Ajs 1948 1957 AJS Singles 5th Edition F Neill Ajs 1948 1957 AJS Singles 5th Edition F Neill

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C. ARTHUR PEARSON LTD

1948

2nd edition 1949

3rd edition 1952 4th edition 1952

Reprinted 1955

5th edition 1958

Printed in Great Britain by Richard Clay and Company Ltd.,

Bungay,Suffolk.

Page 5

PREFACE TO THE FIFTH EDITION

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HE fifth edition has been extensively revised to fully cover all single-cylinder A.J.S. models produced from

1945. The 350-c.c. is known as Model 16M or, in the case of a

spring-frame machine, 16MS. Similarly, the 500-c.c is described as Model 18M or 18MS. The first two figures in the engine number (stamped on the drive-side crankcase) indicates the year of manufacture; thus, engine number 48/16MS/0000 indicates a 1948 spring-frame 350-c.c. model.

The makers of these machines have incorporated many

basic design details from th e Army typ e model, wh ich h as a

world-wide reputation for efficiency and reliability.

The numerous modifications made a re des cribed i n seasonal order, to serve as a guid e to enable owners of early models to incorporate them in their machines, where it is possible.

Man y engine features on the post -war models ar e identical to th e pre-war mo del s; th us t he technical details given for the later models apply also to machines produced from 1938 up to

1939. How to improve the engine efficiency is described in

Chapter VIII, the treatment of the subject being on a practical basis, without theoretical reference. A chapter is devoted to Trials and Scrambles models, which are not

covered by the maker's handbook.

T he au thor wishes t o thank Associated Motor Cycles Ltd.

and Joseph Lucas Ltd. for co-operation and permission to reproduce their illustrations.

Th e publishers particularly wish t o thank Associated Mot or

Cycles L td . for permi ssion t o use th e A .J . S. T ra d e Mar k as a cover design.

F. W. NE ILL

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CONTENTS

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CHAP.

I. FAULT LOCATION AND ENGINE SERVICING 11

Locating the Source of Noise—Excessive Oil Consumption—Engine Smokes Excessively on Starting —Damaged or Worn Teeth on Pump plunger—Oil Supply Fails to Rocker Box—Cylinder Wall Feed— Crankcase Release Valve—Curing Oil Leaks—Oil Leaks from Cap on Timing-gear Cover—Wear on Valve Spring and Collar—Wear on Valve Ends and Rockers—Exhaust Valve Sluggish or Seizes in the Guide—Valve Guides Loose in Cylinder-head— Wear on Camshaft—Removing Valve Guides (All O.H.V. Engines)—Refitting Valve Guides—Bent Push Rods—ENGINE NOISES—Big-end Rattle— Piston Slap—Camshaft End-float—Timing-gear Noise—Noise in Rocker Box—Flywheel End-float

—ENGINE SERVICING—Decarbonising the Engine—

Valve Grinding—Removing Loose Carbon—Replacing the Cylinder-head—Refitting Rocker B o x Cleaning the Carburetter—Push-rod Adjustment— Refitting Petrol Tank—Checking Ignition Timing —Setting Ignition Timing—Lubrication System—

Oil Filters—Cleaning the Filter—PERIODICAL MAIN -

TENANCE.

PAGE

II. ENG INE OVERHAUL 36

DISMANTLING THE ENGINE—Engine Design Changes —Removing the Engine—Removing the Piston— Separating the Crankcase—Checking Big-end Assembly—Separating Flywheels—Removing Main Bearings—Removing Cam-wheel Bushes—Removing Tuning-side Bush—Connecting-rod Service —Removing Flywheel Shafts—Dismantling the Rocker Box—Engine Nut Sizes—Tappet-guide Removal—Replacing Flywheel Shafts—REASSEMBLING THE ENGINE—Flywheel Assembly—Crankcase Assembly—Refitting Driving-side Bearings—Refitting Camshaft Bushes—Refitting Tappets and Guides— Reassembling the Crankcase—Fitting Special Camshafts—Types of Special Camshafts—Increasing Compression Ratio—CARBUBETTERS (1945 O NWARDS)—Erratic Running at Slow Speeds—Heavy Petrol Consumption—Throttle Slide—Checking Petrol Consumption—Locating the Taper Needle— Banging Noise in

Silencer—THE

. . . . .

MONOBLOC

vii

CAR-

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CHA P .

CONTENTS

PAGE

BURETTER—Removing the Float—Removing the Float Needle—Removing the Pilot Jet—Jet-block Removal — Carburetter Adjustment — Excessive Petrol Consumption—VALVE TIMING—Refitting Cams—Checking Valve Timing—FITTING A LATER

TYPE ENGINE.

III. TRANSMISSION 68

Chain Adjustment—Tightening Front Chain— Rear-chain Adjustment (1950-54 Models)—Rearchain Adjustment (Detachable-wheel Models, 1955-57)—Dynamo-chain Adjustment—Tightening Dynamo Chain—Magneto-chain Adjustment— Rear-chain Adjustment (Rigid-frame Models)— Rear-chain Lubrication—GEARBOXES—GEARBOX

FAULTS

Top Gear Disengages Under Load—Faulty Gear Selection—Noisy Gear Engagement—Kick-starter Fails to Turn Engine or Jams—Kick-starter Fails to Operate—Side Movement, or Rock, on Clutch Sprocket—End Play on Gearbox Mainshaft— Broken Teeth on Gears—Clutch Rattle with Engine

Idling—GEARBOX

Selection—Top Gear Disengages Under Load— Gears Disengage Under Load—Noisy Gear Selection—Clutch Rattle—Foot-change Lever Sticks— Kick-starter Crank Sticks after Use—Oil Leakage from Gearbox, Driving Side—Oil Leakage from Kick-starter Case Covers—DISMANTLING AND RE-

ASSEMBLING GEARBOX IN THE FRAME—Removing

Exhaust Pipe, Silencer and Chaincase—Removing Clutch Assembly—Extracting Bushes—Reassembling Gearbox—Servicing Foot-change

Assembly—DISMANTLING AND REASSEMBLING THE

B52 TYP E GEARBOX IN THE FRAME—Removing

Kick-starter-case Cover—Refitting Kick-startercase Cover—Removing the Gears—Removing Main Driving Gear and Bearing—Refitting the Gears— CLUTCHES—Clutch Operation (C.P. Type)—Removing the Clutch Cable—Replacing the Clutch Cable—Lubricating the Clutch Cable—Clutch Slip —Dismantling and Reassembling Clutch Complete —1957 change Operation—Clutch Adjustment—ClutchSlip —Dismantling Clutch Assembly—Removing Gearbox Outer Cover—Removing Gearbox Inner Cover —Removing Cam Plate—Removing Gearbox Internals—Removing Oil Seal and Ball-races—Removing and Replacing Clutch Shock Absorbers— Clutch Bearing—Kick-starter Assembly—Reassembling the Gearbox—Refitting the Cam Plate —Refitting the Outer Cover—Refitting the Clutch Assembly.

(C.P.

TYPE

. . . . . .

TYPE,

1945-51)—Gearbox Noise—

FAULTS

GEARBOX

(B52

TYPE)—Faulty

(A.M.C.

TYPE)—Foot-

Gear

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CHAP.

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IV. FRAME AND FORKS l01

Steering-head Adjustment—Steering Troubles— Handlebars Wobble at Slow Road Speeds (Solo)— Fitting a S teering-damper—Checking Wheel Alignment—Steering Uncertain on Bends—"TELEDRAULIC" SUSPENSION—Faults in the Front Forks —Grating Noise with Fork Movement—Rattle in the Front Forks—Dismantling the Forks—Changing or Servicing the Fork Springs—Removing the Fork Slider—Replacing the Oil Seal—Checking the Oil Content (1948-50)—Checking the Oil Content (1951-57)—Removing the Front-fork Assembly—Refitting the F ront-fork Assembly—Removing a Fork Inner Tube —Completely Dismantling Inner-tube Assembly—Reassembling the Fork Inner Tube—Rear-suspension Service— Checking Oil Content (1946-51)—Completely Dismantling the Unit—Rear Suspension (1951 onwards)—Checking the Oil Content (1951 onwards) —Dismantling and Reassembling Rear-suspension Units (1951—54)—Rear-suspension Units (1957)— Removing the Springs (1957)—Removing the Oil Tank (1956-57)—Dismantling Rear-suspension Units (1955-56)—Removing the Oil Tank and Battery Carrier (1950-54)—Removing the Oil Tank and Battery Carrier (1955)—Permissible Frame Modifications.

CONTENTS

. . . . .

PAGE

V. WHEELS AND BRAKES 122

Adjusting Front-wheel Bearings—Dismantling Front-wheel Bearings — Adjusting Rear-wheel Bearings (Rigid-frame Models)—Dismantling Rearwheel Bearings (Rigid-frame Models)—Adjusting the Rear-wheel Bearings (Spring Frame)—-Dismantling Rear-wheel Bearings (Spring Frame)— Removing Rear Wheel (1955-57)—Refitting Rear Wheel (1955-57)—Rear-brake Drum (1955-56)— Rear-wheel Removal (Trials and Scrambles Models) —Removing Rear Wheel (1950-54)—Adjusting the Rear-wheel Bearings (1955-57)—1955-56 Quick Detachable Wheel—BRAKES—Removing and Replacing Brake Liners in Wide Hubs—Fitting New Liner—Brake-shoe Adjustment—Ineffective Brakes

—Brake Squeal—SIDECAR CONVERSION.

VI. IGNITION AND ELECTRICAL EQUIPMENT 133

Removing Contact-breaker (N1-4 Magneto)— Cleaning Contact-breaker Points—Checking Contact Point Gap—Cleaning Contact-breaker Points (Type SR1), Rotating-magnet Model—Checking Contact-breaker Point Gap (Type SR-1)—Converting to Positive Earth System—Removing the Mag-

. . . . .

. .

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CHAP.

CONTENTS

PAGE

neto—The Dynamo—Removing the Dynamo (All Models before 1953)—Removing Dynamo (Models after 1552)—Refitting Dynamo—Checking the Dynamo Output, Cut-out and Regulator Unit (A.V.C.)—Cut-out Contacts Burnt or Dirty— Cleaning Regulator Contacts—Testing Regulator— Regulator Adjustment—Testing and Setting the Cutout—Removing the Headlamp Front and Interior— Replacing the Headlamp Front and Interior—Removing the Headlamp Rim and Light Unit (Prefocus Type)—Replacing the Headlamp Rim and Light Unit (Pre-focus Type)—Sparking-plugs— Ammeter (Testing in Position)—The Battery— Lamp Bulbs Blowing.

VII. TRIALS AND SCRAMBLES MODELS 150

TRIALS

MODELS—Flywheels—Gear Chain Case—Converting Standard Models for Trials Work—Gearbox—Steering Angles—Brakes-— Preparation for Competition Riding—Electrical System—SCRAMBLES MODELS—High-compression Pistons—Sparking-plugs—Measuring Compression Ratio—Measuring Exhaust-pipe Length—Sparking-plug Register—Checking Connecting-rod Alignment—Flywheels—Short-circuit Racing—Wheel Balance—Racing Machine Check—T.T. Type Carburetter—Carburetter Settings—THE 1956-58

SCRAMBLES

Valve Timing—Checking Valve Timing—Ignition Timing—Exhaust Pipes—Carburetter—Gear Ratios —Fuels—Decarbonising—Major Overhauls— Timing-side Axle Bush—Flywheel Axles—Tappet Guides—Technical Recommended Lubricants.

VIII.

TUNING

Engine Assembly—Valve and Guides—Carburetters —Valve-spring Pressure—Fitting Special Camshafts—Racine Cams (SH Type).

IX. WORKSHOP TOOLS AND APPLICATION 169

TECHNICAL DATA 174

INDEX 183

ENGINES—Push-rod

Data—PERIODIC

THE

ENGINE 166

. . . . .

. . . . . . .

. . .

Ratios—Front

Adjustment—

MAINTENANCE

. .

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CHAPTER I

FAULT LOCATION AND ENGINE SERVICING

HEN any particular engine fault develops, the cause

should be investigated systematically, and, before deciding to fit expensive repl acements, which may prove to be unnecessary, a careful study of the information which follows on the various engine noises that are likely to develop should first be made.

Do not rely entirely on the advice given by the so-called expert, who does not have to foot the bill for unnecessary replacements. For example, camshaft end-float is invariably associated with small-end wear; thus it will often be found that after replacing the small-end bush and

gudgeon-pin,

noise due to camshaft end-float will still prevail.

Engine noises and when and how they occur are detailed to assist owners to locate the source, and also to avoid unnecessary expense in fitting new parts without just reason.

Where instruments for measuring engine parts are av

ailable and when an engine overhaul is contemplated, parts should be measured and checked against the sizes given in the

technical

data at the end of the book before new parts are used.

Locating the Source of Noise

Owners of A.J.S. models are strongly advised against the practice of using parts that are not made by the A.M.C. Company. There is no economy in using replacements of this kind, which can cause a serious engine failure.

Some owners concentrate on engine maintenance and overlook important frame, fork and gearbox parts. When an unusual noise develops, its cause should be investigated as soon as possible, otherwise expensive damage can occur. For instance, the exhaust pipe or silencer may become detached with the machine in motion.

When it is difficult to locate the source of any particular

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noise, let th e machine coast downhill, with th e engine sh u t off, and in neutral. A variety of noises may be audible, due to the rear chain fouling the chain guard, brake shoes rubbing on

the brake plate, gearbox bearing noise, squeaks in the suspension. T hese are the most likely noises and are not always audible with the engine under load.

Excessive Oil Consumption

If oil consump tio n increases progressively after considerable mileage, check piston-ring gap. The normal gap is 0·0030·004 in. for each 1 in. bore size. Should cylinder wear exceed 0·008 in. rebore th e cylinder and use an oversize pist on .

ORIGINAL MODIFICATION

FIG . 1.—OIL-PUMP PLUNGER MODIFICATION FOR 1947-48

A.J.S. MOTOR CYCLES

MODELS.

Pistons of dimensions +0·020 in. and +0·040 in. only are supplied. A chromed-top compression ring is recommended to minimise cylinder wear.

When this fault occurs and when rings and bore are un-

worn, check the valve guides for wear.

On engines with number before 9310 (350-c.c.) and 8765 (500-c.c.) an i mproved type of tappet guide can be used, which has an increased number of oil drain slots. After driving fast for a long distance, oil can pile up in the push-rod cover tubes, swamping the cylinder-head and guides. The oil will then enter co m bustion cha mb er and increase oil consu m ption . On 1947-48 models thi s can also cause th e ex haust valve to stick

in th e guide, due to excessive carbon on valve stem and guide.

Oil supply to the top of the engine can be reduced by a modification to the oil-pump plunger (see Fig. 1), which is made by the makers.

Incorrect setting of the regulating screw controlling the oil

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supply to the inlet guide will increase oil consumption, normal

setting 1/2 turn open from fully closed pos ition.

If Engine Smokes Excessively on Starting

This fault is most likely to occur on engines that have covered considerable mileage or where the oil-plunger housing in the crankcase is either scored or worn, allowing oil to seep into the crankcase whilst the engine is stationary. To check,

record the oil level in the tank with a dip-stick at night and check again on following day. If level has fallen seepage has occurred,

To remedy, send timing half of crankcase to the makers for

a bush to be fitted in the plunger housing.

Bad scavengin g of the su mp will have the same effect, and

may be due either to an air leak between the rear pump end

cap and crankcase or an obstruction in the oil-way from the

sum p to the oil pump.

To check, remove the oil-pump plunger an d the drain plug from the sump. A stiff piece of wire inserted through the plug hole in the crankcase and through the oil-way in the crankcase may dislodge foreign matter, such as a piece of broken piston ring, etc.

As a preliminary test, take o ut the oil filter an d not e if the oil return increases on running the engine. A choked oil filter will restrict the oil ret urn.

Damaged or Worn Teeth on Pump Plunger

A slight amount of teeth marking is normal after consider-

able mileage. If the teeth are badly damaged on th e plunger

all round, this can only be due to overload caused by the guide pin not being properly located in the plunger groove and

bearing on the plain diameter of the plunger. If the wear is excessive in one par t of the plunger, restriction on either the feed or ret urn side of the oil system is responsible.

T he ca use mus t be investiga ted and rectified before r eplac -

ing the plunger. T his can be due to :

(a) Obstruction in rocker feed passage, gasket in-

correctly fitted.

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(b) Obstruction in rocker-box oil-ways.

(c) Choked big-end feed (which is the most likely cause) due to foreign matter, or crankpin incorrectly located in flywheel, re st r icting oil feed.

After overhaul, when new parts have been fitted, use an old small-end hush placed on the timing-side axle, then squirt oil through the hole drilled in this bush. The oil should emerge each side of the connecting-rod if t he feed passage is correct.

Oil Supply Fails to Rocker Box

Check th e oil pump g uide pin for wear on the extreme e nd. This may curtail the plunger travel.

When investigating oiling trouble after overhaul, verify that the correct type of oil-pump plunger and also timing-side axle has been fitted. For models after 1946 the plunger can be identified by the number " 2S " stamped on it.

Cylinder-wall Feed

A.J.S. MOTOR CYCLES

This requires no attention and does not affect oil consump-

tion, as commonly supposed. The arrangement is not incorporated in the 1956-type engines.

Crankcase Release Valve

This is a flap valve mounted on the drive side of the crankcase, behind the front chaincase. A slight oil discharge on starting, which ceases whe n the machine is in motion, is of no consequence. If the valve is dismantled, use a little grease on the serrated seat to hold the steel diaphragm in position during assembly.

Curing Oil Leaks

Th e engines are usually free from oil leaks. If the engine is taken down, a gasket set for renewals should be available on assembly. Should oil leakage occur from the push-rod cover tubes, test for rigidity. If it is possible to move the

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FAULT LOCATION AND ENGINE SERVICING

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tub e s sl ight ly, u se a th in steel washer, 3 /6 4 i n. thic k, on t h e re -

duced end of the p ush-r od tubes to create additional press ure on the sealing rubbers. Avoid using gaskets not of A.M.C. manufacture, as these are unsuitable.

Oil leaks from the cylinder base can be due either to base nu ts not being evenly tightened or a deformed cylinder-base gasket.

When fitting a new gasket, all broken pieces of the old gasket must be removed from the crankcase face, particularly round the base studs, also from t h e c y l in d e r-base face. Apply

jointing compound on the cylinder only and stick the gasket to it. Do not use jointing compound on the crankcase face.

Oil Leaks From Cap on Timing-gear Cover

A new metal cap, which is inexpensive, is required to rectify an oil leak from this po int. T he old cap can be r emoved by piercing a small hole in it so that it can be levered out with a sharp-pointed tang of a file.

Clean away all traces of oil in the cap recess, apply jointing compound on the outside diameter of th e new cap and tap it home squarely. Do not run the engine until the jointing compound has bad time to set.

Wear on Valve Spring and Collar

Engi nes mad e before 1954 can be modified to overcome this

trouble by the following procedure:

(1) Increase the diameter of the oil hole drilled in th e box for the exhaust rocker in the rocker box to 3/16 in. diameter.

(2) Fit a metering plug, obtainable from the makers, Pa r t No. 018890 (i ns ert small hole e nd fi r st ) . T hi s altera-

tion will cut down the oil supply to the exhaust valve, which is already generous, and at the same time force more oil to the inlet rocker and valve end, red ucing wear on springs and collar.

(3) F it two new rockers for valve ends w ith oil groove

machined in sid e of rocker (Par t Nos. 022136, 022137).

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If so desired, 1952-type valve springs with open-tray-type seat can be fitted on earlier models using this type of valve spring.

Wear on Valve Ends and Rockers

This trouble is most likely to be associated with models made before 1954. The modification regarding wear on

valve springs will also eliminate t his wear.

To avoid expense in fitting new valves when wear takes place on valve ends, the original valves can be made serviceable by reducin g the rocker end of the valve by 3/32 in . and using ha r de n ed val ve -en d c ap s u se d up t o 1948 t o r es t or e th e valve

to its normal length. If the rockers for the valves are worn as a result of oil shortage, new ones will be required to maintain correct rocker adjustment.

Exhaust Valve Sluggish or Seizes in the Guide

If the engine misfires, or cuts out, accompanied with a

mechanical clatter, after driving hard, the exhaust valve is the

cause.

Engines with iron cylinder-heads are more prone to this trouble, which is due to a formation of carbon on the valve stem and in the valve guides, caused either by excessive oil or over-lubrication to the exhaust valve and guide. On engines made before 1949 a hole is drilled in th e well cast in the rocker box, which registers with an oil passage in the cylinder-head supplying oil by gravity. This supply, which is already generous, should be restricted to prevent a reoccurrence.

A standard metering plug (Part No. 018890) obtainable from th e makers, can be fitted in to the hole drilled in th e well for the rocker box. Ins ert the plug with the small hole down-

wards. Alternatively, use an aluminium plug with a slight

fiat filed on it and insert this plug into the hole in the cylinderhead which registers with the oil-feed hole in the rocker box. T he exhaust valve must be taken out (see " Decarbonising the Engine ", page 26), and all traces of burnt oil or c a rbon removed from the valve stem, and most important of all, from inside the valve guide, A narrow strip of emery cloth, together with

A.J.S. MOTOR CYCLES

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FAULT LOCATION AND ENGINE SERVICING

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a tommy bar, introduced into the guides can be used effectively. Ens ure tha t no abrasive, or loose carbon, is lodged in the valve-guide oil hole .

If a complete engine overhaul is contemplated and if the engine number is before 9310 (350-c.c.) or 8765 (500-c.c.) change the tappe t guide for the new ty pe with six slots. Thi s

will prevent oil accumulating in the push-rod tubes and swamping the cylinder-head, causing over-lubrication and

heavy oil consumption.

Valve Guides Loose in Cylinder-head

This can occur only on engines fitted with alloy-type cylinder-heads, and is usually connected with the exhaustvalve guide only. Scuffing by movement of the guide will tend to enlarge the hole in the cylinder-head.

Alternatively, if this guide is driven out without preheating the cylinder-head the same effect will take place.

To remedy, an improved type of guide (Part No . 022208), which uses a circlip to p revent the guide from moving, should be fitted and can be interchanged.

In cases where the guide is a very loose fit a copper deposit should be made on the outside diameter of the guide to in-

crease its effective size and close up the interference fit.

It is rare for the inlet guide to be similarly affected, but if

so, the same treatment should be applied. Alloy cylinder-

heads must be heated when fitting or removing valve guides.

Wear on Camshaft

If the apex of cams are worn or bruised, the reason should

be investigated before replacements are fitted. Should damage or undue wear take place on the apex or peak of t he cams, this can only mean that undue pressure occurs on the cams when the valve is at full lift.

In the case of engines fitted with coil-type valve springs th e springs may be of a type not made by A. M. C, which become coil bound, or close up solid when the valve is at full lift.

To check valve motion, rotate the engine until the valve

is at full lift. Then apply a box key on the rocker-axle nut

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FIG. 2.—THE LIGHT ALLOY CYLINDER-HEAD.

A.J.S. MOTOR CYCLES

T he dimensions shown on th e valve guides i n dicate the amount of

guide standing proud whe n the guide is correctly inserted.

Oil feed to inlet valve.

1. and 4. Carburetter mounting

2. stu d holes.

Inlet port.

Inlet-valve spring seat dowel

5. hole.

Inlet-valve guide. Sparking-plug hole.

Oil feed to exhaust valve.

Exhaust-valve spring seal

9. dowel hole.

10.

Exhaust-valve guide.

11.

Exhaust-valve-guide circlip. Exhaust port.

12. Inlet-valve oil-feed adjust-

13.

ing screw.

14.

Locking-nut for 13.

and endeavour to open the valve a little farther. If no movement is apparent the valve springs are closing up solid, and this is responsible for cam wear.

To remedy, fit A.M.C. valve springs, or ascertain that the valve-guide protrusion is not in excess of the specified leng th (see Technical Data at the end of this book).

On old engines a badly worn or damaged tappet foot will damage the cams. With engines using hair-pin valve springs contact with the valve-spring collar and valve guide can only

be associated with th is fault.

Removing Valve Guides (All O.H.V. Engines)

All guides are a force fit in the head, and a suitable drift,

or hand press if available, is required for removal.

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FAULT LOCATION AND ENGINE SERVICING

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First, remove alt traces of burnt oil or carbon on the exposed

end of guide with emery cloth. With the head supported,

the guides are driven, or pressed, out and down into the port.

When dealing with alloy-type heads, first ascertain if a circlip is fitted, if so, this must be taken away for exhaustguide removal. This type of guide was introduced for the

1955 s e a so n a n d c a n be fitted to any alloy-type head, providing a new-type valve-spring seat is used. Alternatively, form a recess in sp rin g seat to clear th e radiu s of th e circlip. To remove the circlip tap the guide upwards, from inside the exhaust port, sufficiently for t he ci rclip to be removed, then deal with thi s gui de as previously described.

It is important that alloy heads must be uniformly heated before removing or refitting valve guides. If th is process is omitted, " scuffing " on the guide diameter in the head will occur, causing the guide to become a loose fit.

Refitting Valve Guides

To ensure t hat the guide is started squarely, pass t he valve through the guide hole, holding the valve with the fingers of one hand firmly against the head seating. With the valve firmly held, pu t the guide on the valve stem and press down hard to start the guide evenly and square, with the oil hole correctly aligned (see Fig. 2).

Th e head can be heated if necessary and t he guide pressed home. For protrusion length, see Technical Data at the end of this book.

Bent Push-rods

The information given under " Wear on Camshaft " also applies to trouble of this nature.

ENGINE NOISES

It should be mentioned that A.J.S. machines are manufactured with a high degree of mechanical silence. No manufacturer can produce an engine that will be devoid of mechanical noise throughout the whole period of the machine's life.

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In consequence, if a noise develops after considerable use, this does not necessarily indicate that the engine is worn out or that undue wear has taken place.

During use noises in some form or other will inevitably become manifest, which are audible only on account of the high degree of mechanical silence for which these models are noted.

It follows that, if mechanical silence is to be maintained,

replacement of certain parts is inevitable. This does not mean, however, that without such replacement, the engine efficiency o r reliability will be impaire d.

Big-end Rattle

After considerable mileage a rattle may develop, which is audible only when the engine is running light or not under load. The same noise w i l l also be aud ib le when the machine is rotating the engine, i.e., on a down gradient.

Th i s noise can occur when t he accumulated clearance of the crankpin, rollers and big-end liner reach a clearance of 0·0015 in. which is microscopical. The noise is audible only on account of the quiet valve gear used. The machine can be used for a further 5,000-10,000 miles without attention, but if the noise creates irritation, then this slight movement must be taken up.

In most cases a new set of big-end rollers will suffice, providing that the roller track on the crankpin or the big-end

liner is not damaged.

A.J.S. MOTOR CYCLES

Piston Slap

This engine noise, which is audible when the engine is under load or upon changing into a high gear, is entirely due to clearance between t he piston and th e cylinder.

On engines that have considerable mileage a rebore and oversize piston is the only remedy.

The use of the wire-wound piston undoubtedly reduces piston noise by reason of the close clearance permissible with

this t ype of pi ston. T hi s is, with new parts, 0·001 in. T his type of piston was introduced in 1948, after considerable

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experimental work with prolonged road tests under exacting conditions.

Construction of the piston is shown in Fig. 3, which illustrates the five turns of high-tensile steel wire used to control expansion. A Y-type alloy is used, with a tin-plated finish to minimise seizure. The shape is both oval and taper in

FIG. 3.—WIREWOUND CLOSE-FITTING PISTON.

Note the five turns of high-tensile steel wire used to control

expansion.

section, with the maximum around the gudgeon-pin bosses where the expansion is greatest. Therefore discoloration at these places is of no consequence . Owing to th e close clearance used, matching of pis tons and cylinders is carried ou t at th e factory, before asse mbly.

In addition, both cylinder and pistons are checked on a fluid gauge, with the dual purpose of avoiding manual errors and to ensure accuracy.

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Owners of machines mad e before 1947 can us e th is ty pe o f piston, providing that the short-type connecting-rod is fitted at the same time.

A table of tolerances with symbols stamped on both the cylinder-base flange and piston crown is shown in the Technical Da ta at th e end of t he book.

Engine noise due to piston slap will become inaudible when the ignition is retarded, and is not associated with a worn

small-end bearing.

Noise in Camshaft End-float

This is usually indicated by a " clacking " noise when the

engine is running at slow speeds, and disappears as engine speed increases. This is due to end-float of the camshaft (which drives the magneto) between the crankcase and timing cover. As the tappet is offset to the cam, this causes an oscillating movement of the cam, w hich is resp onsi ble for t he noise.

The origin of this noise can be proved, by running the engine

with the magneto chaincase cover removed until the noise develops, which will cease when pressure is applied on end of the shaft driving the lower magneto sprocket. A piece of wood or screwdriver handle can be used for this purpose.

To remedy, remove the magneto drive and timing-gear

cover, and then fit a 0·005-in. shim washer over the cam-wheel shaft, which will take up the play and stop the noise.

A.J.S. MOTOR CYCLES

Timing-gear Noise

Th is may be due to backlash between t he cam wheels and

the small timing-gear pin ion. T h e use of a n ew small pinion is first recommended, before incurring unnecessary expense in other replacements.

On ol d engines a worn timing-side axle bush or cam wheel

bushes will cause backlash, but it is rare for the cam wheel bushes to have undue, or premature, wear. The fact of inserting the cam into the bush and testing for rock is no guide as to wear, because of the short bush used.

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FAULT LOCATION AND ENGINE SERVICING

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Backlash between the camshaft which drives the magneto

and the small pinion can be detected as follows. Remove the

magneto chain cover and run the engine at idling speed to produce the noise which, if due to backlash, will become inaudible if the wooden handle of a screwdriver or similar tool is pressed down on the top run of the magneto drive chain. Th is load will damp down the backlash, thus proving t hat the noise is associated between these two p arts .

Noise in Rocker Box

Should a clicking noise develop in the region of the rocker box, on models fitted with hair-pin valve springs, this can be due to a disto rted sprin g making contact w ith the rocker box.

A similar noise will also occur if on e or both rocker arms are making contact with the valve spring. The spring will be marked with a slight groove.

To correct, grind a slight radius on the rocker at the point

where contact takes place.

When dealing with a distorted valve spring, try the effect

of changing its position, which may have the desired resul t.

Excessive end-play between the rockers and bearings for

rocker axles can be taken up by removing the rocker with its

shaft. The n tap out one of the bushes to the required amount so that no end-play exists, the rockers being free to move when the axle nut is tightened.

The two brass plugs in rocker box behind t he rocker arms are metering plugs, and should not be disturbed or the aperture increased.

Flywheel End-float

Th e flywheel assembly on all models is pulled towards the

engine sprocket by the shock-absorber spring. If the flywheels can be moved sideways by hand, and with the shock absorber assembled, this can be due only to the ball-races on the driving-side shaft being loosely fitting in the crankcase. This fault should be corrected promptly, to prevent further damage to the crankcase.

The cause of this occurrence is due to foreign matter

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entering the ball-races, temporarily locking the inner and outer member of the ball-race, which then rotates in the crankcase. If both ball-races are unworn or undamaged the outer members of each race can be copper plated to increase th e effective diameter and close up the interference fit. Both ball tracks must be masked with large steel washers before this process is carried out.

A.J.S. MOTOR CYCLES

FIG. 4.—METHOD OF CHECKING AMOUNT OF MOVEMENT

As an alternative, the crankcase half can be returned to the makers, who will knurl the bearing housing to close up the interference fit.

The crankcase should be uniformly heated to extract or refit these bearings. Wear on the two spacing washers between t he b ea ri ng is also due to t he same ca us e.

With the shock-absorber spring removed, it is possible to move t he fl ywhe els sideways, the n or mal end-float is between 0·020 in. and 0·025 in. (Fig. 4 shows the method of measuring end-float.)

BETWEEN FLYWHEELS AND CRANKCASE.

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FAULT LOCATION AND ENGINE SERVICING

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To prevent end loading the ball bearings after fitting, the inner race (flywheel end) should be tapped gently away from the outer race until both inner members are free to rotate individually.

Engines issued in the latter part of the 1952 season and on subs equen t models have two dissimilar d iameters in the ballrace housing. The outer race nearest th e sprocket is a close

interference fit and the outer race is a slight interference fit, which will facilitate bearing adjustment as previously described.

After fitting the later-type two-diameter timing-side bush check for end -floa t. If below t he specified a mount, face back the bush un til t his i s achieved.

ENGINE SERVICING

When to Decarbonise

Th e re i s no fixed or known distance th at th e engin e s hould

cover before decarbonising. With the advent of high-octane fuels now available the necessity for this work is not now so frequent. The need for this decarbonising is usually indicated by a fall off in engine performance, together with an increase in petrol consumption.

There is, however, a risk of damage to the exhaust valve,

and possibly the exhaust-valve seating in the cylinder-head, if th e engine is use d for a long mileage before decarbonising.

This is brought about by separation of additives in the fuel, which become impinged on either the valve or head seating. On combustion, the flame in the combustion chamber is forced through the small gap caused by the valve being held

off its seat, when burning will inevitably take place. A closely adjusted exhaust-valve push rod will have the same

effect,

It is in th e ow ne r' s in ter est to check com pre ssi on from time

to time after lon g mileage has been covered. Th i s check mu st

be made with the throttle wide open, otherwise the cylinder

will not be charged, and there is nothing to compress if the

throttle is closed or partially open.

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A.J.S. MOTOR CYCLES

Decarbonising the Engine

FIG. 5.—SPECIAL TOOL FOR VALVESPRING REMOVAL.

Inlet port. Oil-regulating

2. screw.

Inlet-guide oil-

3. feed passage.

Bolts fixing com-

4. pressor to

head.

Spring-com-

5. pressing bolts.

Spring tool

body.

Valve-spring

7. collar.

Valve springs.

Valve-guide

9. aperture.

A gasket set and valve-spring tool are required before commencing work. Proceed by removing the petrol tank, exhaust pipe with silencer attached, the high-tension cable and sparking-plug. Take out the throttle and air slides and protect them with a piece of clean rag. T i e thes e slides to the frame to p tube to prevent damage. Next remove the cylinderhead steady, if fitted, then the rocker-box oil pipe, using two spanners on both the union and union nut to stop the union moving when the nut is released. Disconnect the valvelifter cable, if fitted, to the rocker box.

Unscrew all bolts fixing th e rocker box to the cylinder-head and remove, with the exception of the two bolts below the frame rail. The rocker box can now be tilted and moved to the righ t side, when the push rods can be extracted. Identify these rods for location, they will interchange, but it is best to replace them in t he original position.

The four cylinder-head bolts are next removed, when the cylinder-head with push-rod tubes attached can be taken

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FAULT LOCATION AND ENGINE SERVICING

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away. Draw out, in turn, each push-rod cover tube and watch for two th in steel dished washers, which may be fitted over these tubes.

With the cylinder-head on the bench, both valves can be

checked to decide if grinding is necessary by wiping dry the combustion chamber, th en nearly filling each po rt with pet rol in turn. If the petrol does not seep past the valve seat after standing for a short while, the seating must be in order. It is also worthwhile making this check after valve grinding.

A gas-tig ht jo in t between the valve and its seating is all that is required, and if petrol does not seep past the valve a gastight joint will be ensured.

FIG. 6.—ALTERNATIVE TYPE OF TOOL TO THAT SHOWN IN

Valve collet.

and 3. Spring collar.

Fulcrum bolt.

FIG. 5 FOR VALVE-SPRING REMOVAL.

Spring compressor.

Oil passage from rocker box. Oil-regulating screw.

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28 A.J.S. MOTOR CYCLES

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If the valves have to be removed, first remove all traces of carbon in the sphere of the head, with a tool such as a 6-in. steel ru le, before the valves are taken o ut. T hi s will preve nt particles of carbon lodging in the ports, which is difficult to extract unless a compressed-air line is. available.

Valve Grinding

Two ty pes of valve-spring tools are s hown in Figs. 5 and 6

for use on engines fitted with hair-pin valve springs. Coil-

type springs can be removed with a spring compressor such as is made by Messrs. Terrys. With both valves removed, the small amount of carbon round the valve seats ca n now be dislodged.

Avoid unnecessary valve grinding for, on alloy-type heads, the valve seats are not replaceable. If the exhaust valve is burnt or badly pitted it should be reseated by a dealer with suitable e quip men t; the seat angle is 45 °. A piece of rubber tub ing slipped over the valve end will serve as a tool to grind the valve to it s seat. Do not u se a rotary moti on during this process, which will make continuous lines on the valve, turn the valve 180° each way until a matt surface is seen on the valve and seat.

Avoid handling the valve with grinding paste on the finger and thumb as the paste can get into the guide and set up a lapping process when the engine is first run on reassembly. After grin ding and removing all traces of g rinding compound, pass a piece of fluff-proof rag through both guides. Squirt oil through both oil passages, apply oil on both valve stems and reassemble both valves. The head can now be placed aside.

It is not advisable to disturb the piston rings unless absolutely necessary. Springing the rings open to clear the ring

slots will distort them, particularly if pieces of tin or sheet

foil are used for this purpose,

Removing Loose Carbon

If the cylinder barrel is not to be removed, rotate the engine until the piston is on top dead centre, then with the

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use of the tool previously described, carbon formed on the piston crown can be removed. During this process particles of carbon will collect in the recess formed between the piston top lands an d th e bar rel .

To remove, set th e engine with the piston about 1 in. down the barrel. Press some grease into the recess between the piston and barrel, turn the engine past top dead centre and down the cylinder again to the extent of 1 in. A ring of

grease will be formed in th e cylinder barrel, with particles of carbon adhering to it, which can be wiped off. Repeat this process to ensure all loose carbon is removed.

Replacing the Cylinder-head

The cylinder-head can now be replaced in the following

mann er. F it new sealing rubbers in the push-rod cover-tube apertures with the metal washers on each side of the sealing rubbers, then insert both tubes in the head. If new rubber seals are not fitted, some jointing compound on the reduced ends of both cover tubes will tend to prevent oil leakage.

Engines fitted with a solid head gasket can use the original gasket, if it is annealed before fitting by heating until the gasket is cherry red, when it should Be plunged quickly into cold water to make the metal ductile.

If this gasket is damaged or if there is ovality in its bolt holes, this means that the gasket has been leaking. In this case, it should be discarded.

Care should be exercised when fitting the gasket into position, ensuring that it is correctly located, as it might move

when the head is replaced.

Before attempting to tighten the cylinder-head bolts, turn

the engine to top dead centre of the firing stroke (i.e., both tappets down) and tighten the four bolts diagonally. In factory service a torque spanner set to 36-40 ft.Ib. is used for

this purpose.

Whilst it is essential that these bolts are tight, over-tightening, particularly in the case of alloy-head engines, ca n str etch these bolts or possibly break them if undue force is used.

Great care must therefore be taken when replacing alloytype cylinder heads.

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Refitting Rocker Box

A new rocker-box gasket is recommended. On engines made before 1949 this can be incorrectly fitted in reverse. This seals the oil passage in the cylinder-head, which lubricates th e inle t valve. S qui rt oil on t he valve ends , inse rt th e

centre bolts in the rocker box and offer up both push rods,

engaged with the rocker arms. Check the position of the engine, as if one or both tappets are lifted strain will be imposed on the rocker box during the process of retightening the

fixing bolts.

Replace the components in the reverse order to that given for removal. In the case of the exhaust pipe, this should be cleaned, particularly underneath, using a chrome cleaner.

Wi th an alloy head, if the exhaust pip e is not a good fit in the port, a rattle can occur when the engine is hot, due to movement of the pipe, which is sometimes difficult to d etect.

To re medy, a steel drift, shaped like a carrot, can be driven into the top end of the pipe, making it slightly bell-mouthed and a closer fit when it is replaced.

A.J.S. MOTOR CYCLES

Cleaning the Carburetter

Dismantle the carburetter completely. To clean out the float chamber, if the choke or brass jet block is difficult to remove use a piece of suitable wood on the top end of the block and ta p th e end of the wood lightly a nd gently, to avoid distorting the block, which will make it useless. Clean out th e small hole drilled in t he brass j e t block or choke (see F ig.

20) an d also the hole drilled diagonally in th e mixing c ham be r, whic h is equally im portant as the pilot jet (see page 57).

The flange on the mixing chamber may be buckled. In order to check this, place a straight-edge or steel rule on the flange when, if held up to the light, distortion can readily be seen. A piece of emery paper on a sheet of glass will serve as a surface p late so that the flange can be rubbed down until it i s perf ectly flat, preventing an air leak. On carburetters tha t are not fitted with a Hycar ring it is essential to use a thin paper gasket on this joint, as a thick one will caus e the carburetter flange to bend when the two stud nuts are tightened.

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When the carburetter has been reassembled, work the throttle several times, making sure the slide does not stick or is sluggish, due to a distorted mixing chamber, before the petrol tank is replaced.

Push-rod Adjustment

It is most important that any moving part of the engine should not be replaced dry. Apply oil to b oth pus h-rod ends before making this adjustment.

As quietening curves are used on both cam flanks, correct push-rod adjustment can be effected only with the engine properly positioned. These curves are slight ram ps , designed to close up rocker clearance slowly when the valve is lifted, with the same effect when the valve closes. Therefore, both tappe ts must be on t he base circle of the cams to be clear of

these ramps. This position is when the piston is on the t op dead cen tre of the firing stroke.

On engines with iron head, adjust the pus h rods when the engine is cold, so that there is no appreciable up-and-down movement in both push rods, the rods being just free to rotate

with the fingers. With an alloy-type cylinder-head, run the

engine until it is reasonably warm, to offset expansion, and

make the adjustment in the same manner as with an iron

head.

Th e use of a test tank is worthwhile. Th is may consist of a qua rt oil t in, with a union soldered in the bo ttom to accommodate a petrol pipe, and attached to one of the frame tank rails. The engine can be ru n for a short while, to settle down,

when it may be necessary to reset the push rods and retigh ten th e rocker-box bo lts before the petrol tank is refitted. Do not overtighten the nuts on the rocker cover.

Refitting the Petrol Tank

Before refitting the tank, make sure that the cylinder-head

steady nu ts are very firm ly tigh tened. Loo k underneath the

tank for evidence of rocker-box oil pipe fouling, and set this pipe as required.

Ensure that there is no dirt in either of the petrol-tap re-

cesses. Arrange the control cables on the frame tube neatly

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and then refit the tank. Do not forget to wire the petrol-

tank bolts, which should not be unduly tightened, to allow th e

tank to flex slightly.

Checking Ignition Timing

This is an important setting, and should be carefully carried out. With high-octane fuels it is possible to run with excessive ignition advance without audible detonation or " pinking ", which must have an adverse effect on bearings, particularly the big-end assembly. Therefore, the maker's recommended setting should be used.

An alteration in the contact point gap affects the ignition timing. Increasing the gap advances the timing, and, conversely, closing the gap retards this setting. It is important to set the contact points to have a gap of 0·012 in. before checking

or setting the magneto timing. Proceed by removing the rocker-box cover, sparking-plug and contact-breaker cover. T ur n t h e en gin e u n t i l t h e i n l e t valve op e ns, t h e n cl o s es ; check piston position by inserting a piece of old wheel spoke, or something similar, through the sparking-plug hole. Hold the wir e as vertical as possible, and if top gear is engaged t he rear wheel can be rocked to and fro, when the wire will rise and fall as the piston passes the top-dead-centre position. When

the wire is at the highest point of its movement the piston is then on top dead centre.

A.J.S. MOTOR CYCLES

Make a mark on the wire to register with the seat on the

cylinder-head for the sparking-plug. Take out the wire and

make a further mark ½ in. higher up the wire, which is the max imum advance recom mende d. H ave available a piece of cigarette paper which is inserted between the contact points, fully advance t he ignition control lever, or if an auto-advance un it is fitted, make a small wooden wedge to j am the unit in this position. Put the wire through the plug hole, again as vertical as possible , turn the engine backwards until the higher of the two marks on the wire register with the plug seat, when the contact points should be jus t about to separate. A light pull on the paper will indicate exactly when the points separate.

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FAULT LOCATION AND ENGINE SERVICING

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FIG. 7.—ROTATING OIL-PUMP PLUNGER.

Inset shows the guide screw which registers in the plunger profiled

groove, thereby providing the reciprocating movement.

Dowel peg, locating timing-

1. gear cover.

Timing-side flywheel axle

with integral gear for driv-

ing oil-pump plunger.

Oil-pump plunger.

3. Screw (one of three).

4. Guide pin.

Screwed body for guide pin. Guid e pin in position engaged

7. in profiled cam groove of plunger.

Ta pp ed hole (for oil-feed pip e

to pump).

Tapped hole (for pipe return-

ing oil to oil tank).

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Setting Ignition Timing

If t he magneto timing has been disturbed, it is best to leave

the sprocket on th e camshaft loose.

To remove t his sprocket with drive assembled, unscrew the fixing nut a few turns then with use of a tyre lever, with one end bent at right angles, placed behind the sprocket, it can be levered off. If the sprocket proves stubborn to remove, maintain pressure and tap the shaft end lightly, the jar in

doing thi s will release the sprocket. Details given for check-

ing this setting are used for resetting.

Note that the nut securing auto-advance units is self-extracting and the assembly will be withdrawn from the armature shaft as the n u t is unscrewed,

Lubrication System

The oil pump on both late 1939 models and also models subsequent to 1946 are practically identical as rega rds design. The pump has only one moving part—the double-diameter plunger. Th e plunger is rotated by worm gear on the timingside flywheel axle, the p ump action is created by a reciprocating movement, due to the guide pin operating in a profiled groove cut in the larger diameter of the pl unger. Numerous cases are known where the oil pump has been damaged—and in some cases the crankcase as well—by inexpert attention due to incorrectly locating the pump guide pin (see Fig. 7). No other attention to this part of the engine is needed except to check the guide-pin sleeve for tightness.

A.J.S. MOTOR CYCLES

Oil Filters

Up to 1956 a close-grained felt filter was used in the oil tank to separate foreign matter during the passage of oil from the su mp to the tank.

A magnetic filter is used in place of the fabric type on the

1956-57 engines. A metal gauze or strainer is fitted to the

oil-feed pipe to prev ent rag particles or pieces of fluff e nte ring the feed side of the oiling system.

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Cleaning the Filter

After engine over hauls, and after the first 500 miles the oil

should be changed and the filter cleaned at the same time.

Once the interior of the engine is clean, it is not essential to clean the filter at frequent intervals, in which case the mileage for the next cleaning should be between 5,000 a nd 6,000 miles.

After draining the oil tank, the engine must be run for several minut es before oil is seen eme rgin g from th e spo ut i n the oil tank. If this compartment is filled with oil it s re tur n

will be accelerated.

PERIODICAL MAINTENANCE

DAILY. Inspect and check oil circulation.

WEEKLY. Check oil level in tank. Check tyre pressures. EVERY 500

Check front chaincase oil level. Check the battery for electro-

lyte level (see instructions in battery lid) and avoid overfilling.

EVERY 1,000

1938-47. T op up oi l-type gearbox if re quir ed. G reas e rear

chain (see List of Lubricants, page 165). Grease h ub b earing lightly. Grease brake-expander lever. Grease steering-head bearings. Grease brake pedal. Oil moving parts, such as rear-stand bolts when fitted. Oil control cable revolving nipp les. Oil b rake-le ver clevis pi n. Oil con trol cable when

nipples are fitted.

EVERY

filter. Check steering-head bearings. Check push-rod ad-

justment.

EVERY 10,000

by Lucas Service Depo t

MILES.

5,000

Check gearbox oil level, 1948-57 mode ls.

MILES.

Ad d 2 oz. grease to gearbox—models

Change engine oil. Clean oil-tank

Ha ve magneto and dynamo serviced

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CHAPTER II

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ENGINE OVERHAUL

HE information given in this ch apter cover s the complete dismantling, overhaul and reassembly of the engine.

Certain changes have been made on engines produced since 1947, and for the benefit of the readers, these have been

summarised in tabular form on pages 38 and 39.

If a complete engine overhaul is co ntemplated, and to ensure that the work can proceed smoothly and without delay, some thought should be given as to the equipment th at is likely to be required. If workshop facilities are available no difficulty should be experienced if the dismantling and assembly are carried ou t methodically an d without undue haste. Whilst it is only natur al to end eavour to complete th e work as quickly as p os si b le , " r us h i n g th e job " ca n lead to d is a ppointment and delay. Cleanliness in work is vital, the bench, tools and equipmen t mus t be free from road g rit or abrasive.

A table of spanner sizes is given in Chapter IX and also a list of special tools. In addition, it is necessary to have a valve-spring compressor, plenty of clean rag, a clean paintbrush (to apply oil to engine parts), a petrol and oil squirt, grinding paste, jointing compound, i.e., " Wellseal " an d a Spa re Pa rts list. A met al t ray made from perforated zinc is most useful to wash small pa rts, when immersed in paraffin.

DISMANTLING THE ENGINE

Start by following the instructions given for decarbonising the eng ine (see page 26), b u t leave t he cyli nde r attached to the crankcase. Remove the battery. Place a tray under the chaincase to catch oil when t he outer porti on is removed.

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Removing the Engine

Th e dynamo chain is endless and is removed, toget her with

the engine sprocket, to be dealt with later.

Straighten the lock-washer, prise out the circlip from the

nut for the dynamo sprocket, apply a spanner on t he two flats

FIG. 8.—TOOL FOR CLUTCH-NUT REMOVAL.

machined on t he back of t he sprocket to p revent b ending t he

armature shaft and unscrew the shaft nut, leave th e sprocket

in position.

Next, turn to the engine-shaft shock-absorber fixing nut, which can be difficult to unscrew. Th e hexagon for this nut is shallow, therefore the ring span ner must be a close fit, for if the hexagon is damaged it will be next to impossible to unscrew

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A.J.S. MOTOR CYCLES

ENGINE DESIGN CHANGES

1947 MODELS

(1) Improved type oil-pump plunger (two-start type) with new

timing-side axle (identified by 2S stamped on plunger).

(2) Oil-feed passage in timing-side half crankcase increased to

9/32 in. diameter to prevent cavitation, with corresponding increase in diameter of the oil pipe, (3/8 in. diameter).

(3) A two piece oil pum p guide pin 3/16 in. in diameter to prevent

wear on the pin due to the increased plunger speed.

(4) Shorter connecting-rod (see " Technical Data ", page 178,

for centres).

(5) The use of a long plain bush for the timing-side bearing;

the small roller bearing is now obsolete. Engines fitted with the old-type bearing can use a modified bush w ith two external diameters. The steel sleeve is retained to locate the new bush on the large external diameter.

1948 MODELS

(1) Annular groove in pu m p plunger increased from 3/1 6 to ¼ in.

diameter with suitable guide pin. (2) Wire-wound pistons fitted to 500-c.c. models. (3) 500-cc. type high crankcase used for 350-c.c. models after

engine number 8000. (4) 500-c.c. flywheels used for the 350-c.c. model. (5) Larger brakes (7 in. diameter).

1949 MODELS

(1) New-type cylinder-head, with hair-pin valve springs with

rocker box to suit. (2) Valve lifter transferred from crankcase to rocker box. (3) Wire-wound pistons for all models. (4) Longer valves, hardened valve end caps discarded. (5) N ew rockers for longer valves, also new valve guides .

1950 MODELS

(1) Alloy cylinder-heads and barrels used on Competition

models only. Steel crankpin washer in place of bronze type.

1951 MODELS

(1) Alloy cylinder-heads used on both touring-type engines.

Crankpin washers discarded, flywheels altered.

1952 MODELS

(1) Open-tray valve-spring seat, prongs for valve springs in-

creased in length.

(3) Cylinder barrel lengthened 1/8 in. on 500-cc. touring engine,

compression plate discarded.

(3) Recess for driving-side bearings in crankcase with two

diameters, for close and easy interference fit to avoid " end loading " of these bearings.

(4) Top compression ring chrome-plated.

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ENGINE OVERHAUL

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ENGINE DESIGN CHANGES—continued

1953 MODELS

No change.

1954 MODELS

(1) Oil feed in rocker box modified to increase oil supply to

rocker end of inlet valve and stop valve-spring wear. (2) N ew rockers for valve end s wit h groove in side for oil du ct. (3) High-lift cams. (4) Larger-diameter timing-side shaft, wit h flywheel to suit, (5) Two-diameter timing-side bush, steel sleeve discarded. (6) Automatic ignition control on 500-c.c. model.

1955 MODELS

(1) New crankcase to use one small and one large driving-side

bearing. (2) New driving-side flywheel (keyways at 180°). (3) Circlip fitted to exhaust-valve guide.

1956 MODELS

(1) Cylinder-wall oil feed discontinued. (2) Compression ratio increased to 7·5 for 350-c.c. models, 7·3

for 500-c.c. models. (3) Oil -ta nk felt filter deleted an d magnetic filter fitted in crank-

case.

1957 MODELS

(1) Engine-shaft shock absorber discarded, shock absorber in-

corporated in the clutch assembly. (2) A.M.C. gearbox on all models. (3) Improved detachable rear-wheel design. (4) Girling rear suspension units introduced.

it with a spanner. Turn the engine against compression,

apply the sp anne r and give th e free end a series of light blows

with a hammer. Using leverage will only close up t he shock-

absorber spring. If the nut resists removal, engage top gear and press on the rear-brake pedal and try again. Loosen the nut and remove the clutch, by detaching the clutch-spring nuts , the springs and cups, then the pressure plate. Straighten the shaft-nut lock-washer, engage top gear or use the tool

shown in Fig. 8, then unscrew the mainshaft nut. Take out the front-chain connecting Link, remove the chain and refit the link to avoid loss. Pull the clutch assembly away from the

mainshaft and watch for twenty-four loose rollers in the clutch

bearing.

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Separate the dynamo sprocket from the armature with the tool shown in Fig. 9 placed between the back of the sprocket and the dynamo body. One or two light blow s with a hammer, on the end of the spanner, will dislodge t he sprocket. T ake away the engine sprocket, shock absorber, dynamo chain and sprocket, take out also the distance piece behind the engine

sprocket in case it becomes misplaced.

A.J.S. MOTOR CYCLES

FIG. 9.—TOOL FOR REMOVING SPROCKETS FROM MAGNETO

Remove the bolt connecting the battery strap attached to

the rear portion of the chaincase. Straighten the three tabwash ers a nd u nscr ew t h e thr ee bolts fixi ng the chaincase to the en gi ne. Th e s e bol ts ar e an " odd " size—0·321 i n. across th e flats. Take off the nut on the central chaincase bolt and identify the distance piece under the nut. If the engine

number is after 8000 tap out the chaincase bolt and identify

the distance piece on it. The rear portion of the chaincase

can be removed.

Drain the oil tank, take off the magneto chain cover, the two magn e t o sprockets and chain (see details on " ignition setting ", page 32). Remove the screws fixing the timing cover to the crankcase and tap off the cover. Identify location of these screws. Disconnect the magneto control cable, handlebar end.

Wheal th e oil tank is empty remove the two oil pipes, tank

and engine end. When releasing the top oil-pipe union from

the crankcase me extreme care to avoid the spanner jamming

AND DYNAMO.

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against the lower oil union, which can break away the union

boss and ruin the crankcase beyond further use.

Remove the magneto platform with the magneto on it, with the front engine plates. Disconnect the valve-lifter cable (early engines) also the rocker-box oil-feed pipe. Take out all bolts passing through the crankcase and frame and slack off t he gearbox fixing bolt s.

Grasping the cylinder, the engine can be lifted up to clear the rear engine plates and taken out of th e frame. It may be necessary to spring outwards the front frame down tube a trifle to clear the crankcase.

Removing the Piston

After lifting the cylinder barrel and compression plate (if fitted), the pist on is ta ken off by using special circlip p liers for

compressing and removing one of the circlips. The gudgeonpin is a sliding fit, which if difficult to extract may be due to a burr caused by the circlip groove. It is best to remove t his burr with a pointed scraper, in preference to driving out the gudgeon-pin, to avoid distorting the piston.

Pistons of the wire-wound type are made to very close limits,

and should be handled carefully.

Separating the Crankcase

Firs t, clean off all traces of road g rit and d irty oil from the bottom of t he crankcase before it is placed on the bench, A wire brush is recommended for this purpose, with a paraffin wash to follow.

Any attempt to separate the crankcase before removing t he oil-pump plunger will result in serious damage. Remove front and rear oil plunger end caps, together with the guide screw, w hic h is shown in F ig , 10.

Next, unscrew th e nut fi xing t he small timing pinion, which has a left-hand thread. T h e small pi ni on has a t ape r bo te and needs a tool to remov e it (Par t No . B.2151).

Remove the botto m small crankcase bolt, if fitted, a nd then crankcase can be parted.

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FIG. 10 (above). — GUIDE

SCREW FOR OIL-PUMP

PLUNGER.

FIG. 11 (right).—METHOD

OF SEPARATING FLYWHEELS.

Checking Big-end Assembly

Before testing for up-and-down movement between the connecting-rod and bearing, squirt paraffin or petrol through holes in the timing-side axle, preferably by placing on this shaft an old gudgeon-pin bush, to wash away oil in the assembly. Any slight movement will th en be apparent The

oil acts as a cushion, preventing play being detected. This is why big-end noise is not audible when the engine is cold. Connecting rod side play should be approximately 0·010 in.

A.J.S. MOTOR CYCLES

Separating Flywheels

The centre shaft for the crankpin is slightly tapered and a

force fit in the f lywheels. An arbor press, or separating tool

as sho wn in Fig . 11, i s needed to pa rt t he flywheels when t he crankpin nuts are removed.

Removing Main Bearings

On all engines made from 1938 to 1954 the two driving-

side shaft bearings are identical in shape and size. Up to

1952 b o t h b ea ri ng s s hould be a close fit in th e crankcase an d a

sn ug p ush fit on th e shaft. Fr om 1952, th e bearin g housing

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has two dissimilar diameters as described in " Flywheel End Float " (see page 23).

On all engines the crankcase should be uniformly heated to remove these bearings, with aid of a plain drift, 1¼ in. in diameter, with the crankcase supported on the inside with a piece of tube, not less than 2½ in. in diameter. The bearing spacing washers will come out with t he bearings.

Removing Cam-wheel Bushes

These bushes are a press fit. Use a drift with a pilot 0·495 in . In diameter by ½ in. long (the handle is 9/16 in. in diameter a nd 4 - 6 in . long) to drive ou t t he metal cup covering the cam-wheel bush, which is also a press fit. With the cover supported, dr ive out the ca p w i t h a 7 /1 6 in . d r i ft.

Removing Timing-side Bush

On engines fitted with a short bush and roller bearing, the

bush is forced out from inside the case with a tube to support

the case placed round t he bearing box inside the timing gear. This tube should be 1½ in. outside diameter and 1¼ in. internal diameter. Where a double-diameter bus h is used, obviously these are pressed out from inside the timing cover with the crankcase suitably supported on the inside.

Connecting-rod Service

Thi s r od uses a detachable liner, replacements are made to

a " spares " size to allow for contraction. Even so, correct

FIG. 12.—LAPPING TOOL.

concentricity cannot be guaranteed, as contraction varies with different rods. It is therefore recommended to send th e rod to the factory for a service exchange, as the liners in t his type

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of rod are ground after fitting. A new small-end bush, which is also ground, is fitted in a ddition to the new liner.

Whe n it is not possible to have the rod exchanged a lapping process is neces sary to ensure concentricity, by using a lapping tool, as shown in Fig. 12, obtainable from the makers (Part

No. A8078). A mixture of paraffin and grinding paste is the lapping medium used.

For the best results th e rod, after fitting t he cage and rollers,

should just go over the rollers, with no side rock in the rod.

Selective assembly is used in the factory for new engines.

The lapping process is required only when the rod is stiff

to rotate after fitting, or the rod will not pass over the rollers.

Removing Flywheel Shafts

Both shaft nuts are right-handed, the driving-side shaft is parallel and a force fit. On engines made up to 1954 the timing-side shaft uses a taper. Engines made after this date have a larger-diameter shaft, which is parallel in the flywheel. An arbor press should be used for removing these shafts.

A.J.S. MOTOR CYCLES

Dismantling the Rocker Box

The general arrangement of the rocker-box assembly is shown in Fig. 13. Each rocker assembly is built up with an

FIG. 13.—ARRANGEMENT OF ROCKER-BOX ASSEMBLY.

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axle, bearing sleeve, two rocker arms and two fixing nuts and

washers. The axle is a loose fit in the sleeve, which is inten-

tional, as the axle is gripped on the sleeve when the fixing nuts are tightened.

To dismantle, remove the axle nut securing the valve rocker the axle with the push-rod rocker can then be withdrawn. The steel sleeve is then extracted, or it may come out with the axle.

It will be observed that a felt sealing ring is situated between both rocker bushes, which also acts as an oil distributor. This can be lifted out with a sharp-pointed tool. Rocker bushes can be tapped out with a drift 0·490 in. diameter.

Engine-nut Sizes

These details are provided to enable the operator to collect the necessary tools before starting work. Measurements shown are taken across the flats of the nuts and bolts, so that spanners can be checked by measurement.

Nut size, in.

. . .

1/4

. . .

Engine and

frame bolts

S A nut Clutch nut (old type) Clutch nut (late type) Front chaincase retaining bolt Timing-pinion nut

5/16

. . .

3/8

. . .

7/16

. . .

3/8

. . . .

. . .

spanner, in.

Standard

Whitworth

3/16

1/4

5/16

3/8

3/8 9/16 9/16

3/4

2 B.A.

3/8

Spanner

size across

flats, in.

29/64 17/32

19/32 45/64

45/64 1 1/64 1 1 3/16

21/64

45/64

Tappet-guide Removal

Both guides are a force fit in the crankcase. With engines

made from 1938 up to 1948, the valve-lifter shaft must be

extracted before the exhaust guide can be removed. A tool

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FIG. 14.—TAPPET-GUIDE REMOVING FIXTURE.

The fixture is screwed to the crankcase, the projections entering the camshaft bushes in the crankcase. By turing the squares with a sp anne r, t he t appe t guides a re pres sed u pwa rds t o remove t hem .

A.J.S. MOTOR CYCLES

used for this purpose is shown in Fig. 14. Wi thout the use of this tool the crankcase must be uniformly heated, then the gu id e s wi th th e ta p pe t s as se mb l ed can b e d ri ve n up w a rd s from inside the timing-gear ch est It may also be necessary to heat the crankcase when the removal tool is used if these guides resist moving.

As these parts are not prone to wear, they should not be

removed without good reason or unless wear or damage to the foot of the t app et has occ urred (see " Cam Wear ", page 17).

If modification is to be effected by fitting multi-groove guides the exhaust guide must be slotted as shown in Fig. 15 for

valve-lifter operation on engines made before 9310 (350-c.c.)

and 8765 (500-c.c).

To dismantle the guide, use a screwdriver to expand the

collar clear of the tappet groove, when the tappet can be pushed out.

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Before removal note the position of these guides in the crankcase, s o t h at the replacements a re mad e in th e same location.

Replacing Flywheel Shafts

In the event of fitting new shafts, extreme care must be

exercised in correctly locating the timing-side shaft, otherwise

the valve timing will be affected. Incorrect location may also cause damage to the oil pump and worm on the timing-side axle, by partial or total restriction of the oil feed to the bigend, due to the oil hole in the shaft and the flywheel not being in complete register.

To ensure correct location if the locating tool as shown in Fi g. 1 6 is not available, draw a pencil lin e o n the tape r of th e shaft passing through the centre of the oil hole drilled in the

shaft. Offer up the shaft so that the pencil line registers exactly with the oil hole drilled in the flywheel. Press the shaft firmly home and then tap the pinion end of the shaft with a rawhide mallet or similar tool to drive t he shaft home

FIG. 15.—SHOWING POSITION OF SLOT IN TAPPET VALVE.

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FIG. 16.—SHAFT-LOCATING FIXTURE.

on its taper to prevent it moving when the fixing nut is tightened. As a taper is used, do not use undue force in tightening the nut. On early-type engines, position the nut so that the lock-screw can be fitted.

A.J.S. MOTOR CYCLES

REASSEMBLING THE ENGINE

Details in this chapter apply to all engines made from 1938

to 1958.

Flywheel Assembly

Assuming the flywheels have been completely dismantled, commence the assembly by first fitting the timing-side axle in correct location as previously described. Next, fit the driving-side axle and firmly tighten the fixing nu t . Take up th e crankpin, squirt oil through the hole drilled in the centre shaft, to ascertain that the oil drillings are free from obstruction.

Scribe a pencil line on the centre shaft passing through the oil hole, insert the crankpin and washer if fitted in the timing-side flywheel, when the shaft can be pressed into the flywheel against the face on the centre sleeve. Place on

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the crankpin the roller cage, fit thirty rollers in the cage slots, apply clean oil, place th e oth er crankpin washer (if fitted) over the crankpin. Offer up the driving-side flywheel and roughly align both flywheels with a straight-edge or steel

rule.

To rely on t he shaft-nut pr essure is unsatisfactory, for unl ess both wheels are pressed firmly against each shoulder of the centre sleeve for rigidity the flywheels will flex under load, which in time will result in a fracture of the crankpin centre shaft.

Therefore, the use of an arbor press is essential for this

work.

As the centre shaft is movable, the crankpin nuts should be run down evenly, otherwise the centre shaft will be pulled through the sleeve during the process of tightening the crankpin nuts.

In factory service a torque spanner set to 190 ft.lb. (220

FIG. 17(a).—FLYWHEEL ASSEMBLY—1945/54 MODELS.

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A.J.S. MOTOR CYCLES

FIG. 17(b).—FLVWHEEL ASSEMBLY—1955-57.

ft.lb. for special Scrambles models) is used to tighten both crankpin nuts.

A further check of the oil passages should be effected as described in " Choked Big-end Feed " (see page 14). After finally tighte ning bot h crankpin nuts, flywheels are set to run true with a maximum error of 0·001-0·002 in. check ed between centre s with a gauge on the shafts as close to th e flywheel face as possible, to record the maximum error.

Crankcase Assembly

When fitting a new timing-side axle bush the chamfered end of the bush is inserted in the crankcase to facilitate entry and location. Although the finished bore size is made for replacements, contractions on this bush will occur when in position, dependent on the interference fit of this bush in the crankcase. The bush must therefore be reamed to size (see

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"Technical Data", pages 181 and 182), as insufficient clearance between the bush and its shaft will result in a seizure.

In production, this bush is " fine bored " on a special

machine designed for the purpose.

Insufficient flywheel end-float can cause a " thumping

noise " under load with the risk of a seizure.

Refitting Driving-side Bearings

Uniformly heat the crankcase half to facilitate assembly. T h e position of bearing spacing washers is shown in Fig. 17, A pilot drift is shown in Fig. 18, which will centralise the spacing washers whilst the outer bearing is pressed home. See details on " Flywheel End-float " to avoid end loading bearing s when in posit ion. 1955-57 engines use one spacing washer between the be arings.

Refitting Camshaft Bushes

The four bushes used have a chamfer on one end, and must be p ushed in with t he chamfered en d f irst . T h e bu sh fo r the cam wheel which drives t he magneto in the timing cover has a spiral groove machined at one end, to stop oil pumping into the magneto chaincase cover. This bush must be fitted with the oil groove on the outer end of the bush, nearest the magneto drive sprocket. Bushes will need reaming after fitting (see " Technical Data " for size). These bushes are identical on all models.

To ensure correct alignment, firmly fix the timing cover to the crankcase and use a pilot reamer as shown in Fig. 19.

After reaming, camshafts can be fitted to test for free move-

ment and also for end-float; this should be nil.

Refitting Tappets and Guides

Th is operatio n should be carried out when the crankcase is bolted together for rigidity. The tappets inserted in the guides are driven downwards from the crankcase face until the

large diameter of the guide is flush with th e crankcase.

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A.J.S. MOTOR CYCLES

FIG. 18.—PILOT DRIFT FOB BEARINGS.

FIG. 19.—DIMENSIONS OF PILOT REAMER USED IN REFITTING

CAMSHAFT BUSHES.

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Reassembling the Crankcase

Apply some clean oil on the bearings in the crankcase. Locate the bearing separating washers, fit the driving-side on to the flywheels and press the case home. Invert the flywheels, apply jo int ing compound on th e crankcase face, if " Wellseal " is used allow th e com pound to become " tacky " before fitting the other portion of the crankcase. Put at least three bolts through the crankcase temporarily, including the small one at the bottom.

See t h at b o th crankcase halves are in register on t he face for the cylinder before the bolts are tightened, to ensure an oiltight joint. Fit the piston with care, to locate the circlip, wit h t h e sp li t in t he s kir t facing t he front. Space the pistonring slot at 120° to each o ther. T ake up the cylinder, stick a paper washer on to the cylinder base, wipe the bore with a piece of fluff-proof rag an d oil the piston. Raise the piston

and put a piece of clean rag under it, in case a piston ring breaks when fitting the cylinder. Carefully fit the cylinder, closing in the rings with one hand until the piston has entered th e b a r re l . T a k e away t h e r ag from under the piston and lower the barrel on to the crankcase. Screw down the base nuts diagonally and tighten firmly.

Fit the small timing pinion and nut {left-hand thread). Overtightening this nut can split the pinion. Fit the cam wheels as already described. Copiously oil the oil-pump plunger and move the plunger to and fro whilst the guide pin is fitted to ensure the pin is located in the plunger groove. Apply a little jointing compound on the pum p end cap s before fitting. Take out the bolts temporarily fitted through the crankcase, pu t some clean rag over the cylinder and get the frame parts cleaned. Th e n refit the engine back int o the frame.

Refit the parts removed in the reverse order described for dismantling, not forgetting to refill the oil tank when the oil pipes are replaced.

Fitting Special Camshafts

Both the high-lift and racing-type camshafts can be fitted to all types of engines. On early type engines the boss

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surrounding the timing-side bush must be machined to provide clearance for the higher lift of these camshafts. If the engine is dismantled this is an opportune time to deal with the crankcase and check these shafts in position as described

in " Refitting Camshaft Bushes " (see page 51).

Engines fitted with a valve lifter in the crankcase will need

an alteration to the valve-lifter shaft, by grinding the flat which makes contact with the split collar on th e exhaus t tappet, see Fig. 47. Omission to do this will result in the exhaust tappet being held off the base circle of the cam, causing incorrect valve clearance and valve timing.

The valve motion must also be checked when these cams are used, particularly on engines made before 1954. For details on checking see " Wear on Camshafts " (page 17).

Types of Special Camshafts

High-lift cams are marked with the letters HL etched on one side of the cam flanks, and are designed to increase the volumetric efficiency of the touring models.

Racing camshafts are marked SH, and are designed for a straight-through exhaust-pipe system. There will be a loss of power if these cams are used on a machine fitted with a silencer.

Fo r valve timing see details on Scrambles models (Chapter VII).

To obtain the full benefit of these camshafts, a slightly larger bore carburetter is recommended, namely 1 1/16 in. for the 350-cc. and 1 5/32 in. for the 500-c.c. models.

A.J.S. MOTOR CYCLES

Increasing Compression Ratio

Now high-octane fuels are available the compression ratio on models made before 1956 can be increased to 7·5 for the 350-c.c. and 7·3 for the 500-c.c, mod el.

It will be not ed in t he tabl e of modifications tha t t he compression plate on the 500-c.c. model was discarded for the

1952 season. Therefore a new piston of the 1956 type must

be us ed to raise th e compression ratio on this model.

On similar models made before 1952 th e co mpress ion pl ate can be discarded, providing the ridge formed in the cylinder

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barrel at the end of piston-ring travel is also removed. Otherwise the top piston ring will break by contact with the ridge.

The 350-c.c. civilian models do not use a compression plate; therefor e a new piston to give t he above rat io is need ed. No alteration in ignition timing or carburetter is necessary after this alteration,

A special typ e of piston is us ed on Scrambles models to give a ratio of 9·5 for the 350-c.c. and 8·3 for the 500-c.c., these

ratios are not recommended for touring models.

For continued fast driving, a sparking-plug with a higher heat factor is beneficial, suc h as t h e K.L. G. FE . 10 0 or F E.220 for engines with alloy head or K.L.G. F.100 or F.220 for

engines wit h iron h ead s.

CARBURETTERS (1945 ONWARDS)

In view of the numerous types fitted since 1945, a ta ble of

types used, compiled from the carburetter makers' records are so that rectification as to whether the correct type of carburetter is in use.

350-c.c. MODELS

Year.

1946-50 I951-53 1954 1955

1956-57

Type.

76 DIJ 76 AE/IAK 76 AV/IED

376/5 376/5

Bore

size, in.

1 1 1 1 1/16

1 1/16

Slide.

6 x 4 6 x 4 6 x 4

376/060.3

376/060.3½

Needle

position.

2 2 2

central

Main

jet.

150 150 150

210 210

500-cc. MODELS

1946-53 1954

1955 1956-57

89 B/IAK 89 N/IED 389/1

389/1

1 5/32 1 5/32 1 5/32

29 x 4 29 x 4

389/060.3

389/060.3½

3 2

central

180 180 260 260

Erratic Running at Slow Speeds

If the engine fails to run slowly, or idle, this is usually

associated with the pilot jet. The trouble can also be due

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to distortion of the carburetter flange (see " Cleaning the

Carburetter ", Chapter I) .

On all carburetters fitted before 1954 a definite improvement in the slow running and control can be effected by making a slight alteration to the mixing chamber . Whilst this alteration is not difficult, the utmost caution must be exercised in

the manipulation of the very small drill that is used. The equip me nt needed is a No. 66 drill (0·033 in.), a watchmaker's han d chuck or Eclipse pin vice No . 121.

Remove the carburetter and dismantle it completely, ex-

cluding the slide stop screw. W ith the drill firmly secured in the vice introduce the drill into the hole drilled diagonally in the mixing chamber leading into the inlet tract (pilot outlet), see Fig. 20, from the counter-bored end. Rotate the drill slowly with the vice held between finger and thumb, without using force. Withdraw the drill from time to time to clear metal from the flutes in the drill and continue drilling until the end of the drill emerges into the inlet tract. Remove the burr caused by the drill breaking through. Deal with the

carburetter as previously recommended in " Decarbonising " (Chapter 1). It should now be possible to obtain full control over the pilot adjustment, as the volume of fuel (not the quality, affecting consumption) has been increased.

A.J.S. MOTOR CYCLES

If everything is in order the pilot control screw should be

1½ to 2 turns open from fully closed position. It is most important to adjust the pilot air-control screw to obtain positive slow running as quickly as possible before the engine becomes unduly hot. If made with the engine unduly hot, the setting will be weak under running conditions.

T he sparking-plug gap should be between 0·020 and 0·022

in. to ensure positive slow running. See " Technical Dat a "

for settings for carburetter.

He av y Petrol Consumption

Assuming the internal condition of the engine is normal and without loss of valve-spring pressure, the only part of the carburetter that can wear and affect consumption is the needle

jet. If ovality in the needle aperture occurs the fact of

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FIG. 20.—ARRANGEMENT OF CARBURETTER FITTED UP TO

AND INCLUDING 1954.

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A.J.S. MOTOR CYCLES

lowering the taper needle will have no beneficial effect in reducing consumption.

A new needle jet should be used in the first instance, before investigating further. A punctured float will also cause excessive petrol consumption.

Throttle Slide

The meaning of the type or marking on the throttle slide is not generally known. On 350-c.c. models the normal slide is type 6 x 4. The first figure is the carburetter type and the second is the amount of cut-away from the bottom edge of the slide measured in 1/16 in., which in this case is ¼ in. The slide cut-away has an influence on the depression of the fuel supply between the pilot and needle setting, thus affording a means of tuning at this position of the throttle range. Consequently, the use of a slide with a larger cut-away weakens the mixture between the two positions previously described. Conversely, a slide with a smaller cut-away richens the mixture.

It is not unusual for owners to use a throttle slide with a smaller cut-away to overcome a flat or weak place after leaving the pilot-jet position. This must necessarily increase petrol consumption, and the remedy is to ensure the pilot setting is not unduly weak before a change of throttle slide is made. Should the cut-away be unnecessarily small, a surging effect will take place at road speeds of about 30-40 m.p.h. Throttle slides can be obtained with a variation in cut-away of 1/32 in. to provide finer adjustment.

It is therefore imperative that the slow-running (pilot adjustment) is correctly set before any other alteration to carburetter settings is contemplated.

Checking Petrol Consumption

It is difficult to assess the amount of fuel consumed over a known mileage, as by reason of the irregular shape of the petrol-tank base it is not possible to run the machine until all the fuel is consumed.

For accurate recording, the use of a small test tank, say to hold 1 pint, is a satisfactory medium for this purpose. Mount

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ENGINE OVERHAUL

that tank in a convenient position and fill it with exactly 1 pint of fuel. Set the trip on the speedometer to " Zero " and drive the machine on " give and take " roads at 40 m.p.h. until the fuel is exhausted.

If, for example, the distance covered is 10 miles, then the fuel consumption is 80 m.p.g. If the slightest amount of fuel is spilt during filling, empty and refill so that exactly 1 pint is used for this test. This is essential if an accurate recording is to be made.

Locating the Taper Needle

The main jet size has been determined by the makers. No gain in fuel consumption will be achieved by reducing the main jet size, as this setting does not have any effect until the throttle is at least three-quarters open.

In consequence, tuning for a better fuel consumption is confined to the slide cut-away and needle position. The needle position affects performance and consumption only at road speeds round about the 50-m.p.h. mark. Raising the needle one notch at a time will improve acceleration. Generally speaking, fuel consumption is governed by the amount of throttle opening used.

Banging Noise in Silencer

This may be due to a weak pilot setting when the throttle is closed, or practically closed, or to a rich pilot setting with an air leak between the exhaust pipe and the port.

To rectify, reset the pilot as required and make the exhaust pipe a tight fit in the exhaust port by driving a taper wedge, shaped like a carrot, into the pipe at the port end to increase its diameter.

The Monobloc Carburetter

This carburetter was first introduced for the 1955 season, and incorporates such features as detachable pilot jet and a combined fuel and mixing chamber. The primary air choke has a compensating action, in conjunction with two bleed holes drilled in the needle jet, which serves the dual purpose of air—

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A.J.S. MOTOR CYCLES

FIG. 21.—THE MONOBLOC CARBURETTER FITTED FROM 1955.

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compensating the mixture from the needle je t a nd providing a well of fuel outside t he needle jet for snap acceleration.

T he s equence of tun ing is similar to t hat of th e earlier-type carburetters, and attention will be confined to cleaning o ut the float chamber, the filter or removing obstructed jets. The

assembl y details for Monobloc carburetters are s hown in Fig. 21.

Removing the float

Ta ke away th ree scr ews fixing the sid e cove r an d raise the

float off it s hinge p in. After cleaning the float chambe r, shake

the float; when held close to one ear it should be possible to

hear fuel washing inside the float if it is punctured. It is preferab le to replace the float instead of attempting to repair it.

When replacing the float ensure that the narrow hinge leg is uppermost.

Removing the Float Needle

Take away the banjo bol t, washer and filter gauze , unsc rew

the needle seating and lift out the needle. Clean the needle poi nt and also its seating. Han dle the needle and gauze with care , a s t he y a re fragile. Do n o t attempt to grind this needle.

Removing the Pilot Je t

Remove the pilot-jet cover nut with the washer. The jet can be unscrewed with a screwdriver, when it can be checked for obstruction. Check also the pilot by-pass and pilo t outlet.

When replacing the pilot jet do not use undue force in tightening, as this can deform the pilot-jet seat in the carburetter body and cause irreparable damage.

Jet-block Removal

Remove both air and throttle slides and the jet holder,

complete with needle jet an d main j et . Unscrew t h e throttleslide adjusting screw to its full extent. The jet block can then be lifted upwards from the mixing chamber. Upon

reassembly make sure the gasket at th e base of je t block is u n -

damaged, otherwise fuel will leak acros s its face, c aus ing rich mixture and heavy petrol consumption.

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When replacing the slider carefully locate the taper needle

into th e mi ddle hole i n t h e jet block.

Carburetter Adjustment

T he main je t size has been determined by the makers, and further adjustment is confined to the needle location or pilot setting. It is imperative to ensure correct pilot-jet adjustme nt before any further alteration is m ade . Fir st check those settings associated with positive slow running, i.e., plug gap, contact-breaker gap and valve-rocker adjustment.

Start by screwing home the pilot air-adjustment screw, then unscrew to one and a half turns. With machines fitted with manu al ignition control r etard the lever about 1/8 in.

Start the engine, open fully the air lever and run until the engine is warm. Set the throttle-adjusting screw, so that the engine runs too fast for an idling, or slow-running, speed with

twist-grip closed.

Slowly unscrew the throttle-adjusting screw to reduce

engine speed, when t he engine will hesitate or falter. Screw

in or out the pilot-adjusting screw until the engine runs evenly

and slowly. If the engine speed increases unduly the pilot setting is too weak for normal us e. In which case repeat the process, opening the throttle and closing sharply to establish tha t positive slow running occurs.

If the engine becomes unduly hot during this process a false setting will occur, as the slow running will cease when the machine is on the road and its temperature dec r e ases . Therefore, endeavour to set the slow running before the engine becomes unduly hot.

A.J.S. MOTOR CYCLES

Excessive Petrol Consumption

When it is known that t he internal condition of the engine is normal, first ascertain that intermittent flooding is not the cause. Also check that the pilot jet is correctly seated. Try the effect of a new nylon needle and check th e washer at the base of the jet block for deformation. If the machine has covered a considerable mileage replace th e needle and needle

jet. A smaller jet size is not advocated.

On 350-c.c. models made before 1956 using this type of

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ENGINE OVERHAUL 63

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FIG. 22.—SETTING TIMING GEARS ON

FIG 23.—VALVE-TIMING MARKINGS FOR

1945-48

1949-51 ENGINES.

MODELS.

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carburetter, try the effect of a slide with a larger cut-away (S i ze 3½), w h i c h s hould improve petrol" consumption by 9-13 m.p.g. at 40 m.p.h.

If at any time t he jet block is replaced, en sur e th at the holes drilled in the mixing chamber are in complete register with the holes for the primary choke.

As a final resort, lower the taper needle to the extent of one notch only. Lowering the needle position unduly will impair acceleration.

All types of cams as well as the timing pinion are marked during manufacture. Providing the timing-side shaft is correctly located, timing must be corrected if the maker's marks are used for assembling the cam gear.

As the method of cam marking has been altered since 1945 to avoid confusion, the year of manufacture a nd ty pe of mark-

ing used are described below.

1945-48.—Cams are marked with a dot. Th e pinion has a

line on the outside face midway in the keyway slot (see Fig. 22).

1949-51.—Cams are marked one and two for use on both Matchless and A.J.S. engines. Number one marks are for Matchless engines, number two for A.J.S. engines (see Fig.

23).

1952-53 (VALVE 1950-51 models, with the exception of assembling, when number two marks are used for both Matchless and A.J.S. models inlet and exhaust. (Both models now have magneto in front of cylinder.)

1954-55 (VALVE type (mark ed HL). Additiona l figure number three is used for setting inlet timing on the 350-c.c. model only. Number two

marks for the 350-c.c. exhaust and for both valves of the

500-c.c model (see Fig. 24).

1956-57 (VALVE

the 350-c.c. inlet, number two for th e 500-c.c. inlet and number

one for th e 350-c.c. and 500-c.c. exhaust (see Fig . 24).

Note.—The latest type camshafts do not use a keyed shaft

A.J.S. MOTOR CYCLES

VALVE TIMING

LIFT

0·326 in.).—Marking similar to

0·362 in.).—Cams are of t he high-lift

0·362 in.).—Number three used for

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FIG. 24.—VALVE-TIMING MARKINGS FOR 1954-55

to drive the magneto. If a keyway is not visible in the cam wheel use No. 1 mark for the exhaust-cam setting, before

1956-57.

Refitting Cams

The method of fitting the cams is the same for all marks.

Proceed as follows:

(1) Turn the engine until the mark on the pinion points

to th e left of inlet-cam-wheel b ush h ole.

(2) I nse rt the inlet cam with its mark in mesh wit h t he

mark on th e pinion.

(3 ) Tur n t h e engin e forward (about 20°) until the mark

on th e pinion now poin ts to th e exhaust-cam-wheel bush

hole.

(4) I ns ert the exhaust cam with i ts mark in mesh with

the mark on the pinion.

Do not neglect to apply oil to the camshafts before fitting.

Also generously oil all pinion teeth.

ENGINES.

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FIG. 25.—SERVICE TOOL KIT.

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Checking Valve Timing

There is no useful purpose in deviating from the maker's markings. It should be remembered that any alteration is confined to one tooth on either the cam or pinion, which

represents 18° on the engine stroke.

As quietening curves are used on touring and high-lift cams, a push-rod clearance of 0·016 in. is used for checking valve timing.

FITTING A LATER TYPE ENGINE

It often happens that owners have the opportunity to purchase an engine of more recent manufacture than the one originally fitted, and that some doubt exists as to whether engines will interchange.

Providing the earlier-type engine is of the O.H.V. type, a later-type engine should interchange, as the crankcase mou ntings are identical. Engines made before the mid-season of

1948 used t h e narr ow -t yp e crankcase, a n d it is a si mple ma t t e r

to alter the crankcase-to-the-frame distance pieces.

For the 1954 season the lower crankcase boss hole was increased from 5/16 to 3/8 in. i n diameter. In t h is case, the two

front frame holes must be enlarged accordingly if a crankcase of t his ty pe is to be used in an earlier frame.

To use a 1957-type engine in an earlier frame, the flywheel driving-side axle must be exchanged for an earlier type , as an engine shock absorber is not used on the 1957 models. For chain-line arrangement, the distance taken from the centre of the clutch-sprocket teeth to the crankcase centre line (crankca s e joint) is 4 1/ 16 in.

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CHAPTER III

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HIS chapter deals with maintenance and fault location. The gearboxes and clutch covered include the C.P. type

(1945-51), B.52 type, and the A.M.C. 1957-type gearbox.

Chain Adjustment

Front-chain adjustment is effected by moving the gearbox. It must be emphasised that when this chain is adjusted the gearbox must be pulled back until the chain is tight and then moved forward until correct adjustment is reached. This is to prevent the gearbox moving and thus tightening the chain after adjustment.

Tightening Front Chain

To tighten the front chain proceed as follows:

(1) Remove the chaincase inspection cap. (2) Slacken the top gearbox bolt on the right-hand

side.

(3) Unscrew the forward nut on the gearbox-adjusting bolt three or four turns. Tighten the rear nut until the chain is just tight; this can be felt by inserting the index

finger through the filler-cap orifice.

(4) Unscrew the rear nut three or four turns. Tighten the forward nut a trifle at a time, checking the chain tension after each movement of this nut until the chain

whip is 3/8 in. As chains do not stretch evenly, the tension

should be checked in more than one position,

(5) Retighten the rear nut on the chain adjuster.

(6) Retighten the top gearbox-bolt nut firmly. (7) Replace the inspection cap.

Rear-chain Adjustment (1950-54 Models)

Wheel alignment is checked at the factory by adjusting

the position of a small bolt screwed into the right-hand side

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of the swinging ar m; t he position of this bolt should not be altered.

Th e rear wheel is moved to adjust the rear chain fay turning the two cams, which move together, mounted on the rearwheel spindle.

The adjustment is carried out as follows:

(1) Wit h the machine on th e centre stand, slacken th e

nu t on th e right -han d side of the speedometer gearbox.

(2) Slacken the n ut s at the en ds of t he rear-w heel axle. (3) P u s h the whe el forward so b o th cams a re i n c on tact

with t he projections on t he swinging arm.

(4) Apply a spanner to the hexagonal body of the chain -side cam, t ur n the spanner until correc t adjustment is obtained (1 1 /8 in. wh ip in centre run of chain).

Rear-chain Adjustment (Detachable-wheel Models,

1955-57)

Slacken the wheel-spindle nut and the nut on the brake

dummy spindle.

Slacken th e two lock-nuts on the chain adjuster, the n screw in the chain adjuster an equal amount until the correct chain whip is obtained, namely 1 1/8 in., in th e cent re of th e bot tom chain run.

Dynamo-chain Adjustment

The dynamo armature shaft is eccentric to t he body of the

dynamo. By partially revolving the dynamo in its housing,

th e distanc e between t he two chain sprockets is varied to provide chain adjustment.

Tightening the Dynamo Chain

To tighten the dynamo chain:

(1) Remove the inspection cap from front chaincase. (2) Slacken the dynamo clamp bolt (located between

th e engine plates).

(3) Apply a spanner to the flats cast on the left-hand

side of the dynamo. Rotate the dynamo anti-clockwise

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A.J.S. MOTOR CYCL ES

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Rear-chain Lubrication

To lubricate the rear chain effectively, wit h a lasting effect, remove the chain and clean it in paraffin. Obtain a small quantity of anti-centrifuge grease (see " Li st of Recommended

Lubricants ", page 165). Slowly hea t th e gre ase in a fla t t in until it is fluid, immerse the chain, then reheat the grease, which will have cooled off when the chain was immersed, unt il the grease is again fluid.

Leave the chain to soak; wipe off the surplus grease, then refit the chain. After a few miles, the grease having been squeezed out of the links and rollers, it may be necessary to readjust the chain.

Th e time devoted to such process will be amply repaid, particularly during inclement weather, by prolonging the life of the chain.

GEARBOXES

Three types of gearboxes have been used on the singlecylinder models. Type C.P. was used for the 1945-51 seasons. T yp e B.52 fo r the 1952-5 6 an d t he A .M .C . gearbox for 1957. Prior to 1948, gearboxes are lubricated with light grease, After this year, engine oil is used for lubrication—normal

content, 1 pint.

The B.52 gearbox is a great improvement over the early

type, the foot-change operation is smooth, and can be im-

proved further if all the operating par ts used for gear selection are highly polished.

The CP . gearbox remained basically unaltered for several years, although it was superseded for 1952. This is no indication that it was unreliable or unsatisfactory.

GEARBOX FAULTS (CP. TYPE, 1945-51)

Gearbox Noise

A noisy third gear is usually associated with wear on the

layshaft fixed pinion and possibly the main driving gear which

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A.J.S. MOTOR CYCLES

FOR KEY TO LETTERS, SEE PAGE 73.

FIG. 26.—SECTIONAL VIE W O F TRANSMISSION SYSTEM—CP TYPE.

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KEY

FIG. 26.

Clutch assembly.

Main gear-wheel.

Mainshaft sliding gear.

Mainshaft third gear.

D. E.

Layshaft small gear.

Layshaft second gear.

Layshaft first gear.

Layshaft third gear. Final-drive sprocket.

Kick-starter crank.

Kick-starter axle.

Kick-starter quadrant.

Kick-starter ratchet pinion.

N. O.

Kick-starter ratchet driver. Kick-starter stop.

Clutch-operating lever.

Clutch thrust rod.

Gearbox mainshaft.

Layshaft.

Layshaft sliding dutch.

engages with the layshaft fixed pinion. Wear on the layshaft

bushes can also create a similar noise.

Top Gear Disengages Under Load

Check the striker forks for wear. If these are in order the main driving-gear bush may have moved towards the kickstarter side of the gearbox, preventing full-tooth engagement of the gears.

To remedy, replace the bush and ensure that it is a good fit in the main driving gear. Two bushes are used for the main-shaft in this gear. A weak gear-indexing mechanism will have a similar effect.

Faulty Gear Selection

If this is present with more than one gear check the footchange assembly, which is " timed ". Remove the footchange pedal and take away the nuts securing the kick-starter case cover. Remove the foot-change assembly. The small

pinion on the camshaft is marked with letter " O ". Using pliers, turn the shaft until letter " O " is at nine o'clock. Take

out the foot-change mechanism for examination when it will

be seen that the toothed sector which engages with the camshaft pinion and is also marked with a letter " O ". Fit the assembly with marks in register, then refit the kick-starter cover and the foot-change pedal. The gears should now be indexed correctly.

Should the trouble still prevail, take out the gears and

examine the strike forks for wear.

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Noisy Gear Engagement

This usually occurs when starting out, when first gear is engaged. Generally, th e fault is due to torqu e on th e gearbox mainshaft caused by clutch " dr ag ".

Th i s can be proved by holding out t he clutch, with th e lever against the handlebar, and then depressing the kick-starter crank several times. If, after this operation, th e gear engages without noise, clutch drag is the cause of the trouble. Clutch dra g can be due to :

(1) Excessive lost motion in the clutch-operating

mechanism.

(2) Gumminess of clutch friction plates, due to oil. (3) Buckled steel clutch-driven plates. (4) Clutch-spring pressure plate not runn ing tr ue.

To remedy (1) refer to clutch adjustment on page 89; (2) and (3) can be dealt with by disma ntling t he clutc h and washing all parts in paraffin. Put the steel plates together and hold up to t he light; distorted or buckled plates will be observed.

To chec k (4) re mo ve t h e o ute r p o r t ion o f the front ch a in c a se , pul l out the clutch lever on the handlebars, depress the kickstarter and observe if the pressure plate is running out of tr ut h. Balancing th e clutch-adjusting screws, within reasonable limits, should correct this fault.

Check also the rim of the pressur e plate for uneven machining, Insufficient clutch-plate separation, due to wear on th e operating mechanism, will also create clutch drag and noisy gear opera tion. Should th e clu tch suddenly fail to disengage, check the nut retaining the kick-starter ratchet pinion, and check th e thrust st ud in the clutch pressur e plate. If these are not at fault check the clutch-hub retaining nut.

Should this trouble develop gradually, check the push-rod ball for wear, together with the operating lever in the kickstarter case.

A.J.S. MOTOR CYCLES

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Kick-starter Fails to Turn Engine or Jams

Check the qua drant on the kick-start er crank for damage to

the first tooth. This tooth can be ground off to restore opera-

tion to normal, wi th slight loss of leverage.

A disintegrated stop rubber will have the same effect.

Kick-starter Fails to Operate

Remove the kick-starter cover and check the ratchet pinion and spring for security. T he pinion may be sluggish on the mainshaft if th e s pr in g is in order.

Side Movement, or Rock, on Clutch Sprocket

Th is may be due to wear on the clutch hub rollers or bearing sleeve. If the bearing surfaces are in order reduce the overall width of the beari ng sleeve o n the gearbox mainshaft and fit new rollers.

Use an anti-centrifuge grease to lubricate the rollers before

reassembly.

End-play on Gearbox Mainshaft

If the kick-starter-pinion retaining nut is tight the small bearing accommodating th e mainshaft in the kick-starter case may be worn. T h e use of shim washers between this bearing and its housing will absorb slight movement.

Broken Teeth on Gears

If a gear has to be replaced for this reason, have th e mainshaft and the layshaft checked between centres for bending before reassembling the gearbox.

These shafts can be straightened, between V-blocks, pro-

vided that the bow is within reasona bl e limits.

Clutch Rattle with Engin e Idling

Th is is due to backlash between th e tongues on the clutch friction plates and the slots for the clutch driver. Thi s can be proved by pulling back the clutch lev er on the handlebar, when the noise should cease.

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To remedy, the metal or tongues on the friction plates can be drawn out. Place the tongues of the friction plates on a flat vice or block of steel and tap the tongues lightly with a light hammer to draw out the metal; thus reducing the clearance between the tongues and the slots in the clutch driver.

GEARBOX FAULTS (B.52 TYPE)

As the clutch arrangement on this type of gearbox is basically the same as th e C P . type (excluding the withdrawal mechanism), refer to the instructions for this type-

Faulty Gear Selection

This is, invariably, due to t he small plunger which engages with depressions in the cam barrel sticking or sluggish in its housing. Cleaning the outside diameter of th e plunger with emery cloth is usually sufficient to restore the gear selection to normal. Check also the two steel pins in the selector shafts. Wear on these pins will cause bad indexing.

A.J.S. MOTOR CYCLES

Top Gear Disengages Under Load

T hi s is unco mmon, b ut i n some gearboxes th e housing for

the main bearing is machined too deeply. This causes only partial engagement between the main driving gear and the mainshaft sliding gear.

To create deeper dog engagement, a steel washer must be

made to fit over t he shaft between th e main d riving gear and

the main bearing. The washer should be approximately 1/16 in . thick.

Evid enc e of shallow dog engagement can be s een on the two

pinions concerned.

Gears Disengage Under Load

This fault is usually due to a weak V-shaped foot-change centralising spring mounted in the kick-starter case; stretch th is spr ing slightly to increase pressu re.

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FIG. 27.—FOOT-CHANGE SPRINGS.

A weak foot-change quadrant coil spring will display the

same symptoms. These springs are shown in Fig. 27.

Noisy Gear Selection

When a grating noise ensues as the first gear is engaged, check the clutch-withdrawal mechanism. To fully understand the working of t he clutch-operating mechanism, a study of the arrangement shown in Fig. 28 should be made.

From this, it will be seen that any reduction in leverage brought about by shorte ning the clutch cable (unscrewing t he cable adjuster) will reduce the movement of the clutch push rod. This usually creates a clicking noise when the handlebar lever is operated.

To remedy, r u n down t he clutch-cable adjust er as far as it will go. Next, t ur n to the opposite side of th e gearbox. R emove the chaincase outer portion or clutch cover, whichever is fitted. With a sparking-plug box key, release the nut locking the thrust cap or stud, mounted in the centre of the clutch-spring pressure plate. Place a screwdriver in the thrust-stud slot, screw in the stud exactly half a turn and

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FIG. 28.—CLUTCH-OPERATING MECHANISM—B.52 TYPE.

A.J.S. MOTOR CYCLES

Fixed actuating plate.

Operating lever. Mainshaft.

C. D.

Clutch sprocket.

Clutch spring.

Lock-nut for thrust cup.

Thrust cap (in pressure plate).

retighten th e lock-nut, taking care that the stud does not move

during this process.

Now, go back to the clutch-cable adjuster, and unscrew un t il

there is 1/8-3/16 in. free movement in the oute r casing for the

clutch cable. Retighten the cable-adjuster lock-nut

Should the trouble still prevail, check for " clutch drag "

as described for t he C.P.-type gearbox (see page 89).

Clutch Rattle

Th e details given for the C.P . type clutch are applicable also

to this clutch.

Foot-change Lever Sticks

Th e most likely cause of this defect is friction between the foot-change shaft and its bearing in th e kick-st arter -cas e cover. First tr y the effect of squirting a little paraffin, or penetrating

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oil, around the shaft, and lean the machine over to the left to assist oil penetration.

If this does not effect a cure take off the kick-startercase cover, ease down the shaft with emery cloth, oil and refit.

It should be noted that a weak centralising s pring can have the same effect.

Kick-starter Crank Sticks after Use

Release the screws fixing the kick-starter-case cover; operate the kick-starter crank. If the crank does not return to its normal position the return spring is probably broken, see " Dismantling Gearbox " (page 86).

If the kick-starter returns, with the cover screws loose, it is quite possible that the kick-starter axle bearings, in the case and the cover- are not in line, due to movement of th e cover.

To correct, lightly tighten the cover-fixing screws, then with a mallet tap the cover upwards from underneath. Retig hten th e cover-fixing screws firm ly, bu t do not ove rtig hten ; the crank should then operate normally.

A formation of rust on the kick-starter axle will have the same effect.

Note that it is dangerous to drive with the kick-starter trailing or with the quadrant in engagement with the ratchet pinion. T he ratchet pinion will seize on th e mainshaft if t h e machine is used in th is condition for any length of time.

Oil Leakage from Gearbox, Driving Side

The Super oil seal fitted to the gearbox shell will be satisfactory until t he machine has covered a considerable mileage. To determine where the oil leakage takes place, wash the gear-box shell with petrol and check that the oil level is correct by draining and refilling with exactly 1 pint of oil (SAE 50). Make a short road test, stop the machine and check the gear-box shell exterior for the position of the oil leakage.

This can take place from the two metal plugs sealing the

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shaft holes or from th e main bearing. Should the leaks com e from the two metal plugs, wash again with petrol and apply

jointing compound copiously around the plugs. Leave the

machine stationary until the jointing compound has " set ".

In the case of leakage from the main bearing, the oil seal

must be replaced.

Oil Leakage from Kick-starter-case Cover

This is usually due to a broken or deformed gasket, fitted between the case and cover. A new gasket fitted to the case with jointing compound will have the desired effect.

DISMANTLING AND REASSEMBLING THE CP.

TYPE GEARBOX IN THE FRAME

A s t out box key or ring s p a n n e r is req u i r e d for t h e large n ut secu ring the gearbox sprocket a nd the n ut s ecuring t he clut ch

hu b t o th e mainshaft. Th e se n ut s are 2 1 /1 6 in. and 1 5 /1 6 in.

across the flats respectively. New gaskets for the kick-starter case and cover and a new oil seal for the main driving gear will be required.

A.J.S. MOTOR CYCLES

Removing Exhaust Pipe, Silencer and Chaincase

Remove together the exhaust pipe and silencer in one piece. Do not unduly rock the exhaust pipe sideways in the port, apply a little paraffin if difficult to ex trac t. Remove th e nut on the left-hand side footrest rod and also, on machines where the footrest is inside the frame, t he nut for the centre stand spindle, together with the lower front-frame uniting bolt. The footrest can now be moved forward.

Place a tray to catch oil when the outer po r ti on of the chain-

case is taken away, with the rubber band, if fitted, between the chaincase halves. Fully open the throttle, turn the engine against compression. Using a suitable ring spanner on the engine-shock-absorber fixing nut, apply a series of light blows on the end of the spanner with a light hammer, in preference

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to a levering motion, when the nut will release. Disconnect front chain. Tak e away the clutch-adjusting screws, spri ngs, cups and pressure plate. Turn back the tab-washer behind clutch-hub fixing nut.

Removing Clutch Assembly

Engage top gear, press hard on the rear-brake pedal and unscrew the hub nut. Place one hand on the back of the clut ch assembly and the othe r against the washer covering t he clut ch roll ers. Th en , t he complete a ssembly will come away without losing the rollers (twenty-four in num ber). Remove the long hexagon bolt uniting the rear chainguard to the back portion of the chaincase. After turning back the tab-washer unscrew three bolts (5/16 in. A/F) retaining the chaincase to the crankcase, and also the nut on the bolt in the centre of the case, which can now be removed.

Dismantling

Work on the gearbox can now commence by removing the drai n plu g in the bottom of th e gearbox shell and catching the oil drained in a suitable receptacle.

Remove:

(1) The clutch cable. (2) The four nuts fixing kick-starter-case cover and

withdraw, leaving the kick-starter crank and-foot-change

pedal in position. Fit a rubber band between the kickstarter crank and foot-change pedal to prevent the kickstarter spring unwinding.

(3) T h e clutch lever in the kick-starter-case cover, also the short push rod. Watch for the ¼ in. steel ball used between the short and long push rods.

(4) T h e kick-starter pinion nut ; pull off the pinion and

spring.

(5) The four nuts fixing the kick-starter case to the

gearbox shell.

(6) Th e kick-starter case. Watch for the twelve rollers

on the camshaft.

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(7) Th e slotted bolt at bottom of the gearbox shell, wit h

its spring, which operates the pawl.

(8) The whole of the gears and layshaft, except the main driving gear, with camshafts.

(9) T he rear chain. The mainshaft can now be with-

drawn from the clutch end of the gearbox. Using a chain ba r, which is simple to make (Fig. 29), with a short leng th of 5/8 in. x 3/8 in. chain attached, dr ape the chain

round the sprocket, with the bar propped against the

frame. Should it be inconvenient to make a tool of t his

kind, leave the chain attached and apply pressure on the

bra ke pedal to release the sprocket-fixing nut after turning

up the tab-washer. T hi s nu t is usually very tight, which is intentional, and for this reason the use of a chain bar is desirable.

(10) The sprocket spacing collars; recording the posi-

tion in which they are fitted.

(11) T he main driving gear; which can be tapped into

the gearbox shell.

(12) The main bearing; after extracting the circlip,

washer and oil seal.

(13) The mainshaft ball bea ring in t he kick-sta rte r case,

which is also retained by a circlip.

A.J.S. MOTOR CYCLES

FIG. 29.—CHAIN BAR.

The gearbox is now completely dismantled, with the exception of the layshaft bushes. These bushes, a force fit in both the gearbox shell and kick-starter case, are made from self-lubricating bronze a nd a re s ome what brittle, so car e should be taken when new bushes which do not require reaming for size are fitted.

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FIG. 30.—CAMSHAFT ASSEMBLY.

Camshaft,

Pegs for forks.

Mainshaft fork

Extracting Bushes

To extract the layshaft bush in the gearbox shell, tap out the steel " glu t " or disc, th e n the bus h can be pressed into th e interior "of the gearbox shell. The bush in the kick-starter case can be pushed out by supporting the case with tub ing or a box key of suitable size.

There is very little load, or turning movement, on the camshaft bus h in t h e gearbox s hell. To remove, use the method described for extracting the layshaft in the shell. Details of th e camshaft ass emb ly a r e s ho wn i n F i g . 30 .

Two inexpensive self-lubricating bushes are fitted in the main gear p inion. Ins ert t he mainshaft and check for wear. These bushes are a force fit and can be pressed out without difficulty. They must be a tight fit in the pinion, for a loose

bush will affect top-gear engagement. The pinion on the layshaft which engages with the main gear should also be a

tig ht fit on the splin es for th e layshaft. If th e shaft is chip ped ,

or a pinion loose, fit replacements. Carefully examine the

stri k er forks on the camshaft for wear, as a b adly worn fork can allow two gears to engage simultaneously, with disastrous results.

Layshaft fork.

Pinion

Locking-pawl groove.

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Reassembling Gearbox

Wash and oil all parts before reassembly. Replace in the following order:

(1) The main driving bearing, oil seal, retaining

washers and circlip.

(2) The main gear, with spacing collars, washers, chain sprocket and tab washer, with fixing nut. Apply chain bar firmly, tighten the sprocket nut and turn down the tab-washer.

(3) The mainshaft; through main gear.

(4) The gears on the layshaft in the order shown in Fig. 31. The fixed p i nion is fi tte d t o the short end of the

layshaft.

(5) H old th e layshaft assembly in han d, w ith the fixed

pinion on the left. Take up the camshaft (small pinion

to the ri ght), and engage the larger of the two stri ker forks in t h e groove for the sliding clu tch .

(6) Hold the mainshaft sliding gear, large pinion to the left, along the camshaft assembly, so that the smaller strik er fork engages with its central groove.

(7) Insert the entire assembly into the gearbox shell, sliding the mainshaft gear along the mainshaft, and push home, locating the camshaft and layshaft in to th e res pec tive bushes.

(8) Slide the remaining free pinion on the mainshaft.

(9) Pawl, s pri ng and slotted screw, locating gears.

(10) The twelve rollers, with grease to hold in position.

(11) The mainshaft ball bearing for kick-starter case; locate with circlip.

(12) Paper washer for gearbox shell, with grease

applied on gearbox face.

(13) The kick-starter case. Ensure that the rollers enter the housing in the kick-starter case. Fit the four case nuts and firmly tighten.

(14) The ratchet pinion bush and spring on mainshaft ratchet pinion (teeth outwards). Follow with the ratchet driver and fully tighten the fixing nut.

A.J.S. MOTOR CYCLES

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(15) T he paper washer for the kick starter case, with

grease on face of case, carefully passing the washer over

studs to avoid damage.

Replacing Foot-change Assembly

Particular care is needed for this operation to ensure tha t the gears are correctly indexed. The small pinion on the camshaft is marked with a letter " O ". The sector engaging with the pinion is marked likewise. Proceed as follows:

(1) Tu rn the camshaft til! the " O " is at nine o'clock. (2) Fit the sector, with the " O " stamped on it, to

mesh wit h " O " on the small pinion.

(3) Appl y g raphi te grease on th e lengt h, an d bot h ends of the long push rod a nd inser t it into the mainshaft from the clutch end with 2 in. protruding.

(4) From the kick-starter end of the mainshaft insert the ¼ in. steel ball, short push rod, with the slot nearly vertical.

(5) Take u p the sprin g box. See tha t the springs are not broken and that the four small steel plates are in position.

(6) Place the metal cover on the sp ring box and fit the quadrant with its peg engaged between the two small springs.

(7) F it the rocking pawl. T he complete assembly can now be inserted in the kick-starter case, locating the peg in case between the two large springs.

(8) Place the gasket in position. Put back the case cover, after discarding the rubber band, holding the kickstarter crank in its normal position, then push the cover firmly home. If the cover does not go fully home this may be due to the rocking pawl being out of position (work the gear pedal up and down) or the slot in the short push rod engaging with the clutch-operating lever.

(9} Fi t th e gear-change indicator and th e clutch ca ble.

(10) Fi l l th e gearb ox w i t h 1 pi n t o f engi ne oil S A E 50 .

(11) Reasse mble t h e c lu tch in t h e rev ers e or de r.

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DISMANTLING AND REASSEMBLING THE

B.52 TYPE GEARBOX IN THE FRAME

Th e general arrangement shown in Fig. 31 illustrates the internal gearbox lay-out, together with the foot-change mechanism and the kick-starter.

Removing the Kick-starter-case Cover

To inspect the gear-change, clutch-operating mechanism

and kick-starter remove the kick-starter-case cover as follows:

(1) Drai n t he gearbox after removing the drain plug in

th e bo tto m of th e gearcase.

(2) Unscrew the filler cap on the kick-starter-case

cover.

(3) Screw down the clutch-cable adjuster, to permit the

clutch-cable wire to be disconnected.

(4) Unscrew the clutch-cable adjuster to remove the

cable.

(5) Remove the nut securing the gear-position disc,

with its spring.

(6) Take out the five cheese-headed screws securing

the case cover.

(7) Pull off the case cover about ½ in., turn the kick-

starter crank so that it can be tied to the foot-change lever

with a rubber band, preventing the kick-starter from

unwinding.

(8) Th e case cover can now be taken off.

A.J.S. MOTOR CYCLES

Parts subject to wear are the plunger, or thrust dowel, the steel ball and the clutch push rod. Wear of this kind is caused by continual pressure on these two parts, see " Clutch-cable

Adj ustm ent " (p age 89).

Refitting the Kick-starter-case Cover

After refitting the parts in the reverse order to that given above ensure that the fixing screws are correctly positioned

as detailed.

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FIG. 31.—SECTION THROUGH GEARBOX SHOWING GEARS AND

CLUTCH WITH ACTUATING MECHANISM.

Low gear on mainshaft.

A. B.

Third gear on mainshaft.

Second gear on mainshaft.

Main driving gear.

Lo w ge ar on layshaft.

Third gear on layshaft.

Second gear on layshaft.

Small pinion on layshaft.

Fill w ith 1 pint of engine oil SAE 50.

Top screw 3 1/8 in. under head. Bott om s c r ew 2 7/ 8 i n. under he ad. Re ar s crew 7/8 i n, under he ad. Front scre ws 1 3/8 in, under head.

Removing the Gears

Remove th e kick-starter case as previously described. Re move the split pin securing the striker-shaft pins and withdraw both pins, cam barrel, spring and the short plunger, which engages with the cam barrel. Unscrew the mainshaft nut. Take off the kick-starter ratchet, ratchet-driver bush and spring. Upon removing the three screws in the kick-starter case , the case, complete with the cluster of gears in situ, will be

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exposed when the case is pulled away. If th e mainshaft has to be remo ved, release t he nu t on th e clut ch e nd.

Removing the Main Driving Gear and Bearing

The n ut securing the rear-chain sprocket is firmly tightened, therefore some difficulty may exist in holding the sprocket during this process. The chain bar (Fig, 29) is the tool for this j ob , fitted on to the sprocket, with the bar propped against the frame after disconnecting the rear chain.

Proceed by turning down the lock-washer behind the sprocket nut. Remove the sprocket nut, lock-washer, two distance pieces and then the sprocket, which can be pulled off easily without an extractor. Take away the distance piece, the circlip and the oil seal, when the main gear can be tapped into th e gearbox shell.

When the case is removed the two striker shafts and layshaft, with gear pinions assembled, will come away in a cluster. T he position of gears should be carefully noted.

A.J.S. MOTOR CYCLES

Refitting the Gears

With the mainshaft in the gearbox, fit the parts in the

following order:

(a) Tak e up t he layshaft and fit over splined end. (b) F it second-gear pinion, 24 teeth, a nd layshaft fixed

pinion, 18 teeth.

stri ker forks.

(d) Fit mainshaft third gear, 25 teeth, into layshaft

striker forks.

(e) Fit third gea r o n l a y s h a f t , 21 teeth. (f) Fi t low gear on mainshaft, 17 teeth, with spigot end

towards kick-starter.

(g) Fit low gear on layshaft, 29 teeth.

Wi th striker fork shafts mounted in the case, the complete

assembly can go into the gearbox shell. Reassemble the clutch and foot-change assembly.

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CLUTCHES

Clutch Operation (C.P. Type)

When the handlebar control lever is operated the clutch

lever A (Fig. 32) is moved in the direction of the arrow, thus separating the clutch friction plates. This action compresses the clutch springs, which must be evenly adjusted, otherwise clutch drag or slip will take place.

It will be observed tha t if wear takes place on the ope rating lever A, the short push rod B or the push rod D, the withdrawal movement of the clutch will be curtailed by contact between the slotted end of the short push rod B and the end of the main- shaft.

To increase the movement, turn the sleeve nut clockwise (usually half to one turn will suffice). Replace the cap and check the movement of the lever with a finger inserted in the oil-filler plug orifice, To decrease the movement, rotate the sleeve nut anti-clockwise.

Removing the Clutch Cable

To remove t he clutch cable proceed as follows:

(a) R emove t h e oil-filler p lu g . (b) Screw home th e clutch-cable adjuster. (c) Press in the lever with a screwdriver to disengage

the clutch-cable inner wire.

(d) Uns crew th e clutch-cable adjuster completely. (e) Disconnect t he inner wire from the handl ebar lever. (f) If numerous cable clips or insulating t ape are used

to secure the outer cable to the frame tube it may be necessary to remove the petrol ta n k.

Replacing the Clutch Cable

Reverse the removal procedure. Take care to ensure that

sharp bends do not occu r in th is cable.

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Lubricating the Clutch Cable

The benefit of a well-lubricated clutch cable has to be experienced to be appreciated. With th e cable removed, shape a small funnel m ade from pla sti cin e m ou l de d on t he e nd of th e outer cable. Hold the cable vertical and fill th e funnel with

A.J.S. MOTOR CYCLES

FIG. 32.—CLUTCH-OPERATING MECHANISM—CP TYPE.

A. Operating lever.

B, C, D. Push rods and bearing.

paraffin to assis t oil pen et ra t io n; wh en th e paraffin has drai ned down the cable fill the funnel with light oil. Suspend the cable to allow the oil to p ercolate down th e inner w ire.

Clutch Slip

This can be result of:

(a) Insufficient clearance (correct clearance should be

1/32 in.) between the clutch lever, 175-X-4, and the

plunger, 330-X.

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(b) Insufficient free movement (correct amount is

1/8-3/1 6 in.) of clutch handlebar-operating lever b e fore re-

sistan ce of the clutch springs is felt.

fouling the oil-filter plug.

If the above p oi nt s ar e no t at fault, t he n t he re may be oil on

the clutch-plate friction discs, or the clutch springs may be

we ak (normal fr e e length 1 ¾ in.).

Should the fault be due to oil-impregnated friction inserts, the effect of washing all the friction plates in petrol and then dus t in g them co p i o us l y with Fuller's e ar th s hould be tried. I f

it proves ineffective, replace the inserts with a ty pe , now available, which is impervious to oil. If clutch slip has prevailed

for any length of time the heat generated will probably have

weakened the clutch springs. In this case, to avoid subsequent attention , fit a new s et

Note t hat o n the C P . type gearboxes a large n ut was used

to retain the clutch hub on the mainshaft, and it is possible

for the clutch spring cups to foul this nut and cause clutch slip.

To correct, use the slightly smaller B.52 type clutch hub

nut.

Dismantling and Reassembling the Clutch Complete

Remove the following:

(1) T h e outer portion of chaincase. (2 ) T he five scr ew s f or t h e c l ut c h, w i th p re s su r e p l at e ,

springs and cups.

(3) The lock-washer under the clutch hub nut.

(4) Engage top gear, fit a box key to the clutch hub, press on rear-brake pedal and unscrew nut. Disconnect the front chain.

(5) As t h e clutch hu b is on splines, a tool is not needed to remove it. Tak e away the clutch assembly complete, bu t wat ch for t he clu tch rollers (24), which will dro p ou t when the assembly is removed.

(6) The gearbox mainshaft.

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FIG. 33.—ARRANGEMENT OF CLUTCH-OPERATING LEVER.

Clutch-operating lever. Screw, fixing cap to kick-

starter case cover.

Ca p , cov erin g sleeve (screwed

to kick-starter case cover).

Sleeve, or nut, for operating

lever fork.

A.J.S. MOTOR CYCLES

Fork, for operating lever. Pin, or axle, for operating

lever.

Operating plunger-

Ball bearing for operating

plunger.

To reassemble, use anti-centrifuge grease to stick rollers in

position. Reverse the dismantling order.

1957 TYPE GEARBOX (A.M.C. TYPE)

This gearbox is entirely new in design, wit h a shock absorber incorporated in the clutch assembly. It will not interchange with earlier types unless special rear en gine plates are made to adjust the chain line. Engine oil SAE 50 is use d to lubricate th e gearbox—normal content 1 pint.

Foot-change Operation

If there is difficulty in selecting the gears, first check the pawl-operating spring (Fig. 34). If this spring is incorrectly fitted or distorted,' gear selection will not be positive. It is

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vital that the straight leg of this spring is in the uppermost position as shown.

Where the s pring is correctly fitted, t ry th e effect of fitting

a new spri ng. A new-type plunger spring will eliminate stiffness in gear operation. Polishing the periphery of the cam plate is also beneficial. Cl utch drag will also cause noise and difficulty in selecting the gears.

Clutch Adjustment

The clutch-operating mechanism is shown in Fig. 35. This

should be studied if clutch adjustment is necessary.

To prevent pre-loading the operating mechanism in order to provide sufficient lost motion in the cable and push rod, 1/8-3/16 in. movement in the clutch-operating cabl e is essential. The movement can be checked by lifting the clutch outer casing near the adjuster or at the handlebar operating lever. To obtain this movement, first run down the clutch-cable adjuster as far as it will go. Tak e off the dome covering th e clutch assembly, unscrew the central lock-nut ( B, F ig . 35) for

FIG. 34.—PAWL-OPERATING SPRING ON A.M.C.

TYPE

GEARBOX.

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A.J.S. MOTOR CYCLES

FIG. 35.—CLUTCH, GEARBOX MAINSHAFT AND CLUTCH-

the thrust stud one or two complete t urns, using the sparkingplug box key.

Screw in gently the adjusting screw C till it is in contact

with the push rod. Unscrew t he adjusting screw exactly half

a tu rn an d retighten the lock-nut. It is advisable to keep the screwdriver in th e slot for the adjusting screw whilst tighten-

ing the lock-nut, to prevent the adjuster from turning.

Revert to the clutch cable and unscrew the cable adjuster

to give the required amount of movement, tighten the lock-

nu t and refit the clutch dome.

Clutch Slip

After considerable use and if the clutch' is slipped unduly wear on t he friction in serts will t end t o absorb t he lost motion or free movement in the operating mechanism and cause the clutch to slip. Reset the cable movement as described.

Where the correct cable movement is made, if clutch slip persists, first try the effect of increasing the clutch-spring pressure, by screwin g inwa rds, in turn, the thr ee c lutc h-spring

OPERATING MECHANISM.

A.. Pawl-op crating spring. B. Lock-nut. C. Adjusting screw.

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adjusting screws one complete turn. If clutch slip still prevails, dismantle the clutch. Oil on the friction inserts can be neutralised by copiously dusting the inserts with Fuller's earth.

Before re a ss em bl i ng examine the cup s, for the clutch s pring, for marking or evidence of contact with holes in the shockabsorber plate, Fig. 36. Where contact is shown, ease down the o utside diameter of each spring cup and pu t a chamfer or radius on the edge of each hole in the shock-absorber plate. Check t he free leng th of th e clutch spr ings, which is normally

FIG. 36.—CLUTCH SHOCK-

ABSORBER PLATE SHOW ING HOLES FOB LOCATION OF SPRING CAPS.

1 7/8 in. , and replace if the springs have collapsed or shortened to the extent of 3/16 in.

The correct position of the clutch-adjusting screws should

be with the s cr e w h ead just flush with the spring cup.

Dismantling Clutch Assembly

If th e gearbox is to be completely dismantled or the main-

shaft removed, the clutch assembly must be dismantled.

With the chaincase cover off, unscrew the three clutch-

spring adjusters.

Take off the pressure plate, the spring cups and spring. Engage to p gear, press hard on the brake pedal and unscrew the mainshaft n ut. The clutch centre, which is splined, should come away easily.

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Removing the Gearbox Outer Cover

Remove the oil-drain plug situated at the bottom of the gearbox shell, close to the dome nut for the cam plunger. Take off the filler-cap cover and disconnect the clutch inner cable from A, Fi g. 35.

Unscrew the bolt retaining the gear-indicator plate and leave the pedal in position. Take off the kick-starter crank and remove the five cheese-headed screws securing t he cover.

Gentl y ease off th e cover, by pulling on the gear pedal with care to avoid damage to the gasket.

Removing Gearbox Inner Cover

Remove the ratchet plate and spindle, also the clutchoperating arm and rollers. Unscrew the lock-ring securing the clutch-operating body and the ½-in. ball inside. Unscrew the mainshaft nu t, now visible after the clutch-operating body is removed.

Ta ke off the seven nuts fixing t he in ner cover to th e gearbox shell by gently tapping the rear of the cover until it is clear of the dowels, without damage to t h e gasket.

A.J.S. MOTOR CYCLES

Removing the Cam Plate

Remove the hexagonal dome nut on the front end of the gearbox shell and take out the plunger and spring. Also remove the two bolts above the plunger housing, when the cam plate and the quadrant can be taken off the gearbox shell.

Removing the Gearbox Internals

Remo ve th e low gear on th e layshaft, U nscr ew th e st rik er-

fork spi ndl e with a spanner placed on the two flats.

Dise ngage t h e strik er forks from th e c am plate a nd pul l out th e mainshaft complete with g ear s; also th e push rod. Take out the layshaft and gears, by rocking the shaft up and down un til it is clear of the halt-race.

Remove the lock-screw and plate securing the rear-chain

spr oc ket nu t . T h e chain bar s hown i n Fi g. 29 can be used t o

hold the sprocket whilst the fixing nut is unscrewed; this has

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a left-hand thread. The sprocket with the distance collar mounted on spline will come away without difficulty.

Gently tap the main or sleeve gear into the gearbox shell

and remove.

Removing the Oil Seal and Ball-races

The sleeve-gear oil seal is a close fit in the shell, and it is doubtful if it can be extracted without damage. Gentle heat applied t o th e gearbox shell will enable it t o come out easier.

Pre-heat the gearbox shell and drop it gently face down-

wards on a clean wood bench , th e races will then fall out .

Removing and Replacing the Clutch Shock Absorbers

Six rubber blocks (three thin and three thick) are incorporated in t he clutch hub, which are retained by a steel plate and three countersunk screws, see Fig. 36. To remove and replace these rubbers, this is best carried out with t he gearbox in the frame, unless an old gearbox mainshaft is available. Th is can be fixed in a vice to hold the clutch body whilst the rubbers are compressed. With the gearbox in situ dismantle th e c lutch to expose the shock-absorber assembly, Fig. 36.

Remove the three countersunk screws and tap round the cover plate as illustrated. The plate can then be prised out. Wit h the aid of a C-shaped spanner to engage in th e slots for the clutch plates or preferably a tool as shown in Fig. 8, engage top gear, press on the brake pedal and by lifting the

tool used to compress the thick rubbers, the thin ones can be

extracted with a short piece o f wheel spoke. T he thick rub -

be r s will com e o u t w i th o u t difficulty. Re vers e t h i s m e t ho d to replace the parts removed.

Clutch Bearing

Remove the clutch hub from the mainshaft and also the

three clutch spring stud nuts. Separate the hub from the back-plate and take out the bearing.

Reassemble in the reverse order.

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A.J.S. MOTOR CYCLES

A.M.C. OF

TYPE GEARBOX.

37.—ARRANGEMENT FIG.

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Kick-starter Assembly

With the gearbox outer and inner cover removed, use a piece of stiff wi r e shaped like a bu t t o n hook to p ul l ou t t h e e n d of the kick-starter return spring from its anchorage in its

housing.

Lift out, also, the opposite en d of the sp ring from the kic kstarter axle and withdraw the axle, which will give access to the kick-starter pawl with its plunger and spring. If the spring is inclined to slip out of its anchorage the turned-in end of the spring has taken a " set " and a new spring should be used.

Reassembling the Gearbox

If the gearbox is completely dismantled, apply gentle heat

to the gearbox shell. Fit the main bearing, layshaft bearing

and oil the seal with the spring inside. Pass the sleeve

gear through the bearing, fit the distance piece, sprocket and firmly tighten the sprocket nut , which has a left-hand thread.

Take up the mainshaft and fit on it the third- and second-

gear pinion with the striker fork in the third gear. Introduce

th e sp igot on th e stri ker forks int o t he groove in th e cam p late.

Take up t he layshaft and fit the small gear, thi rd and second gears on the shaft, with the striker fork in the second gear. Engage the striker-fork spigot into th e groove in the cam plate. After li ning u p the spin dle hol es in t he str iker fork, i nse rt th e spindle and firmly tighten. It will help to align the spindle holes if the cam plate is moved during this process. Finally, fit the kick-starter or low-gear pinion.

Refitting the Cam Plate

Position th e quadra nt and secure with the bo lt and washer.

Raise the lever on the quadrant into the top-gear position, with the radius on the lever in line with the top right-hand cover st ud .

Fit the cam plate, so that the first two teeth on the quadrant are visible through the groove in the cam plate, secure the plate with its washer and nut. Refit the cam-plate plunger, spring and dome nu t. Replace t he drain plu g.

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A.J.S. MOTOR CYCLES

Refitting the Outer Cover

With the kick-starter assembled, fit a new gasket if the original is damaged, fit the cover and firmly tighten the seven fixing nuts. Fit the mainshaft nut, clutc

h-operating body and

the steel ball.

Locate the operating body so that the actuating lever lines up with the hole in the cover for the clutch cable. Secure the lock-ring, fit the actuating lever and roller. Insert the ratchet plate and spindle.

See that the gasket is undamaged before fitting. Check the pawl spring for position (Fig. 34), with the straight leg in the uppermost position.

Fit the cover and secure with five cheese-headed screws. Assemble the remainder of parts removed in the reverse order described for dismantling.

Refitting the Clutch Assembly

Insert the push rod in the mainshaft. Fit the clutch hub on to the mainshaft, a spring washer and shaft nut, which must be very firmly tightened. If the back of the clutch hub fouls the sleeve bearing when the nut is tightened the hub splines are worn or damaged and should be replaced.

Proceed by assembling the clutch sprocket, steel and friction plates alternately, then the pressure plate, engaging the push rod into the screwed adjuster stud. Assemble the clutch springs, cups and adjusting screws with the head of each screw flush with the spring cup. Adjust the clutch cable as described elsewhere.

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Ajs 1948 1957 AJS Singles 5th Edition F Neill Ajs 1948 1957 AJS Singles 5th Edition F Neill

Specifications and Main Features

Frequently Asked Questions

User Manual