A.J.S. 3.46 H.P. User manual

A.J.S.Model33/7.
HANDBOOK
for
OVERHEADCAMSHAFT
TROPHYMODELS3.46H.P. 4.95H.P.
MANUFACTUREDBY
PLUMSTEAD,LONDON,S.E.18.
PRICE- ONESHILLING.
www.ajs-matchless.info

www.ajs-matchless.info

FOREWORD
In giving the following information we have endeavoured to
meet the needs of all A.J.S. Camshaft Model Owners—that is,
both the original A.J.S. Camshaft machines and the present Trophy
Models. Apart from detail modifications and improvements the
machines are very similar so that this booklet will apply to both
types of machines. On the assumption that the purchasers of
A.J.S. Camshaft Models are already conversant with the driving
of a Motor Cycle we have only included just covering remarks on
this subject. That accessibility has been very carefully studied
in designing A.J.S. machines will become apparent to owners
of Camshaft Models, when making adjustments of any descrip-
tion, so that no difficulties should be experienced in carrying out
the instructions contained in this booklet.
A.J.S.
Motor Cycles
O.H.C. TROPHY MODELS
3.46 H.P. and 4.95 H.P.
www.ajs-matchless.info

CONTENTS
PAGE
Foreword 1
Driving Instruction 3
Camshaft Engine Details 4
Dismantling and Assembling :—Engine 4, 7, 8 and 9
Engine Lubrication 9 an d 10
Dismantling and Assembling :—Gearbox 11 and 12
Clutch and Transmission 12, 13 and 14
Front Chain Cover 13
Carburettor 14, 15 and 16
Lucas Magdyno and Magneto 16 and 17
Ignition Timing 18 and 19
Rear Wheel Removal and Adjustment 19 and 20
Front
„ „ ,, ,, 20
Wheel Bearing Adjustment 20
Front Fork Adjustment 20
Steering Head and Handlebars 21
Gear Ratios .. .. .. .. .. .. .. .. 22
Engine Revolution Chart 22
Guarantee Details .. .. .. .. .. .. .. 23
INDEX TO ILLUSTRATIONS
Camshaft Engine
Timing Charts
Valve Extractor
Valve Grinding Tool
Fabric Oil Filter
Gearbox Adjustment
Clutch
Oil Bath Chain Cover
Amal Carburettor
Lucas Magdyno
Vernier Timing Adjustment
Wheel Alignment Gauge
Steering Head and Handlebars
PAGE
5
6
7
8
10
11
12
13
14
17
18
19
21
.. .. .. .. .. ..
.. .. .. .. ..
.. .. .. .. .. ..
.. .. .. .. .. ..
.. .. .. .. ..
.. .. ..
.. .. .. .. .. .. ..
.. .. .. ..
.. .. .. .. .. ..
.. .. .. .. .. .. ..
.. .. .. ..
.. .. ..
.. .. .. .. .. ..
.. .. ..
.. .. .. .. .. ..
.. .. .. .. .. .. ..
.. .. .. .. .. .. .. ..
.. .. .. .. .. .. ..
.. .. .. .. .. .. ..
.. .. .. .. .. .. ..
.. .. .. .. .. .. ..
.. .. .. .. .. .. ..
.. .. .. .. .. .. ..
.. .. .. .. .. ..
.. .. .. .. .. ..
.. .. .. .. ..
.. .. .. .. .. .. .. ..
.. .. .. .. .. .. .. ..
.. .. .. .. .. .. .. ..
.. .. .. .. .. .. .. ..
www.ajs-matchless.info

Assuming that the owner is already conversant with, and can ride a motor cycle,
a description of the control layout will be helpful and obviate those anxious few moments
when taking over a new or strange machine. First of all the Four Speed Gear Change, if
hand operated, has the following positions: Low or First Gear at the bottom of the Quadrant,
Neutral is next, Second, Third and Top follow on to the top of the Quadrant- With Foot
Operated Gear Change, first of all find Neutral position by moving the Pedal up or down,
then First Gear is engaged by pressing the lever downwards. Second by raising the Pedal,
and Third and Top Gears are engaged with subsequent upward lifting of the Pedal. The
opposite action is necessary to change to lower gears, the correct way of changing to lower
gears being fairly obvious—merely depress the Pedal downwards to the limit of its travel
to engage each lower gear. In the case of both hand or foot operated Gear Change, do not
impose any stress on the lever by attempting to wrench the lever from one position to another,
as by merely pushing the machine backwards or forwards the Gear Lever can be moved
quite easily to any position.
Handlebar Controls are situated and operated in the following way. Twist grip
Throttle Control—Right Handlebar opening inwards. Air Control lever—Right Handlebar
opening inwards. Front Brake Control Lever—Right Handlebar inverted lever. Clutch
Control Lever—Straight Pull—Left Handlebar. Exhaust Valve Lifter Straight Pull Lever on
Right handlebar. Ignition Control Lever—on left Handlebar—to advance move inwards,
retard outwards. On electrically equipped models the Dipping and Dimming Control switch
is fitted to left Handlebar.
Starring.
—Do not overflood the Carburettor, only depress the Tickler enough to
feel resistance by the float lifting. If Petrol runs out of the Carb. intake turn off the Petrol Tap
before kicking the engine over, but remember to turn this on again after the engine is started.
Starting is much easier if the engine is kicked over once or twice with the throttle wide open,
the air lever closed and the Exhaust Valve lifted afterwards, almost closing the throttle
more than 1/8 when attempting to sta rt the engine.—See Carb. Ins.—Pages 14, 15, 16.
On the Road.
—It does not occur to every rider to adjust the machine to suit his
personal requirements, although numerous make this their first job when taking over a new
machine. With the provision made for adjustment of the Saddle, Footrests, and Handlebars
to suit individual requirements it is possible to obtain a feeling of comfort and security.
Gear Changing.—
Riders will find that it is not necessary or desirable to complet el y
withdraw the Clutch when changing gear. After a little practice gear changing can be done
quickly and quietly if the throttle is left slightly open and the Clutch is only withdrawn slightly.
The gear lever should then be moved sharply from one position to another.
Braking.—
Educate yourself to using both front and rear brakes together, using the
rear only, invariably leads to skids on wet roads. On dry surfaces it is possible to apply
considerable pressure to the front brake control without any tendency of the front wheel to
skid, but exercise care on wet or slippery roads, and learn by experiment the maximum amount
of pressure that can safely be applied.
DRIVING INSTRUCTIONS
—3—
www.ajs-matchless.info

CAMSHAFT ENGINE DETAILS.
346 c.c. Model—Bore 70 m.m.—Stroke 90 m.m.
495 c.c. „ —Bore 79 m.m.—Stroke 101 m.m.
TAPPET CLEARANCES.
Inlet—16 thou. Exhaust—18 thou. When engine cold.
CAMSHAFT AND MAGNETO CHAIN SIZE.
Number of Rollers—Camshaft ax .230 86
—Mag. Chain ax .230 51
Piston Ring Gap—10 thou.
SPARKING PLUG TYPE AND SIZE.
Competition Engine
Racing Engine Lodge H.54—14 m.m.
Lodge BR.50—or BR.52—14 m.m.
346 c.c.
495 c.c. 6.8 to 1
6.5 to 1 7.5 to 1
7.5 to
1
11 to 1
11 to 1
COMPRESSION RATIOS AVAILABLE.
ENGINE SPROCKETS — No. OF TEETH.
346 c.c. Standard and Racing Solo
495 c.c. Standard Solo
495 c.c. Racing Solo
21 Sidecar 18
24 „ 21
25 „ 21
DISMANTLING AND ASSEMBLING : ENGINE
Cylinder Head Removal.—First remove Petrol Pipe. Carburettor complete (as this is
taken from the Cylinder Head remove Knurled ring from top of Carburettor Body and with-
draw both slides, leave these attached to their Cables and swing them out of the way).
(Extreme care should be taken not to damage the throttle needle whilst this is exposed);
Sparking Plug, Oil Feed Pipes to Valve Guides, Oil Feed Pipe from main Engine Pump to
Rocker Box and Oil Drain Pipe to Rocker Box Pump, also Exhaust Pipe Locking Ring, etc.
Next remove the four Pins holding the Rocker Box Pump and top Inspection Disc. Take
away the Pump drive and its retaining ring and the Camshaft locknut will then be visible,
withdraw the Cotter Pin from the nut, this can then be unscrewed. Prior to removing the
Pegged Plate which locates the Chain Wheel and Sleeve turn the Engine slowly over until
the top of the Compression stroke is reached; now unscrew the four Rocker Box Pins, and
withdraw the three that are free to come away, then the Rocker box is free, but when taking
this away see that the chain wheel is held in position by the tool provided in the tool kit.
The tubular portion of this can be used for pushing the Camshaft out of the Chain Wheel,
use two chain cover Pins for holding this tool to the chain cover. Six Cylinder Head Bolts
are now visible on top of the Head, also two nuts will be found holding the Cylinder Head
to the Barrel underneath. Remove all of these.
„ „ „
… … …
… … …
……………
……………
… … …
… … … … …
… … … …
…
—4—
www.ajs-matchless.info

THE A.J.S. " TROPHY" O.H.C. ENGINE.
—5—
www.ajs-matchless.info

VALVEANDIGNITIONTIMING.
—6—
www.ajs-matchless.info

The cylinder head can then be lifted up and off. There is no Spigot or washer on
the Cylinder Barrel, hut the Head must he lifted high enough to clear the two Cylinder Head
studs. If the Cylinder Barrel is removed do not prise this from (he Crank-case but place
the palms of the hands round the finning and rock the Cylinder from side to side and when
it starts to leave the crank-case lift upwards. Do not let the connecting rod fall heavily
against the mouth of the Crank-case or the crank-case face will be damaged. When removing
the Piston, only withdraw one Gudgeon Pin Circlip with the special pliers provided and then
either push the Gudgeon Pin out from the opposite side or insert a screw-driver inside the
Gudgeon Pin and bear the screw-driver to one side and turn the Pin slowly out of the Piston
Bosses. The Gudgeon Pin is a sliding fit in the Piston and Small End. When the Piston is
removed either remember the correct original position indicated by the remaining Circlip,
or take a sharp instrument and make a mark on the inside of the piston to indicate front and
back ; be sure to replace the Piston in its original position,
For the removal of the Valves we list a special tool costing 5s. 9d. Part No. XB3340;
and for Valve Grinding a Small Tool costing 1s. 6d. Part No. XB.3360.
The accompanying illustration shows the method of operation of both the valve
extractor and the valve grinding tool; although the Cylinder Head shown does not of course
belong to a Camshaft Model the operation is similar. For portability the valve extractor is
made to fold. Be careful to see that the portion of the toot which depresses the valve spring
collar is central before compressing the spring, otherwise it is almost impossible to remove the
split cones. An important factor to watch when replacing the valve springs is that the
collars are replaced underneath the valve springs. Whilst the cylinder head is dismantled
remove the oil feed nipples to the valve guides to ascertain that these are clear; the inlet
nipple, it will be noticed, is purposely restricted with a disc, so be careful to see that these
nipples are replaced correctly.
Re-assembling—After replacing the Piston, rotate the piston rings in, their grooves
until the respective gaps are at equal distances round the piston, and make sure that the
crankcase washer is still unbroken, otherwise replace. Lead the piston into the cylinder
by holding the piston as far round as possible with the thumb and first finger, at the same
time closing in the rings round the piston. The Cylinder barrel has a chamfer lead-in for
the rings to enter. When the cylinder is again on the crankcase tighten the cylinder nuts
down evenly, not independently.
VALVE EXTRACTOR.
—7—
www.ajs-matchless.info

NOCYLINDERHEADWASHERISUSEDONTHEA.J.S.CAMSHAFT
ENGINE.
Originallythefacesofthecylinderheadandbarrelaregroundin.andproviding
theyremaincleanandunscratchedcanbereplacedwithoutanyjointingcompoundor
attentionotherthanwashingwithpetrol.Ifhowever,eitherofthefacesaremarked,causing
compressionleaks,removethetwoholdingdownstudsbytwonutstogetheronthethread
ofthestudtounscrewthis,thensmearthefaceswithveryfineemerypaste,andgrindin
thesamemannerasinvalvegrindinguntilallthemarksareremoved.Besuretoremove
alltracesofemerypastewithpetrolafterthisoperation.
Actuallyitismuchbetterandeasiertogrindinthesefaceswhenboththecylinder
barrelandheadareawayfromtheengine;thereisthennodangerofemerypastefinding
itswayintotheengineandthecylinderheadcanberotatedfreelyonthebarrel.Whenthe
Cylinderheadisagaininposition,replacethenutstothestudswhichprotrudethroughthe
cylinderbarrel,followonwiththelongcylinderheadbolts,andlastly,theshortcylinder
headbolts.Tightenthesedowntogether,notindependently.Beforereplacingtherocker
boxmakesurethatthesmallhardenedcapsarefittedoverthevalveends,andplacetheone
rockerboxboltnearesttotheexhaustlifterintoitshole,thenlocatethethreadedendofthe
camshaftintothecentreofthechainwheel,afterwardspushingoutthetoolholdingthisin
position.Watchthattherubberwasherbetweentherockerboxandthechaincoversettles
intopositionproperly.
Whenthechainwheelisinpositionontheshaftandtherockerboxtighteneddown
itispossibletofeelthechaintension.Anyexcessiveslacknessafterthemachinehascom-
pleteda considerablemileagecanbetakenupbyfittingwashersofthecorrectthickness
undereachlegoftherockerbox.Itisessentialhowever,thatapproximately3/8in.or½in.
ofsidemovementalwaysexistsinthechain.
Asmallplugissituatedabouthalfwayupthecamshaftdrivecover:whenthisis
removeditispossibletoinserta narrowscrew-drivertoascertainthatthetensionerblade
isfollowingthechainandnotidleagainstthesideofthecover.
Providingtheflywheelshavenotbeenrotatedthepeggedplatecanbereplaced
throughthechainwheelandsleeve,butiftheflywheelsarenotintheoriginalposition,turn
theengineslowlyoveruntilT.D.C.ofthecompressionstrokeisreached:theholeinthe
sprocketandthatinthesleeveshouldthencoincidealthoughsometimestheshafthasto
berotatedslightlytobringthetwointolinesoastoreplacethepeggedplate.A rough
checkforthevalvetimingis,thatwiththepistononT.D.C.andthecontactbreakerpoints
justbreakingwiththeignitionleverfullyretarded,boththeholeinthechainwheelandthe
sleeveshouldbetogetherat50°totherightfromT.D.C.
HOWTOUSETHEA.J.S.VALVEGRINDINGTOOL.
—8—
www.ajs-matchless.info

WhenReplacingtheCarburettoralwaysrenttheslidesandcablesintoposition
beforere-fittingthistotheengine,otherwisedifficultywillbeexperiencedinlocatingthe
throttleneedlevalveintopositioninthecarburettor.Whenreplacingthecarburettorit
willbenoticedthatnoflangewasherisused,merelymakesurethatboththefacesareclean
andsmearwithshellacjointingcompound.Itisessentialtorefillor" prime" theoilpipes
withoilwhenre-assemblingtheenginetoensurethatoilisfed toallbearingswhenthe
Engineisstartedup.Shoulditeverbenecessarytoreplacea tensionerblade,firstdisconnect
alloilpipesandremovethecamshaftdrivecover; thedriveisthenvisible.Firstunhookthe
tensionerbladespringatthetop,andthebladeandspringcanthenbewithdrawnfromthe
bottompeg;whenreplacingverifythatthespringeyelocatesinitsgroovehalfwayalongthe
bottompeg.Thetopeyeofthespringalsofitsintoa grooveinthebladepinatthetop.
Ifitisevernecessarytoremovetheenginefromtheframe,timewillbesavedby
removingtheengineandgearboxunitcomplete.Todothisremovethetwotopfrontengine
bolts,slackenofftheothers,takeoutthetwoboltsrunningthroughthegearboxplatesand
saddlepillardowntube,andprovidingalltheotherconnectionshavebeendisconnected
thecompleteunitcanbetakenaway.
IgnitionTiming.—SeeMagnetoandMagdyno.—Pages18and19
Important.—Onlyadjustthevalvelifterlevercableenoughtoraisetheexhaust
valveveryslightlyfromitsseat,particularlyifa highcompressionpistonisfittedintheengine.
—9—
www.ajs-matchless.info

ENGINELUBRICATION
AllA.J.S.CamshaftEngineshavedrysumplubrication.OilisfedtoBigEndof
theEngineandtheRockerBoxbythemainpumpontheTimingChainCover.ThisPump
alsodrawsoilfromtheSumpandreturnsittothefilterintheOilTank,anillustrationof
whichisgivenbelow,althoughthisisforanothermodel.Byremovingtheplatedhexagon
pluginthetopoftheOilTankitispossibletowithdrawthefilterforthepurposeofcleaning.
TodothisimmersethefilterincleanPetrolbutalwaysmakesurethatitisthoroughlydried
outbeforereplacing.Thefiltershouldbecleanedevery500/1.000miles.Werecommend
thatalltheoilisdrainedfromtheOilTankevery4/5,000milesandthetankreplenishedwith
freshoil.ItisnecessarytotopuptheoillevelintheTankfromtimetotime,andobviously
itismosteconomicaltodraintheTankwhentheoilisatitslowestrecommendedlevel.The
correctOillevelintheOilTankbeingalmostuptotheendofthereturnpipe—donotoverfill,
otherwiseoilwillleakfromthefillercap—andneverletthelevelfallbelowtheTankbeing
halffull.WerecommendtheuseofCastrol" R " forRacingpurposesandCastrolX.L.for
generalandcompetitionpurposes.
AsmalladjustableoilpumpisfittedatthetopoftheTimingChainCover:thepurpose
ofthisistodraintheoilfromthesumpoftheRockerBoxandreturnittothecrankcasesump,
Toincreasethesuctiononthis,unscrewthelock-nutontheadjusterandturnthe
adjusterwitha screw-driverinananti-clockwisedirection,andtodecreasethesuction
viceversa.Aftermaking-theadjustmentalwaystightenthelocknut.This Pump iscorrectly
setbefore themachineleaves theFactoryand shouldseldom ifeverneed adjustment.
FABRICOILFILTER
—10—
www.ajs-matchless.info

GEARBOX
Gearbox.—To adjust the primary chain it is possible to swing the Gearbox bodily on
its lower fixing bolt, and to carry this out the following instructions should be observed:—
Slack off the centre nut on the foot gear change mechanism and to tighten the, front
chain first slack off the nut on the adjuster bolt nearest the Engine and turn the nut on the
other side of the anchorage in the same direction, i.e., anticlockwise, until the correct chain
tension is obtained. To ascertain this remove the small inspection disc on the front chain
cover, the tension can then be felt with the fingers. It is most important to leave approximately
ain. or ½ in. up and down movement. After the correct chain tension has been arrived at,
re-tighten the adjuster nut nearest the Engine and also the centre nut on the gear change
mechanism. Always make a point of adjusting the front chain first and the rear afterwards.
The illustration below shows a similar Pivot mounted gearbox but with hand operated gear
change ; the adjuster referred to, however, is clearly visible.
Should the gear positions of the foot gear change mechanism not correspond to
those of the gearbox index, the short rod between the operating lever on the foot change
mechanism and the striker lever on the gearbox, can be adjusted, as provision is made for this.
To check off the relation between the two first engage any gear and then remove
the split cotter and yoke end pin from the top of the Short Gear Rod ; if the two are correct,
the holes in the Yoke end and the lever coincide ; that is, when the lever is centralised, as a
small amount of free movement always exists in the lever. Otherwise unscrew the locknut
under the Yoke end and bring the Yoke end into line, afterwards tighten the lock nut and
replace the pins, etc. Only a small alteration to the length of the gear control rod is ever
necessary.
Should the Kick-starter return spring ever need replacing, unscrew the Pinchbolt
through the kick-starter crank, draw the crank from the splines, take away the Spring cover
and old spring, enter the end of the new Spring into the Gearbox end cover first, utilise a
pair of pliers to spring the end of the Spring into the locating hole in the Kick-starter Shaft.
To increase the spring pressure move the location of the spring end hole by hole in a clock-
wise direction until the correct tension is obtained.
Replenishment of the gearbox lubricant is very simple and the method fairly obvious.
The filler Plug is situated on the right band side of the gearbox cover plate. Priorto filling
with lubricant remove the level plug, which will be found about half way up on the gearbox
end cover, then fill until the lubricant starts to run from the level hole, afterwards replace the
level and filler plugs.
—11—
www.ajs-matchless.info

CLUTCH AND TRANSMISSION
The accompanying illustration shows a sectioned view of the Clutch fitted to Cam-
shaft Models. It there is a tendency for the Clutch to slip, make sure first of all that a little
play exists between the Push Rod adjuster and the Push Rod.
Illustration 9.
CLUTCH PARTS.
1.
2.
3.
4.
5.
6.
Clutch Spring Screw.
Main Shaft.
Clutch Thrust Pin.
Main Shaft Nut.
Locking Washer for Main
Shaft Nut.
Clutch Spring Screw Washer.
7.
8.
9.
10.
11.
12.
13.
Clutch Spring Box.
Clutch Spring.
Clutch Spring Box Plate.
Friction Plate.
Clutch Centre Plate Dished.
Clutch Outer Plate.
Clutch Sprocket.
14.
15.
16.
17.
18.
19.
20.
Clutch Back Plate.
Roller Bearings.
Clutch Spring Stud Nut.
Clutch Centre.
Clutch Spring Stud.
Clutch Rod.
Cork Inverts,
—12—
www.ajs-matchless.info

If the adjuster pin bears on the Clutch Push Rod, this prevents the Clutch Springs
from exerting pressure on the Plates. It is impossible to increase the Spring pressure by tightening
the Clutch Spring Pins, as these are screwed right home, and any undue pressure an these will break
away the heads of the pins.
In addition to the Clutch Push Rod adjustment, a clutch cable adjuster is provided.
This can be adjusted with the fingers, but make a point of tightening the locknut, otherwise
the adjuster may vibrate and gradually work hack, eventually causing the Clutch to slip
through absence of play in the Clutch Lever. Although the front chain cover contains an
oil bath, this does not necessarily mean that the clutch runs in oil, if the correct oil level is
adhered to, centrifugal force will keep the oil out of the clutch, although a certain amount
may find its way into the clutch, this in no way impairs its efficiency. Actually the Clutch
is intended to run dry. The method of dismantling the chain cover and Clutch for examination
or Clutch Plate removal is as follows: Remove the footrest arm and Brake Pedal, next the
Pinch Pin at the rear of the aluminium retaining band and the rubber seal strip. The outside
portion of the chain cover can then be drawn away leaving the Clutch, Chain, Shock Absorber
etc., visible. The Clutch Plates can now be withdrawn after removing the six spring bolts,
springs, thimbles and thrust pin. To remove the Clutch Sprocket unscrew the centre nut
from the shaft and the Sprocket will then come away with the Clutch centre. To dismantle
the Sprocket from the centre, unscrew the six nuts securing these two parts, but be aery careful
when taking them apart because there is a Thrust race of Ball and Roller Bearings between the two and
these will drop out if not carefully handled. When re-assembling the Clutch, the Ball and Roller
bearings should be placed alternately round the centre, and to keep them in position smear
them with vaseline or grease after replacing the nuts securing the Sprocket to the centre,
punch and slightly spread the end of the pins in the nuts to make sure that they cannot become
loose. The sequence of the Clutch Plate replacement can be seen clearly from the illus-
tration. If the distance Pieces between the two sides of the Chain Cover have been removed
see that these are replaced before re-fitting the outside portion of the Chain. Cover. When
replacing the Rubber Seal strip, smear Shellac Jointing on the inside of this. The ends of
this strip should coincide with the ends of the aluminium retaining strap. Replace the Brake
Pedal before the footrest arm.
When a chain is joined up with a spring clip, it is most important that the clip is
correctly fitted over the cover plate. The open end should alwaysface in the opposite direction to
which the chain travels. Fit this so that the plate and spring clip are on the inside of the chain,
i.e., next the spokes.
Replacing Chain.—When replacing a chain it will facilitate the fitting of the spring
link if the ends of the chain are encircling an equal portion of the sprocket. This also applies
to removing the spring link.
Back Chain.—Slack off the nuts on each side of back hub spindle and move the
wheel backwards by means of the adjusting screws in fork-ends. Care must be taken to
adjust each side equally or the wheel will be out of alignment (see adjustment gauge. Illus-
tration 19). Screw the spindle nuts up tightly again after the chain is properly adjusted.
It may be found that moving the wheel back has caused the brake to be " on. " This is
easily rectified by means of the brake adjustment
—13—
www.ajs-matchless.info

If the chain is too slack it is apt to " whip, " which intensifies the wear and tends to
break the rollers. If on the other hand it is too tight, a crushing effect is produced on the
rollers, and the whole chain is strained unduly.
The chain should he adjusted and kept adjusted, so that it can be pressed down in
the centre with the finger about ¾ in.
CARBURETTOR
The Carburettor fitted as standard to the Camshaft Models is an Amal. There are
four ways in which the quality of the mixture can be varied, these are as follows :
1.
2.
3.
4.
Alteration of Main Jet size (P) to adjust setting from ¾ to full throttle.
Needle position (C) in Throttle Valve ¼ to ¾ Throttle.
Throttle Valve cut-away on the air intake side (H) ¼ in. to ¾ in. Throttle (num-
bered on top of slide showing variation).
Pilot air adjustment (L) closed to 8Throttle.
—14—
www.ajs-matchless.info

When the machine is despatched from the Factory the Carburettor has been correctly
set, but if the machine is used under varying atmospheric conditions, slight adjustments
may be necessary. In the first case if starting is difficult and the Engine refuses to " idle "
evenly, slowly screw the Pilot Air Adjuster inwards, but if on the other hand the Engine is
inclined to " eight stroke " at slow speeds, screw the Pilot Air Adjuster out until this disappears,
A point worth mentioning about starting is that the Throttle Stop (illustration) should be set
so as to lift the Throttle Slide slightly off its seat, the twist grip can then be left in the
" closed " position when starting the Engine. The next adjustment is carried out by fitting
a throttle Valve with a different cut-away. If when opening the Throttle spitting back
through the Carburettor, or misfiring occurs, this indicates a weak mixture. To correct this
fit a Throttle Valve with a smaller cut-away.
Black smoke from the exhaust or "eight stroking" at low-intermediate Throttle
openings indicates richness, fit a Throttle slide with a larger cut-away.
As a guidance each throttle Valve is stamped with two numbers. The first indicating
the type of Carburettor, and the latter indicating the amount cut-away from the intake side
of the valve in sixteenths of an inch. Thus—6/4, is a type 6 Valve with ¼ in. cut-away.
The necessity for alteration to the needle position may be checked in the following
way; Start the Engine and open the air lever to its fullest extent, open Throttle control
half way and notice whether the exhaust note is crisp and the Engine lively, then close air
lever slightly, if this results in increased Engine speed raise the needle to the next position
in the throttle valve. On the other hand, if the Engine speed does not increase when the air
lever is closed to about half way and the throttle opening increased, or if any tendency to
" eight stroke " occurs, then lower the needle to the next position in the throttle slide. To
alter the needle position pull away the small spring clip locating the needle in the Throttle
Valve and afterwards force this home again. For a Semi-Automatic setting where the Rider
intends to use the Air Lever judiciously and studies extreme economy, lower the needle one
groove further after carrying out this range of tests. For speed work, the Main Jet size may
be increased by 10% as the air lever should always be full open on full throttle openings.
STANDARD CARBURETTOR SETTING
Main Jet
size.
33/7 160
33/10 200
Needle
position.
3
3
Cut away.
6/4
6/5
RACING CARBURETTOR SETTING
For 59/50 Petrol Benzol and Engine Compression ratio 7,5 to 1.
Main Jet
size.
33/7 52
33/10 58
Cut away.
4/5
4/5
Bore size.
1z
1x
Carb.
Type No.
N.M.8617
N.O.3131
For Discol R.D.1 Fuel, and Engine Compression ratio 11 to 1.
Main Jet
Size,
33/7 55
33/10 65
Valve No.
12
12
Bore Size.
1.06
1.18
Carb.
Type No.
N.M.7091
M.D.992I
—15—
www.ajs-matchless.info

On the Racing Camshaft Models, an Amal Racing Carburettor with Twin Fuel
feeds is fitted. When tuning this for speed work select the main jet size which gives maximum
power and speed with the Air and throttle full open. The correct size is readily found by
moving the air lever at full Throttle openings : any increase in power obtained by half closing
the air lever indicates that the jet size is too small. Loss of power on closing the Air Lever
slightly shows that the main jet is rather too large. It is far belter to err on the rich side with
Carburettor settings. Weakness " Cooks " Sparking Plugs and other Engine parts.
Idling or slow running is governed by a knurled screw on the side of the Carburettor;
for Petrol Benzol it should be unscrewed about two and a half turns, but for Discol R.D.1
fuel, only about half a turn. Always adjust this control so that a clean pick-up and good
acceleration are obtained. From one eighth to three quarter throttle is governed by the
throttle cut-away; this is indicated in the way explained previously. Three quarter to full
Throttle is governed by main jet size.
LUCAS MAGNETO AND MAGDYNO LIGHTING SET
When Camshaft Models are not fitted with Magdyno Lighting a Lucas Racing
Magneto is fitted. Magnetos have now reached such a stage of perfection that trouble is
seldom if ever experienced with these. Their condition, however, does affect the performance
of the machine considerably. If any trouble is experienced with the Magneto this will usually
be traced to either the High Tension pick-up or the contact breaker. Should starting become
difficult and Ignition is suspected, inspect the following points, remove sparking plug, hold
this against the cylinder with the high tension lead attached to the terminal and kick the
Engine over (be careful to see that the hand is nowhere near the terminal, and that the plug
body makes contact with the cylinder or a shock will be felt) if there is no spark at the points,
take the terminal away from the plug and hold this about 1/8- in. from the Cylinder, at the same
time kicking the Engine over; if a spark is now visible the fault is in the Sparking Plug. Check
off the gap between the points, this should be 20 Thou and if necessary adjust them by either
tapping the electrodes together or springing the outside electrode away with a thin screw-
driver. If the plug still refuses to spark, unscrew the centre from the plug body and clean
the mica insulation with a Petrol soaked rag. Make sure when assembling the plug that the
gap between the points is correct. Should it be impossible to obtain a spark from the High
Tension Terminal against the Cylinder, first remove the High Tension Pick-up and examine
this; if any carbon or dust exists wipe this away, also take a pencil or similar object, cover
this with a cloth and insert into the hole left by the removal of the Pick-up, press this lightly
on to the Slip ring, and to remove any carbon which exists rotate the Engine with the Kick
Starter.
Should this not have the desired effect turn to the contact breaker, A Spanner is
provided in the tool kit for adjusting the contact breaker points and removing the contact
breaker centre pin. Take the Contact breaker out bodily by first unscrewing the Contact
breaker Centre Pin and Rocking the Pin from side to side in the centre of the Contact Breaker,
it will then leave the taper hole in the Armature shaft. Now that the Contact Breaker is free
turn the Rocker Arm locating spring and prise the Rocker Arm off its Pin; the Points will then
be visible. If these are pitted or show indications of scaling, file the surfaces of both evenly
with a smooth file, afterwards smooth with fine emery cloth.
When replacing the Rocker Arm on its Pin see that this is an easy fit; a tittle grease
should be smeared round the pin. Be careful when re-fitting the contact breaker to see
that the keyway on the taper of the contact breaker body locates properly in the Armature
shaft before tightening the Centre Pin.
A Gauge is provided on the side of the Contact Breaker spanner for checking the
gap between the points.
Lucas Magdyno.—The previous information covering the Lucas Magneto applies
also to the Magneto Portion of the Magdyno. The Dynamo portion of the instrument is
detachable and can be removed in the following manner :—
—16—
www.ajs-matchless.info

Unscrew Dynamo leads (M and L) Dynamo securing strap (0) and Nut from Drive
cover, the Dynamo is then free. Wrap some insulating material round lead M, otherwise
the battery will be discharged if the bare end touches any portion of the machine; occasionally
refill the lubricator fitted to the drive cover with grease and screw the cap down. In the
event of the Dynamo ceasing to charge, remove the Dynamo end cover and observe whether
the cut-out closes when the engine is " revved up." If it does not, verify that all three brushes
are settling down on the commutator properly. If after checking alt the leads and connections
as being tight and the dynamo still refuses to charge, take the machine to your nearest Lucas
Depot for attention. Never attempt to push the points of the cut-out together, this will result in a
dead short. If you are compelled to run the engine for any length of time without the Battery,
or if any trouble is experienced with the Dynamo withdraw the brushes from their housings
and clip them under the brush springs or remove the Dynamo altogether until this can be
attended to either by the nearest Lucas Depot or an electrician. Both the Lucas Magneto
and Magdyno are intended to run without attention for at least 10,000, after which the In-
strument should be dismantled for the bearings to be repacked with grease.
A—Securing spring for contact breaker cover. B—Contact breaker cover. C—
Fibre heel. D—Contact points. E—Locking nut. F—Adjustable contact point. G—Con-
tact breaker fixing screw. H—Locating spring. J—Nut securing brush eyelet, K—Cut-out,
L—Cable to headlamp switch terminal marked FI. M—Cable to headlamp switch terminal
marked +. N—Cable to sparking plug. O—Dynamo securing strap. P—Spring lever
holding brush in position. Q—Carbon brush. R—Pick-up. S—Securing spring for
pick-up. T—Cover. U—Earthing terminal. V—Screw securing dynamo strap. W—Cover
fixing screw.
—17—
www.ajs-matchless.info

Timing.—If the magneto has been removed from the machine it will be necessary
to see that it is timed correctly after it is refitted.
The sprocket on the armature shaft of the magneto is supplied with a vernier timing
adjustment, which allows a very accurate and
certain method of fixing the drive after the
correct setting has been arrived at. The setting
of this vernier adjustment may at first sound a
trifle complicated, hut in reality it is perfectly
simple. Filled to the armature shaft of the
magneto is a sleeve (1), which has thirteen holes
ranged in a circle. Fitting over a collar on this
sleeve is the chain sprocket (2), which has
twelve holes similarly arranged. Now on the
sprocket on engine driving shaft and on the
magneto shaft will be found an arrow. These
must point to each other before anything else is
done. The first thing then in timing up is to
set these two arrows so that they face exactly
towards each other. To do this turn engine
over until the arrow on the driving sprocket is
pointing directly towards the arrow on the mag-
neto sprocket. This latter should he held free
in the fingers and moved a tooth backwards or
forwards in the chain until the correct setting
is arrived at. When this is so, place the magneto
sprocket on to the sleeve, and turn the armature
shaft of magneto until a mark found punched
over one of the twelve holes on the sprocket
exactly registers with a similar mark on the out-
side of the collar of the sleeve. It will now be
found that the marked holes in sleeve and
sprocket respectively exactly coincide, so that
all that has to he done is to push the peg
washer (3) into these holes, which effectively pre-
vents the sprocket from moving from its correct
setting, and tightly screw up the sleeve lock
nut (4), which can be done without fear of
the timing shifting in the process, as is often the case with other methods. As a means
of verifying the timing, or if the sleeve (1) has been removed from the magneto armature
shaft, set the piston its correct distance from top of compression stroke (see ignition timing
for details), making sure it is not on the exhaust stroke,
With the piston in this position take off the sleeve lock nut on magneto sprocket and remove
the peg washer. This will leave the armature free from the engine drive, but still connected
Illustration 5.
VERNIER TIMING ADJUSTMENT.
CONTACT BREAKER.
—18—
www.ajs-matchless.info