannot do better than obtain a pair of these muffs.

Preparing for a Tour. If the reader is contemplating an exten-

sive tour, and is a member of one of the Associations mentioned

in Chapter II, he should write to the secretary of the Association
concerned and apprise him of the intended route. A detailed
itinerary will then be supplied, and useful information concerning
state of roads, etc., given. When undertaking a Continental
tour, the society, if requested to do so, will obtain the member's
passports, carnets, or triptiques, and thereby eliminate the
necessity for leaving deposits when visiting a foreign country.

Maps and Guides. These are very necessary adjuncts to tour-

ing, and indeed the fascination of planning a tour is part of its
pleasure. The route should be traced out in red ink on the map
to facilitate reading. Large scale Ordnance Survey maps are
the best, as they show all contours, and the route may be chosen
so as to avoid all the worst gradients, unless the tourist wishes
to include all the fine view points, and then, of course, he will
select the hilly roads. The tourist, if his time is limited, should
split up the route into sections, allotting so much time for each
section. He can then run to a definite time schedule. For long

distance touring in the United Kingdom, the Michelin guide is of
great value, giving as it does all particulars regarding hotels­repairers, and other useful information.

Spares. There is little need to carry more than a repair outfit.

pump, complete tool kit, spare plugs, spare tubes, spare chains and

links, one spare valve complete with spring, washer, and cotter.
and a complete repair outfit for tyres, as before mentioned. Pack

the tools tightly with rags. Also take some spare bulbs.

Luggage. For touring purposes, it is obviously senseless to

burden up the machine with luggage. Carry on the machine the

absolute minimum amount necessary. Send the rest by rail.

We will not defile these pages with a description of all the gear and
tackle necessary to keep man in a civilized and respectable condi­tion. We will leave that to the reader's common sense.

Taking the Machine Abroad. The triptique, referred to pre-

viously, enables the owner to travel in Finland, France, Italy,
Holland, Belgium, Romania, Spain, Portugal, Russia, Norway,
and Sweden, or as an alternative a member may get an Inter-

national Customs Pass, issued by the A.C.U. and A.A. to members
and non-members, whereby the highest continental duty payable

suffices for all the countries forming part of the convention.

International Travelling Passes (duration, 12 months) are also

issued, enabling the holder to travel in all countries which are

parties to the agreement, without obtaining the special licences

THE BOOK OF THE A.J.S.

RUNNING COSTS AND TOURING

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or carrying special numbers in each country as hitherto. The
Customs Pass concerns the customs duty payable ; the Travelling

Pass is exclusively a licence for the machine and driver abroad.

It is no longer necessary for the tourist to be examined by a
foreign official, to obtain foreign licences, or to undergo any other
formalities. It is only necessary to obtain the International Pass
and fix an oval plate to the machine with the letter G.B. painted
in white on a black background. This plate must be illuminated

by night.

Continental Rule of the Road, etc. As a general rule Keep to

the Left and Pass on the Bight in Austria, Hungary, Portugal, and

Sweden.

As a general rule Keep to the Right and Pass on the Left in
Belgium, France, Germany, Holland, Italy, Russia, Spain.
Switzerland, and the following provinces of Austria and Hungary,
viz., Carniola, Dalmatia, Tyrol, Istria, Carinthia.

The speed limit in Belgium is 40 kilom. an hour in the country
and 15 in town. Special regulations apply to Brussels. Most
Belgian roads are very bad.

Lighting-up time in Prance is 15 minutes after sunset. Hear
number plates must be illuminated. French roads are, on the
whole, good. Cars and motor-cycles entering Paris are stopped,
the petrol in tanks measured, and octroi duty charged.

The roads in Holland are generally good, but narrow and
winding. No special limit is fixed on country roads, but motorists
can be prosecuted for driving to the common danger. Some
roads are closed to motor traffic.

The general rule of the road in Italy is to keep to the right, but
it is frequently reversed in many districts and towns.

In Northern Italy and parts of Central Italy the roads are good
and often excellent. In the Southern Provinces the roads are bad.

The speed limit in Spain is under 20 m.p.h. in parts.

65

GENERAL HINTS ON TOURING

A few general hints on the subject of touring may well conclude
this chapter and, if acted upon, will contribute to the pleasure
derived by the tourist—

1. Before setting out on a long distance tour satisfy yourself
that the machine is in sound mechanical condition and that the
tyres, which can mar or make a tour, are likewise in good
condition.

2. See that you have aboard a complete tool kit and repair
outfit and a few vital spare parts.

3. If you are driving a combination, put a passenger in the

“chair.”

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THE BOOK OF THE A.J.S.

4. When touring abroad remember that you are the foreigner,

not those with whom you come in contact.

5. Never drive further in a day than you feel fit for, and keep
the speed for the greater part at 25-35 m.p.h. Such a speed is
not conducive to physical fatigue and enables you to see the
country through which you are passing.

6. Avoid the big towns and cities as much as possible.

7. Plan the whole tour carefully before setting out.

8. See that you are fully insured against accident, and against

third party risks and have the necessary "certificate."

9. Smear potato juice on goggles in wet weather to prevent

blurring.

FIG. 27A. A USEFUL ACCESSORY: A.J.S. PILLION FOOTRESTS,

An oval plate is used, the distinguishing marks of the country of origin, consist-

ing of one or two letters, painted in black upon a white ground.
A

Austria

B

Belgium

BG

Bulgaria

CH

Switzerland

CS

Czechoslovakia

D

Germany

ADJUSTABLE FOR ANY POSITION

INTERNATIONAL MARKS

F

France

GB

Gt. Britain & Ireland

GR

Greece

H

Hungary-

I

Italy

E

Spain

NL
P
R
RM
S

US

The Netherlands
Portugal

Russia
Romania
Sweden

U.S.A

CHAPTER V

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HOW THE ENGINE WORKS

IN these days, when the internal combustion engine is of such

vast service in so many spheres of locomotion—when it provides
the motive power for airways that are rapidly spreading through­out the world, when it is mechanicalizing great armies, and when
it is giving millions of people the facilities for enjoying healthy
recreation in the way of motoring, yachting, and other sports—
there are, perhaps, few people who have no glimmering as to how
the four-stroke internal combustion engine works. Nevertheless.
in a book primarily designed to meet the needs of the novice, a
brief explanation of the behaviour of the four-stroke cycle engine
can scarcely be omitted.

During the titanic struggle in Europe, which waged incessantly
from 1914 to 1918, the petrol engine progressed by leaps and
bounds. This was brought about through dire necessity. The
belligerent which had the mastery of the air was at liberty to
bomb and photograph every part of the enemy's lines, and to
wreak havoc and destruction miles in their rear. Thus the
frantic race for supremacy in engine design went on year after
year, for the performance of aeroplanes depends largely upon the
weight/horse-power ratios of the engines installed. But the
fundamental principle upon which the four-stroke engine works
has not altered one iota, and probably never will. True it is that
wonderful inventions are made from time to time—take, for
example, the Constantinesco Torque Convertor—but basic prin­ciples remain unaltered. Those who have some knowledge of the
“Otto,” or “four-cycle” stationary gas or oil engine, start with
a considerable advantage in the study of the petrol motor, because

the principles involved are identical in each case, although the

mechanical differences are very great.

THE FOUR-STROKE ENGINE

Coal gas and several other gases become explosive when mixed
with certain percentages of air (or oxygen), the percentage varying
with the particular gas used, and, to a lesser extent, with the
character and temperature of the atmosphere, so that a certain
gaseous mixture imprisoned in a space (called the combustion
chamber) will, if ignited, exert a pressure in all directions due to
the rapid rise of temperature on combustion ; and here it is well
to impress upon the reader the fact that all internal combustion

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motors are heat engines, i.e. they derive their power from the

intensely rapid production of heat at the moment of explosion ;
and it should further be noted that the more rapid the ignition,
and the more complete the combustion, the greater will be the

power of explosion- Strictly speaking (turning to the ridiculous),
an H.E. bomb is a heat engine—an engine capable of vast
destruction, including itself! To effect complete combustion it is
essential that the mixture is correct. In the case of the petrol
engine, a good explosive mixture contains by weight about 93
per cent of air and 7 per cent of petrol. Any variations from
this proportion will result in the combustion being incomplete,
or slow. In the latter case the mixture will burn rather than
explode—after all, the only difference between burning and ex­ploding is that intensely rapid burning generates great heat in
an infinitesimally small period, with the result that a loud bang
(called an explosion) occurs when the hot exhaust gases come up
against the atmosphere. The importance of having complete
combustion will be seen later. Incomplete combustion neces­sarily entails a considerable loss of power.

A crude illustration of the basis of gas engine or petrol motor
construction may be given if a coffee canister with tight-fitting
lid be imagined to be filled with the explosive mixture, and by
some means the contents ignited ; the result would be that, the
pressure in all directions being equal, a violent explosion would
hurl the lid far away; but if for that loose lid we substitute the
piston A, Fig. 28, a close sliding fit in a fixed cylinder B, the
piston being directly coupled to a crank C, by a connecting rod
D, the shaft E, on which the crank is fitted, will now have
reciprocatory movement of the piston transformed into rotary
movement of the shaft, and, at the moment of explosion, the shaft
will begin to rotate. Suppose the shaft E is attached to a
wheel F called the flywheel; then this wheel will be set in rota­tion also. Being purposely made heavy, it will go on spinning

for some time—in fact, if there were no friction it would go on
for ever—owing to the kinetic energy it derives from the initial
explosion by virtue of its inertia, and will cause the piston to

reciprocate in the cylinder. It can clearly be seen that the piston

makes two strokes for every revolution of the flywheel. Let us
assume that the explosion has just occurred, and that the piston
after reaching the bottom of its stroke, is ascending again. Imag­ine a valve at the top of the cylinder to be open during this stroke.
Then the products of combustion will be swept out of the cylinder
Similarly it is easy to see that, if on the commencement of another

down stroke, a second valve opens admitting an explosive mix­ture, while the first valve closes, the cylinder can be recharged
with gas during this down stroke. If, on again reaching the bottom

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of its stroke, both valves close, the charge of gas will be trapped
and compressed during the ensuing upward stroke ready for the
next explosion. Thus, clearly, the flywheel can be made to rotate
continuously, so long as provision is made for supplying the
explosive mixture and causing a spark to take place at the right
time. The explosive mixture is supplied by what we call a

69

FIG. 28. DIAGRAM ILLUSTRATING HOW A PISTON (4), SLIDING IN A

carburettor, and the spark by a magneto. We will for the present
confine ourselves to a more detailed description of the four-stroke
cycle. Let us refer to Fig. 29, which illustrates the cycle of

operations very clearly.

Two valves are fitted in the cylinder head, namely, the inlet

valve and the exhaust valve. When both these valves are closed

upon their seatings, the space above the piston is a sealed chamber.

CYLINDER (B), ROTATES THE FLYWHEEL (F)

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If the inlet valve is open, the cylinder is in communication through

the induction pipe with the carburettor. If the exhaust valve is

(1) Induction. (2) Compression.

(3) Firing (4) Exhaust.

FIG. 29. THE PRINCIPLE OF THE FOUR-STROKE ENGINE

open, the cylinder is in communication through the exhaust pipe

with the silencer.

We will now suppose that the piston has just reached the top

of its stroke after sweeping out through the open exhaust valve

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the hot gases left in the cylinder after a, firing stroke. During
this upward stroke the inlet valve has, of course, remained closed,
for otherwise the hot gases would have had access to the car­burettor via the inlet valve, with dire consequences that may be
left to the imagination. The two valves are open and closed at

the correct moments by cams upon the half-time shafts driven by

gearing off the engine shaft at half engine
speed. Fig. 30 illustrates how a valve
tappet A is operated by a cam B, with

rocker C, on a half-time shaft D, driven

by a gear wheel E, off the engine pinion

F. See also Fig. 54.

As the piston reaches the top of its
“sweeping-out,” or exhaust stroke, the
exhaust valve closes, and a moment
afterwards the inlet valve opens. This
is the point from which we shall assume

our four-stroke cycle to begin, and we

shall consider exactly what happens dur-

ing the four strokes which take place
before we arrive back to the starting
point and begin a fresh cycle. The four
strokes are called the induction stroke,

the compression stroke, the firing stroke,

and the exhaust stroke.

1. Induction Stroke. The exhaust valve

has now closed, and the inlet valve has
opened. The downwardly moving piston
has to fill the space behind it with air.

This produces an intense draught or
suction through the induction pipe and
carburettor. The blast of air sweeping
over the small aperture, or “jet,” to
which a supply of petrol is constantly
fed, causes a fine jet of petrol to rise
like a fountain in the carburettor. The fountain resolves
itself into spray, or is “atomized,” and the “mixture,” con­sisting as it were of air converted into a fog by the tiny petrol
particles, passes along the induction pipe into the cylinder. If
the induction pipe is warm the fog may, of course, evaporate
before it reaches the cylinder, a true mixture of air with the petrol
vapour being then supplied. In any case the fog will be evap­orated by the warmth within the cylinder itself. At the end of
the downward stroke of the piston the inlet valve closes, and
the cylinder becomes a sealed chamber containing the explosive
mixture.

FIG. 30. VALVE CAM

ACTION

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2. Compression Stroke. The crank on the engine shaft, assisted

by the flywheels, passes over its dead point, and the piston com­mences its upward stroke. The well-fitting piston rings prevent
the escape of the mixture on charge into the crankcase chambers,
and the charge undergoes compression. The amount of com­pression effected during the stroke depends, of course, upon the
design of the engine, that is to say, upon the relative volume of
the whole cylinder when the piston is at the bottom of its stroke
to the space left above the piston when it has reached the top of
its stroke. This is called the compression ratio. Gases, as we
all know, are heated by compression, and consequently, if a gas
is quickly compressed to, say, one-fifth of its original volume, its
pressure is increased considerably more than five times. As a
result, the pressure at the end of the compression stroke in an
engine having a 5 : 1 compression ratio is well over one hundred
pounds to the square inch.

3. Firing Stroke. We have now reached the moment at which

the charge is to be fired. The inlet and exhaust valves are closed,
the charge is fully compressed, and all is ready for the explosion.
This, of course, is brought about by the properly timed passage
of an electric spark between the electrodes, or points, of the spark­ing plug. It might be supposed that this spark should occur
just as the piston reaches the top of its compression stroke. This,
however, is not the case. The correct time for the spark depends
upon the speed at which the engine is running. The reason for

this is clear when we consider that no explosion—not even the

explosion of cordite in the breech of a howitzer—is absolutely

instantaneous. In the case of an explosive mixture of air and

petrol vapour, the explosion takes quite an appreciable time, and

there is a lag, so to speak, between the passage of the spark and

the moment when the exploded charge reaches its maximum
temperature and pressure. If, therefore, the engine is running
fast, the ignition must be so far advanced (i.e. timed to take place
early) as to allow the maximum pressure to occur when the piston
has only just passed over its dead point. When ignition timing
is correct, the maximum pressure may be taken as about 450 lb.,

and the average pressure during the working stroke as about 100 lb.

per square inch. Of course, if the ignition is too far advanced,
the exploding gases may administer a blow on the head of the
rising piston, and produce a knock. The phenomenon of knocking
is very curious, and is often the subject of heated argument. If,
on the other hand, the ignition is not advanced proportionally
to the engine speed, the full pressure will not be reached until
the piston has moved an appreciable distance on its downward
stroke, and some of the energy of the explosion will be lost.

If by some mischance a gross error of timing were made in

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the direction of retardation, or lateness, so that the piston had
moved far down the cylinder before the explosion occurred, the
mixture would burn slowly instead of exploding, there would be
little power, and the exhaust gases would be still flaming when
they were finally allowed to escape, so the exhaust valve would be
liable to be badly burnt. It is for a similar reason, namely, slow
and imperfect combustion, that a weak mixture, containing an
excess of air compared with the amount of petrol present, may
cause burning of the exhaust valve. This effect of a weak mix­ture sometimes appears to the novice rather paradoxical. In

point of fact, of course, the whole object of the internal combus­tion engine is firstly to develop heat, and then to convert it into

work. If through the use of an unsuitable mixture, or by faulty

timing of the ignition, the working conditions of the engine are
such that the heat cannot entirely be transformed into work,

we get the dual conditions of (1) loss of power, and (2) an excess
of heat in the exhaust gases with consequent damage to the

exhaust valve during the exhaust stroke.

4. Exhaust Stroke. The exhaust valve now opens, and the

products of combustion are ejected from the cylinder into the

exhaust pipe and silencer by the ascending piston. After under-

going cooling the burnt gases are now finally allowed to escape

into the atmosphere.

THE PRINCIPLE OF THE CARBURETTOR

The problem of perfect Carburation is a very complex one, and

as yet unsolved, for it is dependent on many factors. The chief
difficulty which presents itself is the constantly varying engine
speed and load. A certain mixture of petrol vapour and air is
only suitable for an engine running at a certain speed and with a

certain load, and should the speed or the load vary, the mixture

should also be varied to meet the new conditions. Up to now it

has not been possible to construct an instrument which will pro-

duce the necessary alterations exactly, and the best carburetting

system is, therefore, a compromise. Other complications intro-

duced are: the temperature of the engine and of the air, density
of the atmosphere, and quality of the fuel. Petrol spirit used for
ordinary motor work is a doubly distilled, deodorized spirit, of
about ·700 specific gravity, derived from crude petroleum. Other
fuels, however, including benzol and paraffin, may also be used,

but are not satisfactory except in the case of benzol, which is

commonly used. Discol is frequently used for racing purposes.

It is essential that a high-speed engine should run on a fuel having
a high degree of volatility.

The carburettor is an atomizer, and its duty is to convert liquid

petrol into a mixture of air saturated with the finest particles of

6—(5301A)

73

FIG. 31.

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SINGLE-CYLINDER

Measured in degrees of crankshaft rotation with a valve clearance of ·006 in.,
giving a valve lift of ·3125 in. This diagram is interesting from a theoretical
aspect only, for in practice the motor-cyclist never has occasion to retime his

* The correct ignition advance in the case of all A.J.S. engines will be

found in the specifications in Chapter I.

VALVE TIMING DIAGRAM

valves since the timing pinions are carefully marked (see page 128)

S.V. AND

OF

O.H.V. 3·49

1929-33 (SERIES

H.P. AND

M, R, S, T)

4·98

H.P.

ENGINES

HOW THE ENGINE WORKS 75

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fuel in the right proportions under all conditions; the correctness
(approximate) is attained by either automatic, semi-automatic,
or controlled means. In the case of the Amal carburettor {see
page 79), used on all A.J.S. machines, the action is semi-auto­matic. The general principle on which all carburettors work will
now be reviewed.

It has been found by experiment that the most satisfactory
way of encouraging petrol to evaporate is to drive it under pressure
through a very tiny hole, called a jet, and the process is assisted
by heating the spraying device. Owing to the proximity of the
carburettor to the combustion chamber, ample heat is, of course,
conducted to it via the induction pipe, once the engine has warmed
up. In practice it is not common to employ forced induction,
or supercharging (i.e. to blow the mixture into the cylinder).
Moreover, it is entirely unnecessary for normal requirements in
the case of motor-cycle engines. The powerful suction through
the inlet pipe on the inlet stroke can be relied upon to atomize the
fuel completely. Let us refer to Fig. 32, which shows the salient
features of a carburettor in action. It will be observed that the
petrol level in the jet must be below the orifice at the top ; other­wise the petrol will overflow and cause flooding of the carburettor.
The level is automatically regulated by the action of a float
attached to a spindle, which operates a needle valve, thereby

cutting off the petrol supply immediately the level in the chamber

reaches the height of the jet orifice. On the downward stroke of

the piston, air is sucked in through the air intake, past the par­tially open throttle, which is a closely fitting hand controlled
slide, operating up and down in a barrel, past the jet, past the inlet
valve, and thence into the cylinder. The extremely high velocity
air current that must obviously sweep over the jet causes the fuel
to issue in a small fountain, and simultaneously causes the spirit

to be atomized and diffused with the air rushing in towards
the combustion chamber. This, briefly, is the principle of the

carburettor.

Actually, no carburettor is by any means as simple as that shown

in the diagram, for consider the failings of such a carburettor.

The rider will wish to vary the speed of his engine to meet various
conditions ; he could do so by opening or closing the butterfly
throttle valve or gas tap shown in the diagram. But, unfortu­nately, petrol and air are dissimilar vapours, and do not respond
evenly to varying suctions; so the carburettor illustrated will
give a mixture of different proportions for every throttle setting,
and since petrol and air are only highly explosive when mixed
roughly in the proportions of 13 : 1, only one of these settings will
be correct. This might work tolerably well in the case of a sta­tionary gas engine with a governor, but would be quite hopeless

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for all locomotion purposes. Thus it is essential to be able to
control the gas and air independently. This can be done by
having two slides working independently—one for throttling the
air intake and one for throttling the entry to the induction pipe
(see Fig. 30). Hence, although the air intake may be fully open,
a high velocity air current over the jet can still be obtained with
the gas throttle only slightly open. And so the amounts of gas

and air can be varied at will to suit the conditions.

The various refinements and complications that arc incorpor­ated in all modern proprietary carburettors (including the Amal)

THE BOOK OF THE A.J.S.

FIG. 32. ILLUSTRATING PRINCIPLE OP THE CARBURETTOR

are designed to (1) make the mixture as homogeneous as possible,

(2) simplify the control, (3) enable automatic slow running to be

obtained, (4) enable settings for special purposes to be made.

THE IGNITION SYSTEM

The High Tension Magneto. This (a Lucas on all A.J.S.

machines) is so called because, unlike an ordinary dynamo, it
generates a small current at a very high voltage. An experiment

that demonstrates this very convincingly(?) is to place a finger on
the plug terminal while the engine is “ticking-over.” The instru­ment is very complicated, and requires very delicate handling

when being taken to pieces; no amateur ever dreams of dissecting
a magneto. Magnetos of to-day are extraordinarily reliable

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instruments, and seldom give trouble. When trouble does arise,
it can usually be located in the contact breaker (see page 121),
and can be remedied easily by almost anyone. Therefore, we
will conclude this chapter with the briefest description of the

magneto, and Low it works.

The magneto primarily consists of three parts—(1) the armature.

(2) a “U” shaped magnet, (3) the contact breaker.

The armature comprises an iron core or bobbin of “H” sec­tion, on which are two windings : firstly, a short- winding of fairly
heavy gauge wire, and secondly, on top of the former, a very big
winding of fine wire. The first winding is known as the primary
and the second as the secondary.

The armature, which can rotate
on ball bearings, is placed so that
on rotation it periodically cuts
across the magnetic field of the
magnet, and creates a current in the
primary winding. Incidentally, the
contact breaker forms part of the
primary circuit. This current, how­ever, is at a very low voltage—far
and away too small to produce any­thing in the nature of a spark. But
if a break is suddenly caused in the
primary by separating the platinum
contacts when the current is at its maximum flow, a high voltage
or tension current will be instantly induced in the secondary
winding—sufficient to jump a small space, if the circuit be in­complete. In this circuit the sparking plug is included, and
things are so arranged that, in order for the secondary circuit to
be complete, the current must jump across the electrodes of the
plug, or, in other words, a spark must occur. Now in the case of
a single cylinder engine, the points in the rotating contact
breaker separate once in every armature revolution (there being
one cam only), and the armature to which the contact breaker
is fitted being driven off the inlet camshaft by sprockets and
chain consequently runs at half engine speed; that is to say, a
“break” takes place once every two engine revolutions, i.e. four
strokes of the piston. Hence if the initial “break” be timed to
occur when the piston is at the top of the compression stroke, all
the other “breaks” (and therefore sparks) will occur at this point
also, and thus the engine will go on firing correctly. Besides the

“break” being timed to take place when the piston is in a certain
position (which we call “timing the magneto,” see page 124), it
must also be timed to occur at the moment when the bobbin is
having the greatest effect on the magnetic field (see Fig. 33).

FIG. 33. POSITION OF MAGNETO

ARMATURE WHEN CONTACTS

SHOULD OPEN

77

78

THE BOOK OF THK A.J.S.

This, of course, is allowed for in the design of the magneto, and
does not really concern the reader. Also, it is essential that the
primary circuit should be complete (i.e. the contacts must be
properly closed) both before and after the “break,” which

should be of very short duration.

The cam ring, against which the cam of the contact breaker
works, can be rotated by handlebar control through about 30°,
thereby giving means of advancing and retarding the spark.

The condenser is a device for the purpose of eliminating “arcing,”

and the distributor, a “brush” mechanism for distributing

FIG. 34. MAGNETO IGNITION WIRING DIAGRAM

the H.T. current collected off the slip-ring (which is connected
to the secondary) to the H.T. plug leads. A distributor is, of

course, fitted only in the case of the Big Twins, and rotates at

half engine speed.

For convenience in enabling the reader to obtain a better idea
of the relation between the various parts and how they function
as a whole, a wiring diagram of a simple magneto ignition system

is given on this page. This diagram, if studied carefully in con­junction with the above general description of the H.T. magneto,
should give an excellent idea of how that instrument, so often
regarded as a complete mystery, operates. We will not enter
into details of the method of construction since, as previously
pointed out, beyond attention to the contact breaker (see page 124)
the motor-cyclist is never likely to have cause to tamper with
the magneto and is certainly ill-advised to do so. So much, then,
with regard to the generating portion of the ignition system.

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The Sparking Plug. Passing reference has been made in respect

of the “results” end of the system, i.e. the sparking plug. This

small member requires and deserves some further consideration.

It is astonishing how efficient modern sparking plugs are, consider­ing the enormous heat they are subjected to, and the millions of
hot sparks they are called upon to deliver during their working
lives. The “expectation of life” of
the present plug is nearly double
that of plugs made a few years
back.

The purpose of the sparking plug
is to provide at regular intervals a
spark in. the combustion chamber.
The electric current for this job
is generated, as we have seen, by
the magneto. Fig. 35 shows the
construction of a Lodge plug.
That shown is partly sectioned.
It comprises a piece of insulating
material E held in a metal support
consisting of the plug A and the

gland nut B which are locked to-

gether firmly and screw into the
cylinder head. Down through the
centre of this insulator (usually

mica, porcelain, or steatite) passes
a thin metal rod D which is known

as the centre electrode. To its upper
end is attached a terminal F which
holds fast the H.T. “juice” wire

from the “mag.” At its bottom

end are placed either one or two
earthed electrodes (the plug shown
has two) in close contact with, but not touching, the central

electrode. Sparks jump from the centre to the earthed electrodes

as soon as a current of sufficient voltage to jump the gap at the
electrodes is generated by the magneto. Clearly the gap at the
electrodes is of great importance (see page 122).

According to whether there are one or two earthed electrodes so

is the sparking plug known as a “single point” or a “two point.”

FIG. 35. THE LODGE SPARKING

PLUG

79

SOME A.J.S. MECHANICAL DETAILS

The Amal Carburettor (fitted to all present models). This

instrument combines the best and most useful characteristics of
both Amac and Brown and Barlow instruments. It is thus a
thoroughly “brainy” job, and gives remarkable results. On the

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opposite page is shown a sectional view of the Amal two-lever
carburettor, and its working will now be described. It is presumed

that the reader is cognizant of the principle of the carburettor
already clearly set forth. Space and time will therefore not be
wasted in proffering redundant information on the action of the

float, etc.

In connection with the float chamber of the Amal it should be

pointed out that alteration in the float position can only have
detrimental results.

Referring to the sectional diagram which illustrates the con­struction, A is the carburettor body or mixing chamber, the
upper part of which has a throttle valve B, with taper needle C
attached by the 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 air passage 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 jet block is the adaptor body H, forming 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. 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 suitably mounted on a platform S containing the
float T 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 feed hole K; the level in these jets being, obviously, the
same as that maintained in the float chamber.

Imagine the throttle valve B very slightly open As the piston
descends, a partial 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. The quantity of mixture

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81

FIG. 36. SECTIONAL VIEW OF AMAL SEMI-AUTOMATIC TWO-LEVER

This carburettor was fitted to the whole of the 1930 and all except S8, SB8,
SB6 of the 1931 A.J.S. range and replaced the Binks model. These three
machines had the new Bowden carburettor. The manufacturers of Amac,
B and B, Binks carburettors have now amalgamated, and the Amal carburettor
is their latest achievement. For 1932 the Amal instrument is fitted to all
models, although some early 1932 T8, TB8, T6 models had the Bowden
carburettor. Except in the case of Model T5, the clip fixing shown is
replaced by a flanged fixing. All 1933 machines will have the Amal instrument.

The throttle stop is not shown in the above view

CARBURETTOR

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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 a further supply of 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.

As the throttle valve is opened farther the fuel passes the main

jet P, and this jet governs the mixture strength from seven-

eighths to full throttle. For intermediate throttle positions the
taper needle C working in the needle jet O is the governing factor.
The farther the throttle valve is lifted, the greater the quantity
of air admitted to the engine, and a suitable graduation of fuel
supply is maintained by means of the taper needle. The air
valve D, which is cable-operated on the two-lever carburettor,

has the effect of obstructing the main throughway, and, in conse­quence, increasing the depression on the main jet, enriching the
mixture. An accelerating pump unit may be fitted if desired.

The Bowden Carburettor (fitted to some 1931-32 models). This

carburettor, introduced for the first time last year on three of the
A.J.S. range, is an entirely different design from the Amal car­burettor just described. Besides having a butterfly valve instead
of a throttle slide, it has a completely automatic action. Although
two controls are provided, the twist-grip throttle control is the
only one required to be used while driving. The second control

(the mixture control) is opened only for starting purposes. Thus
manipulation of an air lever while negotiating traffic is not neces­sary, with consequent low petrol consumption, absence of sooting
up of plugs and general efficiency, the mixture being correct
under all conditions.

If desired, an accelerating pump unit can easily be fitted to the
Bowden carburettor. It is an excellent extra obtainable from the
manufacturers, and provides ultra-rapid acceleration without
supplying excessive fuel to the engine. Hints on tuning the
Bowden carburettor will be found on page 131. The principle of the
carburettor is as follows.

Automatic action of the carburettor is obtained by means of a
submerged jet, combined with two air injections in series, taking
place at different engine speeds. Most people realize that a cali­brated jet subjected to a variable suction, will not, under varying
conditions of depression, deliver a proportionate weight of petrol
to the weight of air passing through the choke tube. If, for
example, such an arrangement is used to provide a correct mixture
at medium engine revolutions, the mixture supplied at higher
engine revolutions will be much too rich. This is corrected by an

THE BOOK OF THE A.J.S.

FIGS. 37, 38. SECTIONAL VIEWS, SHOWING DESIGN AND ACTION OF THE BOWDEN AUTOMATIC CARBURETTOR

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air injection which reduces the flow of petrol through the jet, and
prevents it from increasing too quickly in relation to engine speed.

However, above a certain speed, the mixture has a tendency to

become rather rich again, and the single air injection is no longer

effective.

In the Bowden carburettor, a second air injection is provided

which works in series with the. first one. The various means of
adjustments for tuning on the Bowden carburettor, ensure that if
can be made automatic for any particular engine. Special devices
and adjustments are provided to ensure easy starting, slow
running, and rapid acceleration.

Figs. 37, 38 show sectional views of the Bowden carburettor

from winch its general design may bo understood. With flu

engine stopped, the petrol coming from the float chamber passes
through the total jet F. By the holes D it reaches the pilot jot

G, and through the hole E, fills up the pilot jot well. In the illus-

tration it will be seen that the petrol goes info the full jet A.
passing through the main jet B, which is the power jet of the
carburettor. The pilot jet G is therefore slightly above the petrol
level; the main jet B is under this level, together with the total

jet F. These two jets are called submerged jets.

In addition, and independently to the two principal air intakes
through the choke tube and venturi (air guide), three other small
air intakes are provided at different points in the carburettor;
at P, where the intake is regulated by a needle valve, controlled
by a lever on the handle bar; at N, an air intake for slow running,
adjustable by means of a screw M. A third intake is provided
underneath the slow running intake, and by a suitable channel
air is brought to the pilot jet well K.

Referring to Figs. 37 and 38, let us see exactly how' the Bowden
carburettor functions. When starting the engine, the butterfly
being almost closed, the suction on the full jet A is negligible.

The channel delivering the mixture for slow running comes out
at the edge of the butterfly, causing very great suction on the

pilot jet G. This suction can be increased by closing, partly or

fully, the air intake at P, by means of the mixture control lever,
in the case of the starting of an engine from cold.

For slow running, the pilot jet G delivers the petrol, which is

atomized by the air coming from the intakes N and P. The

mixture thus formed passes to the butterfly, where it is mixed

with an additional quantity of air, regulated by the opening of
the butterfly, and is then delivered to the cylinder.

As the butterfly is gradually opened, the suction on the full
jet A becomes stronger. This jet delivers petrol, and as air enters

into the pilot jet well K, through the suitable channel, the petrol

level in this well falls down until the duct communicating with the

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annular passage C is fully uncoverd. At this moment the sub­merged main jet B delivers petrol into full jet A, and to prevent

an increase of this delivery with the increase of the engine speed,

if is corrected by a first air injection passing through the suitable
channel into K and C. When the throttle is fully opened, the
remaining petrol contained in the pilot jet well K and inside the
pilot jet G is drawn through holes E and D, allowing the air to
pass through the same holes, when it becomes mixed with the

85

FIG. 39. SHOWING GENERAL ARRANGEMENT OF 1929-1930 DRY SUMP

On 1931-33 “T” models the general principles of the system and details
are different (see Figs. 10, 22, 40), the pilgrim pump being situated differently,
and the oil being fed to the timing side of the crankshaft instead of the driving

side and not kept in constant circulation between the engine and tank

petrol delivered by total jet F. The result is a fine emulsion of
petrol and air, made possible by this new air injection.

At high engine speeds the submerged total jet F is subjected to

a first air injection through D. The petrol and air emulsion passes

through the main jet B, when a second air injection takes place
in the annular passage C. The petrol mixture delivered by full
jet A has therefore been subjected to two air injections in series.

It is then finely emulsionized. This emulsion is finally diffused in

the main air current coming through the venturi and choke tube

before it passes into the cylinder. Acceleration at small throttle
openings is ensured by the reserve of petrol contained in well A C .

This petrol is rapidly drawn into the cylinder when the throttle
is opened quickly.

1926-28 Mechanical Lubrication System. Prior to 1929 it was

the practice for the A.J.S. concern to fit to all production models

LUBRICATION SYSTEM

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an engine lubrication system, comprising a Pilgrim mechanical

pump (see page 37), gravity-fed from the oil compartment of the

tank, and an auxiliary spring-loaded hand pump, or in some cases
a hand pump only. This system has worked fairly well, but its
day is now definitely past. During the past three years a new and

THE BOOK OF THE A.J.S.

OIL FEED TO BIG END ON

1931—33

MECHANICAL LUBRICATION

Only one of the driving side

mainshaft ball bearings is shown

infinitely better system of mechanical lubrication has been evolved
and perfected by the experimental and research department. The
first machines fitted with this system were overhead valve racing
machines, and these, later on, were followed by the O.H.V.
standard models. Various races were entered, including the
T.T. races, and the functioning of the lubrication carefully noted,
and various minor defects afterwards remedied, with the result

that to-day it is almost perfect after a few initial disappointments,

and is standardized on all models except the 1933 camshafts and

FIG. 40.

A.J.S.

ENGINES

WITH

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big twins. The main oil supply is now capable of adjustment
by a control knob.

The 1929 30 Dry Sump System. This is shown diagrammatic-

ally in fig. 39, while Fig. 41 shows how the oil circulates. The
essential difference between the dry sump system and other
methods is that in the former case a large quantify of oil is in
continuous circulation throughout the engine and tank, while in

the latter case only a comparatively small volume of oil at any
given time is circulating. Chief among the advantages accruing
to the D.S. system are the following: (a) No attention is required

by the rider other than maintaining the oil in the separate tank
mounted on the rear down tube at the correct level. (b) Superior
cooling of the engine lubricant is obtained. (c) Simple means for

filtering the oil and preventing the rapid accumulation of pul­verized carbon deposits can be provided. (d) There is no possi­bility of the engine being greatly over-oiled since the sump remains
practically “dry,” all superfluous oil being returned to the tank
by the duplex pump. (e) Oil consumption remains remarkably
low, due to a minimum of leakage or combustion taking place.
So much, then, regarding the merits of the system. We will now
inquire into the construction and working of the 1930 system.

The "heart" of the circulation system is the duplex pump D

driven by a simple coupling from the inlet cam shaft. Lubri­cating oil from the main tank A is drawn via the pipe C, after
passing through the filter B, into the pump itself and thence

projected along pipe E to the near side of the engine. It then
passes down through a channel in the crankcase and is forced,
under pressure, into the hollow mainshaft (see Fig. 41) along
which it travels to the all-important big end roller bearing. This
it very thoroughly lubricates as the oil oozes out and drips upon
the flywheels which, by centrifugal force, splash it upon the
cylinder walls. Oil mist, in fact, penetrates throughout the
working parts. Oil is also pressure-fed to the timing case. It
should be noted from Fig. 41 that by rotating the needle valve,
seen on the left, a few turns, lubricant can be fed direct to the
cylinder walls via a by-pass. This, however, is only intended for
fast racing work. All lubricating oil, after effecting its purpose,
eventually drains to the bottom of the sump, thence to be returned
to the pump via the pipe 67 (Fig. 39) after passing the second
filter F. Finally, it is forced under pressure up the pipe H and

back into the tank again to be recirculated ad infinitum.

1931-33 Improved Mechanical Lubrication. All 1931 to 1933

engines, except the 33/2 models and "camshafts," incorporate a
lubrication system quite different from the 1930 system in principle
as well as design. The oil in the tank is not kept in constant
circulation, and the duplex Pilgrim pump (Fig. 22) is driven from

87

the crankshaft. The upper plunger sucks oil from the tank via

the delivery pipe, and delivers if direct to a false bearing on the
timing side, not the driving side, of the crankshaft. The oil-way
is totally enclosed, no pipe being used as on the 1930 system.
The oil is then pressure-fed to the big end bearing, as shown in

Fig. 40. Some of if is also forced to the timing gear. Surplus oil

drops down from the big end on to the flywheels and is distributed

FIG. 41 OIL CIRCULATION ON 1929-30 DRY SUMP MODELS

by splash throughout the engine. The lower pump plunger collects
some oil from a by-pass from the main feed and returns it to the
tank via the return pipe, from whose orifice oil may be seen
emerging on removing the filler cap. There is no separate oil feed
to the cylinder walls as on the D.S. system, but the main supply

can now be controlled by means of the regulator on top of the
pump, illustrated on page 37. The oil return to the tank only
shows that the pump is working.

The Dry Sump Lubrication System (Big Twins). The lubrication

system for 1933 does not apply to 1931 or the “camshaft” models.

It is of the force-feed, constant circulation type with dry sump.
Briefly its working is as follows: Oil is sucked from the tank,
distributed throughout the engine, and finally returned to the
tank by a duplex internal pump. This comprises a single double­acting, steel plunger (Fig. 41A), housed in the crankcase casting

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below the timing case between two rectangular end caps hori­zontally and at right angles to the crankshaft axis, and able
simultaneously to rotate and reciprocate. This dual action of
the plunger is obtained, as is more fully explained on page 90,
by the fact that while a, positive rotation at one-fifteenth engine
speed is effected by direct engagement of a central hobbed
portion with a. worm cut on the mainshaft, an endwise movement
is secured by having an annular cam groove cut in the plunger

body in permanent contact with the hardened end of a fixed guide
screw. The actual oil circulation is brought about by alternate
displacements and suctions af the two ends of the reciprocating
plunger, one end being of greater diameter than the other to
ensure complete scavenging of the sump and the return of all
surplus oil to the tank. Two segments cut in the plunger body
constitute the main ports which regulate the circulation. There
is no adjustment however. A point worthy of notice here is

that the crankcase cannot safely be split until the pump plunger

has first been removed.

With regard to the actual oil distribution, the system adopted
is made clear by reference to Fig. 41A. The small end of the
plunger (i.e. the front one) forces oil up into the timing case to a
predetermined level, such that the camshaft bearings and drive
are adequately lubricated. All surplus oil overflows into the

flywheel chamber, and is eventually returned to the sump, al-

though some of it is caught up by the flywheels and splashed upon

the big-ends and the cylinders. Splash lubrication, however, is
not relied upon to any extent owing to the small volume of oil

remaining at any time in the sump. Oil is forced under pressure
direct to the big-end bearings and to the crankshaft bearing on

the timing side by means of carefully drilled passages in the fly­wheel and mainshaft concerned, respectively. Oil is also fed to
three points on each of the cylinder walls in such a position that
the bulk of the oil is discharged on to that part of the thrust side
of the cylinder walls where the maximum cooling effect upon the
pistons is required.

The constant circulation system with fabric filter (see page 22)
guarantees a continual supply of clean, cool oil to the engine
whenever the latter is running. The oil circulation may be

verified occasionally by removing the oil tank filler cap and
noting whether oil is being ejected from the return pipe orifice.
This check upon the oil circulation should be made preferably
upon starting up the engine from cold. Remember the fact that

when the engine has been left stationary for some time, oil from
various parts of the engine has drained to the sump, and, until
this surplus has been cleared, the return to the tank is very

positive, whereas normally it is somewhat spasmodic and,

7—(5301A)

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perhaps, mixed with air bubbles, due partly to the fact that the
capacity of the return part of the pump is greater than that of the
delivery portion, and partly to the (act that there are considerable
variations in the amount of oil held in suspense in the crankcase.

For example, upon suddenly accelerating, the return flow may
decrease entirely for a time only, of course, to resume at a greater
rate than before when decelerating. If may be mentioned,
however, that on all Big Twin models the provision of a. tell-tale

on the instrument panel, illuminated at night, obviates the

necessity for removing the filler cap, the oil supply to the timing­box being first by-passed up to the panel. It is important that
no air leaks occur in this system.

The Double-acting Oil Pump. A general description of the

33/2 dry sump lubrication system has already been given, and
Fig. 41A shows how the oil is circulated. It remains to deal with
the action of the pump itself. As already mentioned on page 89,
the pump has only one moving part—a steel plunger driven at

1

/15 engine speed by a worm cut on the engine mainshaft. This
plunger slowly oscillates to and fro, its precise travel being deter­mined by the relieved end of a guide screw (b. Fig. 41A) screwed
into the rear of the pump housing and engaging with a profiled
cam groove at the large return end of the plunger. This groove
plays an all important part. In addition to causing the plunger

to oscillate and thereby obtain a pumping action at each end (for

the plunger is completely enclosed by its housing and end caps),
its carefully planned contour enables the pumping impulses to be

synchronized with the opening and closing of two main ports
and a small auxiliary port, thus definitely regulating the oil cir-

culation and controlling the supply of oil to the engine and the

return of oil to the tank.

The two main ports are shown at D and C, and the small
auxiliary port at E, Fig. 41A. The main ports are known as the
delivery port and the return port respectively. They comprise two
shallow segments cut in the pump plunger body and communicat­ing with the hollowed ends of the plunger by two holes. The
auxiliary port comprises simply an 1/8 in. diameter hole drilled at
the back of the main delivery port segment. The plunger itself,
as mentioned on page 89, has two diameters, and, therefore, the
capacity of the return portion of the pump is greater than that
of the delivery portion, so that the sump is always kept clear of
oil. Fig. 41A enables the action of the pump to be understood.

Oil flows by gravity, assisted by suction, from the tank to a point
in the pump housing, such that no further passage can take place
until the plunger has moved to a point, approximately, as shown
when oil flows into the hollowed end via the cut-away segment
constituting the delivery port. Then as the plunger continues to

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HOW THE ENGINE WORKS

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advance with simultaneous reciprocation, the oil which has com-

pletely filled the hollowed end is momentarily retained and the

bulk of it finally ejected by displacement from this port into an
oil passage opposite the point of entry, and forced to the cylinder
walls and main engine bearings. During the advance of the

91

FIG. 41A. DIAGRAM SHOWING THE OIL CIRCULATION IN THE DRY

SUMP LUBRICATION SYSTEM USED ON THE 1933 BIG TWINS

The 1933 “camshaft” models have a different type of lubrication system

Inset is shown the pump plunger itself, whose parts are as follows—

A—Hobbed portion of plunger C—Plunger return port
B—Annular cam groove D—Plunger delivery port

b—Guide screw (crank case) F— Small auxiliary port

plunger culminating in the automatic injection of fresh oil into

the engine, the receding of the large end of the plunger causes a
strong vacuum directly opposite an oil passage leading from the
sump base, and communicating with the plunger interior only
when the return port is in a suitable position. All surplus oil in
the sump is, therefore, sucked up as the plunger advances, and

retained when the port closes until the plunger begins to reverse

its motion, when the return port, corning into line with the return

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pipe passage, the oil is forcibly ejected by displacement into this
pipe, and so to the oil tank, where its intermittent emergence can,
though a tell-tale (Fig. 19a) is provided, be observed.

Thus it will be seen, that so long as the engine is running fresh
oil is being constantly fed to it and then, after circulation, sucked
from the sump and forced up back into the tank to be recircu­lated ad infinitum. Coincident with the ejection of oil from the
main delivery port a supply of oil is forced out of the auxiliary

port to the timing box. Since a tell-tale is provided it is first

forced up into the panel, whence if flows by gravity to the respec­tive parts requiring lubrication. Only a small portion of the total
oil feed to the engine is diverted in this manner, but this portion
is important and a definite index as to the correct functioning of
the whole D.S. lubrication system, for only when the pump is

forcing oil into the engine at a certain pressure can the rise of the

tell-tale plunger be observed. The action of the pump plunger is
almost, fool-proof, but care must be taken to remove the plunger
before separating the crankcase, and the guide screw (b) must
always be kept fully tightened. A point worthy of note is that
with the plunger stationary no oil can possibly enter the engine.

The Sturmey-Archer Gear-boxes. There are three types of

gear-boxes fitted to A.J.S. machines—the new heavyweight four­speed, the heavyweight three-speed (TBS, T9), and the lightweight
three-speed boxes (T5, TB6). On the two first mentioned the
layshaft is below the mainshaft, but in the latter case the layshaft
is placed immediately behind the mainshaft with a totally­enclosed kickstarter drive taken through the low gear pinions.
The heavyweight four-speed gear-boxes are standard S.A. gear­boxes, except that they have a special end cover, having a
swivelling fulcrum arm and anchorage. The clutch-operating­control on all boxes comprises a lever mechanism. Both three­speed boxes work the same, though some constructional features
are different (page 97).

The Heavyweight Four-speed Gear-box (Standard on Models

T6, T9, 33/2). Referring to Fig. 42, the clutch body (14a) is

keyed and held by a nut to the end of the mainshaft (1). Rigidly

fixed to the clutch body and moving with it are four driven

plates (14) kept in contact by the clutch springs (15) with three
friction insert plates (13), of which the rearmost constitutes the
clutch sprocket (3) driven by chain from the engine sprocket.
These friction plates, owing to their construction (see page 137),
rotate when the engine is running as a single unit, and the driven
plates also rotate with them, except when the clutch spring pres­sure is released by the lever (17) through the plunger (16). It
will thus be seen that with the clutch engaged, the engine always
drives the gear-box mainshaft at a speed equal to the ratio of the

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93

engine sprocket diameter to the clutch sprocket diameter (i.e. at

about half engine speed).

The mainshaft itself is carried in two bearings, that on the

clutch side, where the secondary transmission thrust is received,

being a heavy single-row, self-alining ball bearing, and that on
the opposite side a light double-row ball bearing. The main­shaft, however, is not carried direct on the large bearing, for the

FIG. 42. SECTIONAL ARRANGEMENT OF STURMEY-ARCHER

HEAVYWEIGHT 4-SPEED GEAR-BOX AND 3-PLATE CLUTCH

Main shaft

1—
2—

Layshaft

3—

Clutch sprocket

4—

Gear-box sprocket

5—

Top gear dog wheel

5A—

Top gear dog wheel sleeve

6—

Mainshaft sliding dog wheel

7—

Second gear dog wheel

8—

First gear pinion

9—

Layshaft driving pinion

10—

Layshaft third gear dog wheel

11—

Layshaft sliding dog wheel

12—

Layshaft driven k.s. dog wheel

13—

Clutch friction plates

14—

Clutch-driven plates

14A—

Clutch body

3

5—

Clutch springs

16—

Clutch plunger

17—

Clutch actuating lever

18—

Kick-starter axle

gear-box sprocket (4), which is connected to the rear wheel sprocket
by chain, is rigidly attached to a sleeve (5A), which also carries

the top gear dog wheel (5), and the whole is free to revolve on

the mainshaft with a phosphor-bronze bush as a bearing. It is

the sleeve itself which is carried by the thrust ball bearing, and,

consequently, the loading of both primary and secondary trans-

mission is taken through this bearing. The top gear dog wheel

is in permanent engagement with a small fixed layshaft driving

pinion (9), and so the gear-box sprocket rotates whenever the

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layshaft is in motion, and vice versa. Adjacent to this small lay­shaft pinion is another slightly larger pinion (10), free to rotate
on the layshaft and dogged on its inner side. This pinion provides
third gear. Af the end of the mainshaft opposite the clutch are
two small pinions, the second gear dog wheel (7), free to revolve

on the mainshaft, and the low gear pinion (8), which is not dogged,

but is fixed to the mainshaft and in constant mesh with the large

FIG. 42A. THE STURMEY-ARCHER 4-SPEED TRAIN OF PINIONS

This illustration should be studied in conjunction with Fig. 42

THE BOOK OF THE A.J.S.

(Sturmey-Archer Gears, Ltd.)

layshaft driven kickstarter dog wheel (12), which can revolve
freely on the layshaft. As may be seen from Fig. 42, with the
gears in neutral, the kickstarter axle, when rotated anti-clockwise,
drives by means of the pawl and ratchet the large layshaft
k.s. pinion (12), which, in turn, rotates the first gear pinion and
thus drives the mainshaft and clutch sprocket clockwise. Taking
the engine sprocket into consideration, a total gear reduction of
about 4 : 1 occurs. Between the top gear and the second gear
mainshaft dog wheels on a splined portion of the mainshaft is one
of the two sliding pinions (6). Below this on a splined portion of
the layshaft is the second sliding pinion (11). Both these sliding
pinions are dogged on each side, and together are capable of

engaging four dog wheels.

A very clever cam operating mechanism, whose design is made

clear by Fig. 42B, co-ordinates and controls the horizontal mo-

tion of the two sliding pinions, which have grooves into which
the striker forks A fit. The cylindrical bases of the striker forks