BSA B31 User manual

'1sA
Instruction Manual
i,loddr l916-1955
rltl lr c.c" O.H.Y.
ln l3{, c.c. O.H.V. Competition
l!2 ltO c.c. O.H.Y. Gbld Star
l33 5{l0 c.c. O.H.V.
I134 5( c.c. O.H.V. Competition
834 s(Xl c.c. O.H.Y. Gold Star
+
PART No. 00-4010
if
I
I
i

Instnrction Manual
ZsA
B Models
r946-1955
B.S.A. MOTOR CYCLES LTD, ARMOURY ROAI)
BIRMINGIIAM, IT
Srdic!, Sp$.. tpd R.pdd D.pst|roa-
WAVERLBY WORKS. BIRMINGIIAM IO
TehDh.t t: B:ttnliEhan vlcrori. 37ll
T.EsrMt ad Caårrrj "sErsBRv." BkbinShal|.
BS.Å. Motot CtcLs L.d. t.etw tk rlsh, .o altz, th. d.tlsrt o
@t @Nttuctiotul d.talls o! theit nøaItutu..t at ø,
tlm. wllhoat slriw noti...
' Copyiish! B.S.A. Co. Ltd.
P.tntal i" Ealdd. M.C.6l8-A-5.
t,
Reprintd July 196l

This Instruction Manual is intended to acquaint the
B.S.A. owner with details of the controls, general main-
tenance and technical data which may be required for
Dormal operation of the machine.
It does not contain the information necessary to carry
out complete stripping for major overhauls, but if any
owner feels he is competent to ca y out this type of work
a Service Manual and an illustrated, Spares Catalogue
for this machine can be obtained fiom your B.S.A.
spares stockist or local distributor.
Owners in the British Isles can obtain these publications
direct from B.S.A. Motor Cycles Ltd., Service Department,
Waverley Works, Birmingham 10. The Service Manual is
priced at seven shillings, plus sixpence postage, and the
Spar€s Catalogue is ijve shillings and sixpence, plus
sixpence postage. Always quote full engine and frame
numbeE when ordering these publications.
CONTENTS
Air CIeJrer (Competidoo and Plueer Model3) ..
Air Cl€aner (seidcins Aim Modcls)
Battery
Bråkes
Cdburer,.r
cabu'ette.('Monouoc') .._ ...
cadtralstad ( enrv , tilfr..
Clqnirs
Clurcb
Conllols
Cylinder Hesd and Barol Removal
Cylinder H.rd ånd Bådel Rcmoval(Cobpetition)
Cylinder Heåd ard Barcl R.moval (Gold star)
Data
Drivinc
D@rb;nisins
Dtnrmo
Fooi Gcar-chsgo .. ..
Forks
Gcebox
Hub!
Ignirion Timins . . .r ..
Lmp.
LnbricRtion Chan -. .,
Lubricatioo sylt.nr ,.
.. 35
.. l7 62
.. 17 32
.. 38
.. 3E
.. 919
19 30 31 32
.. 16
.. 18 2E
., 4t
.. ,18
., 50
.. 4 5
.. 9
., 42
'' 63
.. 2I
.. 17 t9
,. 17 20
.. 28
.. 6t
.. 36 37
,, 64
.. l8
.. 16
.. 43
.. t7 46
.. 46
'' ll
.. 7l 76
., 33
.. 48
.. 49
.. 24
.. 4 5
.. 26 42
.. 26
.. 50
.. 46
.. 6E
.. 69
.. 70
-. 66

P.trol tek €paciry Gallons) ..
P.trol tank cåpåci'ly with Ssinsils am susp.nsioD
(..llom)
oil tiil cåpåcily (DinB)
Tbitd
First
'i':t
2 {s5 c.c.} 8 (225 c.c)
8 (225 c.cJ - 8 (225 c.c.)
88 88 88
,t99 199 499
.@3 .003
6.5-1 6.8-I
:$3 :3å3 :3å3
Cl()g 65' aftd bd.c.
clo3o3 25c aftd t.ilc.
Ll0s
.020
.ol8
sTD, S.A.
s.o 5.0
6.59 6,05
r0.3 8.?9
14.9 12.90
3.25-t9
3.50-19
l7
IE
TECHNICAL DATA
832 codD. 832 G's.
2ot3
- tot4
-5t
lr
8 O25 cc.) 8 (225 c.c.)
7l 7l
88 88
3:E 348
.@3
6.5-l
.otz ,ol2
.008 .008
25' boforc rdc.
65' bGfor. b.d.c.
7.05
t0.25
16.45
22,3
2.75--:21
4.00-19
T
l6
tt:|l
3
4'
5t
I
2 (55 c,..)
8 (225 Gc.)
7l
8E
3d6
.003
6,5-l
.ot2
.(r08
7lt6
Lt0s
,020
.018
sm, s.a.
5.6 5.6
7.38 6.77
11.5 9.86
t6.7 t4.42
3,25-t9
3.25-t9
t7
22
B3l CodD, 834 G.S
2or3
- '2ot1
B!:,
3
4L
69
t7
l9
t50
150
26
200
70
93
t9
l9
200
r70
2@
210
.020
.018
2l
22
66 o. 68
9? or 9E
7lt6
NA8
.020
.0 tE
9l
l6
t50
150
7ll5
.020 .020
.018 .018
5.64
8.21
iiiio
2.75-21
4.00-19
22 2l
15 18
69 57 to 69
91 97 or 9E
16'
2@
l?0
' 5.. sp.cial iwttuctlont for
Så.' indiøIAi Eodcb 6lt d tirh Sc/irsirs Am R.4 Suspco3ior.
t NoTE.-Th. rccomeDdcd iDfation Drts3@s at! ba!'d oo
franas (qc€Dt for Cold Sla.s) witb a riddt iv.islt of l40lb. If lhc
ftont lvt.t'Add on lb. oer .q. in. for evorv 28lb incroas. sttovo
above i40 lb. lf th. 6ac-hino i! 6tæd wilh swinene dm roar sue
is carricd, the ætual load beding upo! cach ivrc should bo dot6r'
Load snd PBsur. Sch€dula
GoA Stut nodels on Pas. 49.
Noi.: I pint - 5f.ot. - 8 tabL6pooo3.
CoEo. mod.b witb lisid framB ånd otltd 'B' 6odcb Fith JtlgosFr
iGri*-åiÅr .'itn' iro tb.. idcr.e lhe t{rc prc'surg a fo[os!:
'r/'[ rr. Aiar rv,e: Add one lb. por 3q. i.. for overv 14 lb. ircl'åso
bdsion {8 lb. h.avier). olber cxtra. or a piui9o på$.oser.or |!9s38€
inin.d aid tho orusurd incrca3od in acco.danc. w|tb rn. uudo9
r

IGNITION
* LIGHTING
STEERIN6
THE CONTROLS
SPEEDOMETER
HORN BUTTON
TTIE CONTROLS
IIANDLEBAR CONTROLS
Twist Grip Throttle.
Controls the engine speed. To open the throtde (r.e.,
to increase the engine speed) turD the grip towards the
rider. Full movement about one-qlrarter of a turn.
Front Brake.
The lever is on the right bar, below the twist-g p
throttle. Pull the level towards lhe bar to apply the
bBke, and note that this lever operates the front brake
only.
Carburettcr Air L€Yer.
On the right bar, and controls the supply of ak to
the carburetter, allowing the mixture of air and petrol
to be varied as conditjons require. Pull touards the dder
to open (i.e. to inc{ease the supply of air). Norrnal
running posilion fully open,
Hom,
The conlrol butlon is Jittcd on the back of the front
brake lever.
Clutch LeYer,
I-arger lever bclow thc left bar. Pull towards the bar
to dcclutch (i.e., to disengage the drive between the
engine and the rcar wheel). As the clutch lever is slowly
released the drive is restored gradually. Always declutch
when changing gear.
Dipper Switch.
Fitted on the back of the clutch lever, and actuates
the double filament bulb in the headlamp giving either a
normal or dipped beam.
Ignition Control.
Small lever on top of left bar. Controls the advance
and rctard ofthe spark produced by the magneto. Nomal
running position is fully advanced (i.e., lever moved
forward into the closed position. (See page 9 for starting
the engjne, the lever should be slightly retarded.
FOOT GEAR CHANGE
i/DowN\
" / .,'i'\
{ q+. I
\ --'""',, /
* \J,"--l
(oPqhdi^aiord'rcv)
Fig, 1, The Controls

Exheust Vålye Lifter (not illustrated in Fig, l).
Small lever under left bar. Pulling th€ lev€r up towuds
the bar opens the exhaust valve, releasing the com-
pression in the combustion chamber and enabling the
engile to be rotated easily,
FOOT CONTROLS
Rear Brake Pedal.
On the left hand side of the machine, and opemtes the
rear blake only.
Gear Chånge Pedal.
on the right hand side of the machine, and is used to
efect the change from one gear to anothei. To engage
fust gear from the neutral position, the pedal is moved
upwards. Second, third, and top ge,us are engaged by
movinS the pedal downwards. The pedal autoriatically
rEturns to the central position, rcady for the next gear
change. When engaging a gear the pedal should be
moved to its extreme limit, since the geår change is of the
positive-stop type.
Kickst4rter Pcdal,
Also on the right hand side of the machiDe, but is
situated behind the gear change pedal. Depression of the
kickstarter rotåtes the engine. See instructions on startiog
the engine. GENERÅL
Petrol Tap,
The t4p is of the push-pull twe, and is located under
the rear end of the tank. To tum the petrol on, pull the
serrated button out. To operate the teserve control,
totate button to right and pull out to lock in position. To
turn the petrol ofr reverce the above procedure.
Steering Lock (except Comp. and G. Stars).
Do not introduce oil into the keyhole as this may
clog the wards and wash away the spe€ially prepared
lubricant inserted before assembty. However, after con-
siderable mileage or under adverse weathet coaditions a
few drops of thin machine oil may be applied to the
periphery of the moving drun.
' Lighdne Switch.
On the left of the headlamp cowl ard cont ols the
lighting of the lamps as indicated by the following matk-
ings:- H-Head, tail and sp€€dometer latrps. I-Pilot'
tail and speedometer lamps. oFF-LiShts not in use but
battery on chargp.
I Ammet€r.
On ricfit of the headlamp cowl, Enables the rider to
see at a glance whether the battery is being charged or
discharged.
a Speedometer.
This is set in the headlarnp cowl. The trip can be turned
back to zero when the spring loaded flexible contrcl undet
the spe€dometer is pulled out and twisted ill a clockwise
dir€ction. The control automatically rcturns to its
original position, i.c. dise[gaged.
. On Competition ard Gold Star machines th€ lighting
switch, alrrmeter and speedometer ate centmlly mounted,
the fonner two in a panel on top of the headlamp and the
latter bolted to the top yoke.
Cetrkal Stand.
This is of the spring-up type and so designed that wheD
the machine is pushed fonvard ofr the stand, the latter
spdngs upwards and is automatically retained clear of
the road. DRIVING
Prelimimd€l.
;. 1 Before taking the machine out for thc first time, it is
',4 ressenlial to examine lhe oil tank, to ensure lha! an ade-
' quate supply of oil is available. The lank has a working
capacity of 3* pints on competition models, 4l pints on
plunger 'B' models, and for machines fitted with swinging
arm rear suspension 5I pints, Use only high quality
lubricants as recommended in the chart on page 36.
Examine also the rcmainder of the lubrication points
and verify the quantity of oil in the gea.rbox arld the
pdmary chain oil bath.
To Stårt the Engine.
It will help in balancing the machine if you stand astride
it when first attempting to start. Make sure that the gear
contlol is in the neutral position, i,e., between first and
second gear. Note that if the machine is ir gear it will
move forward wheD the kickstarter pedal is depressed.
If the engine is cold, first depress the cårbuetter ticklea
momentarily. Oosc the air lever, r€lard the ignitiotr

slighlly and open the twist-grip a small amounL Depr€ss
the kickstarter ped4l until comp.ession is felt, nise the
crhaust valve lifter and depress the kickstarter fredal a
little more, Release the valve lifter. allow the kickstarter
pedal to letum to the top of its stoke aDd then give it a
vigorous kick downwards.
This starting procedwe should alwaF be adopted as it
arllows the engine to gather sumcient momentum to over-
come the resistance of the next compression stloke,
Nore that while it is necessary to close the ah levea
when startiog from cold, this should not be necessary
when the engine is walm.
During normal ruoning th€ air lever should always
be kept fully open, although a slight gain in power at
low speeds on hills Eay sometimes be obtaiDed if the
levet is closed a very small amount.
The ignition lever should be fully advanced for normal
running. It may havc to be retarded slightly if the engine is
under an inc.eased load. The rrtanipulation of this control
is largely a matter of experience.
'lo engl|ge Filst Cear.
I)cprcss the clutch l€ver (i.e., declutch), and move the
gcnr change trcdø,| pwards to its limit. ff difficulty is
cxpcrienccd when engaging fiIst gear when stationary, rock
the rnachine backwards and forwards mahtaining slight
pressure on the gcar change pedal until the gear is felt to
cngage.
To Molc Ofr.
Open the throttle slightly aDd gently release the clutch
lever. As the clutch engages, open the throttle a little
turther, and when the clutch is fully engaged the machine
cao be accelerated to a suitabte road speed, ready for
ohanging into the next gear.
To ChrIge Gear (Up).
Close tho throttle, disengage the clutch and prese
the gea. change pedal downwards to its limit, all these
operatioN being p€rformed simultaneously. Engage the
clutch and re-open the throttle together, immediately after
changinS. lvot?. Violent pressure on the gpar chango
pedal is neither ne.€ssary Dor desirable.
To Chstrg€ Gc{r (Dortr).
Open the throtde slightly, disengage the clutch and
raise the ge3r changs p€dal upwards to its limit, all
these operations being performed simultdFously. Re.
cngage the clutch immediately.
Not?.-The above moverDelts zue quito easy to pedotn
aDd a litde practise lrill ctEure a lapid atrd quiet gear
change, When charging gear, either up or down, it i9
plgferable-aft€r moving the pedal-to hold it mom€n-
tarily itr position with the foot unril after the clutch
lever has b€en released, when the gears will b€ felt to
engage, Do not use aD excessive opening of the tbrottlc
when starting, and do not allow the engine to racE when
st4tionary. Usc the tbrottle cootrol to govem the sp€ed
of the Eachire, e,9., vhen descending a steep hi[, if a
lowet gear is eDgaged and the tbrottle closed, the engift
will contol the speed of descent. Oo very geasy ro4d0
the use of the enSine as a brake ii to be advocated,
particularly in conjunction with a change to a lower geaL
It is never advisable, except in cases of emergercy,
eitåer to accelecate or to btake fierc€ly; when thc roadi
are grcasy both are extr€mely dangerous.
TIINTS ON 'RTJNNING-IN ' A
NEW MOTOR CYCLE
The dder who has just purchased a new machide will
do well to remember that all the intemal parts are just
as new as tho enamel atrd plating which can b€ se€q
aod that they must be well "run-in" befoæ the eogioo
ca.a be given aoy really hard wo*.
The "ruDning-in" process is the most important pcriod
in the life of the engine, and the handling it rccsiv€s
dudng the frst 1,000 to 1,500 miles will determine tho
service it will provide in retum.
It is advisable not to exceed half tbrottle in any gear. Il
excessive speeds aae used there is risk of piston seizuro
and other troubles, and in any ev€rt until the &achine
has been "ruo-io" it caDnot be expected to give its b€€t
perfonnance. In particular, avoid rapid acc€leration,
cspecially when the edgine is not under load atrd do not
l0 u

Ii'
I
allow the engine lo lilbour orr hills in a hiah acitr whcn I
change to a lower gear would casc the load on thc engir)c.
Do not let the oil level in the tank get too low, as
economy in oil may prove very expensive at a later date,
Running consistently with the oil level too low may couse
the oil to become unduly hot. It must be lemembered
that the oil cools as well as lubricates, and a new enginc
tetrds to run a little hotter lhan one that is well "run-in."
One more tip that is worth while-add a small quantity
of upper cylinder lubricant to the petrol each time the
tank is rcplenished- If this is difficult to obtain, add about
atr eggcupful of engine oil to every 2 galloDs of petrol.
HOW THE LTJBRICATION SYSTEM
WORKS
The engine lubication system (see Fig. 2) is of tho
dry sump type operated by a double gear punp, situated
in the bottom of the crankcase on the right-hand side.
All oilways are intemal except for the supply and letum
pipes from the tank and the oil fe€d to tho valve rockers.
The oil ffows from the tank-through a 6lter in the tank
to the supply pump (the inside crankcase union) aud
thence past the pressure valve ,4 to the oilways feeding
|he cåm spindles and along the hollow mainshaft to tbe
big-eod bearing.
After lubricating the big-end alld circulating through
the engine in the folm of mist, the oil &ains dolln
through a filter in thc bottom of the qankcase, from
which it is drawn by the rctu.n pump (lower pair of
gears) past ball valve q and delivered up the retum
pipe (outer crankcase union) to thetank, Oilis fed through
a union situated in the pipe betweeD the rcturD pump
and the tank, to the rooker spindles, ard after lubricating
the rockers and enclosed valv€s, is retumed to the clank-
case through an external oil pipe attached to the base of
lhe inlet valve spring housing. In the case of aluminium
engines, the oil retums to the crankcase via the push aod
lunnel.
Incorrect seating of the ball valve I may allow oil
to transfer from the tadk to the engine whilst the machine
is stationary. In this event, unscrew the plug retaining
the valve, and retuove spring and ball. Clean the ball
and its seating and replace. If nec€ssary, to ensure a close
fit between ball and seat the ball should be rcplac€d on
its seating and dealt a shary blow with a light hammer
and punch to make certain that the ball beds on the seat
in a satisfactory manner.
If the ball valve c should get stuck in its seating, there
will be do retum of oil to the tank. To correct, remove the
cover plaie I below the pump, insert a pi€oe of wire iDto
the valvc orifice, and lift the ball off its seating to free iL
To check the flow ol oil in the lubricatiDs system, reftove
the tank filler cap whilst the eogine is runnhg. Oil should
be seea issuiog from the retum pipe from the øankcåse.
Any restriction in the pressure release pipe (see Fig. 2)
in the tank will cause an increase in pressure inside the
oil tank, and will result in leakage of oil at the 6ller cap.
This can be rectified by inserting a lenglh of flexible wire
into the pipc at its lower end (just in flont of the r€ar
mudguard) and pushing the wire right up the pipe, thus
cleadog any obstruction. In the cas€ of Comp. models
atrd machines with swinging arm rear suspemion which
are 6tted with an oil brcather tower (Fig. 2a) it is only
oecessary to keep the short length of tube clear which
projects horizontally from ii under the seat.
To remove the oil tank filter for cleaning on Comp.
models and machines fitted with plunger frames (se€
Fig. 2) remove the oil pipe banjo union plug at the bottom
of the tank. The filter will come out with the plug. On
models 83l and 833 it is preferable to remove the toolbox
first. This is secured by three nuts and bolts, one through
the mudguard valance and two through the short verticål
strip oD the chainstay. On swinging arm models (Fig. 2a)
it is not necessary to unscrew the oil pipe union, the oil
tank filter being attached to the larg€ chromed drain
piug screwed in the side of the tank, The supply pip€
which will be seen wher the drain plug is .emoved, draws
its oil rhrough the filte!. The filter should be placrd in a
oan large enough to cover it with petrol, and thoroughly
washed. Before rcplacing make sule that it is quite dry
of petrol.
The pump filter can be nithdrawn after removing the

\
Pressure
valve
oil
return
ripe to
crankcase
Double
gear typ€
oilpump.
A'l,r,aQ
Cover
plate B
Diaetum showing ho$, oil is circulated
from thc tank throughout the engine and
rctøned to the tank.
t5

cover plate and should be rhoroughly washed with peEol,
dried and r€placed.
Note.-The pump ls ltdepeodeotly EoEnted atrd 8hould
not be disturb€d.
PERIODICAL MAINTENANCE
WEEKLY.
Cleanldg. Obviously regular and thorough cleaning
will keep your machine looking smart aDd will help to
rctain both its new appearance and yalue. But it helpr
also to lengthen its life and maintain efficiency if the
clcaoing process is caFied out correctly.
Take sperial care to plevent dust and grit flom worki[g
into such parts as hubs, carburettet, magdyno, brakes
and gearbox,
To rub dry and cak€d mud from the frame, tank and
rnudguÅrds meaDs that the enamel on these parts will b€
subjecled to an abrasive action which will quickly destroy
thc polish. Soak the mud first, and then float it ofr with
copious supplies of clean water supplied either with a hose
or a spon8c. If a hose is used, take care trot to direct th€
ttrcam of \a,ater directly on to the hub b€ariDgs, magdlmo
or c{tbulcttcr.
Whcn oll dirt is removed dry and polish ofr with a
clcsn dustcr.
Thc cnginc and gcarbox are best cleaned with brush
and paraffin, and dried ofT when clean wirh clean mg.
On Iron engines an occasional coating of the cylinde!
head and fins with cylinder paint prevents rust formation
and also helps heat radiatior.
Oil Tqnk. Inspecl the level of oil. It should never bc
allowod to fall below the level marked on the outside of
tank. When topping-up, do not fill the tank completely;
leave about one-inoh margin betw€eD the oil and top of
tank, If this plecautiod is not observed, it is possible lhat
oil will s€ep from thc Rller cap. Id the case of new
machines, draia the tank after the first 500 and 1,000
miles as explailed on page 18,
Tlres. Examine carefully for cuts and remove any ffints
or metallic scraps which may have become embedded in
the cover. Check the pressurcs with a gauge, and innatc
to corrcct prcssure if necessary. (Sce pages 3 and 4.)
t6 l7
Ste€ring H€ad. Give two or thrce sffokes of the Sre3se
gun.
Brake Pedå|. Give two or three drops of oil occå6ionally.
Reår SuspensioD. (Plunger Type). A few strokes of the
gease gun.
Control Joitrt$ and Exposed Cables. A few drops of oil.
Sadde No6e Bolt One or two strokes of the grease guD.
Blttery. Top-up as oftetr as necessary to maiDtain lcvel
of elecholyte one-qua.rter inch above top of plates.
ALWAYS USB DISTILLBD WATER WHEN TOP.
PING UP. This oan be obtained cheaply at any Sarage
or chem.ist's shop (see page 62).
To gain access to the battery oD machines fitted with
swinging arm rcar suspension, remove the two bolts under
the dual seat at the rea.. The seat can then be drawD
backwards out of its front locatiDg grooves and clear of
the machine revealing the battery. Remove the two small
bolts holding the battery strap over the battery and
unscrew the battery terminals. The battery can then be
lifted out.
c"a"t *. Elåffih" oil level and toD uD if necessarv.
The oil is added rhrough lbe filler cap .qf,!ff,i!$-o4, the
Æ,JlrÅ'ht lhand side of the box, rhe holi {&(fr{Whre
-'''o'dffClfi,in.O oil level. On Comp and Swinging Årm
models the gearbox is fitted with a level plug, see K,
Fig. 13. In the case of new machines, drain the gearbox
after the first 500 miles as explained on page 19.
EVERY I.OOO MILFS.
Hubs. Inje.t gxease through tåe nipple in the c€ntre of the
hub. Do not over-lubricate as gease may be forced on to
the brake linings and cause ineffective brakes, Three or
four strokes of the geåse guD should be ample. Do Bot
lubdcste with oil.
Steering Head. Lift machine and place a box und€r the
grankcase so that front wheel is clcar of the ground.
T€st for play in the steedng head by trying up-and-down
movement. Che.k also that ste€ring is free (i.e., that the
ball race adjustmetrt is not too close.) If necessary,
adjust ås explained on page 2A.
i

BraLe Cam spturtle6. A few diops of oil is all that is
required. (8 in. Front Brake (nipple) one stroke oferease
sun.)
Trppet Adjustment (for Gold Star models see page 50).
Cheak when engine is cold. The corrcct method of
, t checking and adjusting lappets is explaioed on pagc 25,
^off "^t clutch. A few sirokei of'rhe gease errn at F aFig. ll)
- - will ensure free movemeDt oI lhe cootrol a!m. There
chould be å slight amount of play in the clutch cotrtrol
arm on the gearbox--or a short length of free cable at the
hatrdlebar lever end. If the play be.omes exccssive diffi-
culty will be experienced ir changing gear, as the clutch
msy not fully disengage, in which ca,se the control arm
should be adjusted as explained on page 28.
ChrlDs. Check that th€.e is not morc than half-an-inch
up-and-down movem€nt at the centre of the paimary
chain and not morc than thr€e-ouarlers of aD inoh in the
cåsc of the rear chain fitted to Comp. or plunger frames
(onc-and-a-quarter inch fot swioging atu .nodels). If
cxctssivc ldjust as €xplained on pages 30 to 32.
EVERY 2.OOO MILT^S.
Oll Tank. Drrin out the old oil (preferably after a run
whilc thc cnginc is still warm), wash out with flushing oil
or thin mrchinc oil-NOT paramn or petrol-and refill
with new oil, Wash tiltcr thoroughly in petrol or parafrn
and makc surc that it is absolut€ly dry before replacing.
Oll PumD Filt€r. Removc the platc below the oil pump
and wash the gauze filter ilt paraffin; dry and r€plac€.
Dyoåmo and Magneto. See Elechical Section pages 63, 64.
Mtgdyoo Fixiq. Slacken of the magdyno strap and
pull the magdyno towards the nearside of the machine-
i.e., away ftom the timing cov€r, This ensures that the
oil seal is maintfied betw€en the magdyno pinion and
the felt washer. Holding the unit irl this position re-tighten
the magdyno strap bolt,
Primåry Chsln Oilbath, Drain, and rcplenish with new
oil to level of plug at side of case behind brake pedal.
On Comp. models and machines fitted with swinging arm
suspension thc oilbath is sliShtly larger. Two red paintc(l
covcr fixing scrcws (,4 trnd A, Ijig. 3) llrc provi(tcd 'Ihcy
It
arc tbe level indicaior and drain screws resf,€ctivcly.
The oil level should be determined with the machite otr
level ground ofl thc stand. Do not fill above this level or
clutch slip may occur.
Brake Fulcrum Pin. (7'brakes ody). Check tightness of
lockinS out oa brake cover plate.
Centrtl Stand Fulcrum. Give orle or two shokes of thc
8I€aSe $rn.
Gcsibot. Remove drain plug at bottom of gearbox snd
drain out old oil, Wash out gqrbox with flushing oil ard
rrfiI with new oil to level of filler plug. Ol swinging arm
machines the gearbox is fitted wilh a level plug (see K,
Fig. 13),
Chains. Remove both ohains, clean thoroughly in petrol
or paraffio, and then gently warm in a mixture of Srsso
aod graphite. Wh€o cool, wipc off the excess greasc,
clean thc splockets and replac€ the chain. Remembct
that when replacing a chain fitted with a delachablg
connecting link that the spring fasteDer mult alwayr ba
frtted with the clos€d end facinS the forward dirEction
of travcl (i.c., on lhe top run) of tbc cbain.
Flg. l. Prirnary Chain Oilbath (Comp. and Swinglng
Atn nodels\
lr
,l
I
il
il
lr
i
i
l,-

ADJUSTMENTS CALLED FOR IN TIIE
PREVIOUS SECTION
F.ont H$b. This is fitted with bau journal beaxings and
adjustment is not necessary. The only attention required
is periodical grease gun lubrication as described on page 17.
Removal ofFront Wheel ( ? in. Brake only). To iemove the
front wheel from the forks, detach the brake cable, and
then slacken the pinch bolt ,4 (Fig. 4) at the front of tle
nea$ide fork end. Insefi a tommy bar in the hole in the
spindle end.a and unscrew. Note that the spindle has a
left hand thread and unscrews when tumed in å clockwise
direction. It can then be withdrawn, and by sliding bush C
in the fork end outwards to its fullest extent, the whe€l
llill drop out.
Following the rcplacement of the spindle and before
pinch bolt ,{ is tightened, the forks must be depressed
Fir!. 4. Rcnoral offront nheel
20 I
sharply once or twice to enable the nearside fork end to
alien itself on the bush C. If this p.ecaution is not
obsewed, the fork leg may be clipped out ofposition and
will not function cofiectly. Do not forget to tighten the
bolt .4. (For removal of lront wheel with 8 in. brake s€e
page 60 iD Cold Star Secrion.)
Fo*s. There is no adjustment provided for the telescopic
forks and the only maintenance likely to be requircd,
apart from the routine check on the tightness of nuts and
bolts, is attention to the oil level in the hydraulic damping
system. If, after considerable mileåge, the forks appear
to develop excessive up and down movement, it may
be an indication that the oil supply rcquircs replenishing.
To do this remove the large hexagor headed cap A (Fig. 5)
at the top of each fork leg and also the small drain plugs
shown in Fig. 6. After all the oil has drained out of each
Fig.5. Front fork and steering head

/?Zc'c.? o/JL i votle 64 x
leg, replace the diain plugs and refll to thc coræct lcvcl.
B3r, 833, 5 fl. oz. (142 c.c.) of oil in ea.i leg. 832, 834
Competition and cold Star, 7l fl. oz- (213 c.c.) ia each
leg. Or no account must the fork legs be flIed dght trp
to tbe top or the forks rill be unrble to fuction. The correct
grades of oil for both twes of t€lesclpic forks arc given
in the lubrication chart on page 36.
Remoyål of the Rear lllr€el (Plunger SFing Frame, Fig. 7),
The rear whe€l is of the quickly-detachable type. As it
is fitted wilh ball journal bearings adjustment is Dot
necessary. To remove the wheel place the machite on
its staDd. On fiachines fitted with touring mudguaids
filst slacken the nuts at the slotted fixing stay ends
discomect the rear lamp by means of the special coupling,
when the .ear portion of the guard can be lifted upwards
on its hinge clear of the wheel.
To temove the wheel it is necessary first to hold thc
outer nut ,4 on the left hand end of the wheel spindle with
a suitable spanner when the spindle itself may be u!-
screwed f.om the right hand side with the aid ofa tommy-
bar at C. Removal of the distance piece betw€eD the hub
and the wheel bracket allows thc wheel to be withdrawd
sidcways frod its driving splines, when it can be taken
out rearwards.
Rear Wheel Remoyal (Comp. and Swinging Arm models).
This is quickly detåchable, is 6tted with ball journal
bearings and thereforc no adjustrnert is oeccssary. To
remove the wheel, place the machirc oD iB stan4 itrs€rt a
to[uny bar in the spindle €nd 4 Fig. 8, aDd unscrew itr ao
anti-clockwise directioo until it caD be withdrasn. The
distance piec.e -E can then be removed and the wheel
withdrawn sideways from its driviDg splin6, when it cao
b€ taken out dowtrwards and rearwards.
Note. The lrrge nut (8, Fig. 7, plunger frrmel (4,
Fig, 8- Srltrgirg Arm Frame) on the lefa batrd end of tåe
wheel spinrlle retains tåe whole of lho brakc assembly åtrd
should trot be disffied for purpoae of rheel removal
Wheel AligrDe . Make su!€ that the wheel is hard up
against the adjusting stops whetr checkiDg, atrd also that
the adjustrneDt is €qual on both sides of the wheel (io the
casc of spring frame models) so that the latter is itr colr€ct
Fig. 7. Rear Wheel (Plunger Spring Frame)
I

aligndcnt in the frame. Adjustment is prcferably carried
out with the aid of a shaight edge placed ålong the sides
of the wheels, In the case of machines fitted with tyres of
thJ same size on fiont and rear wheels, the straight edge
should touch both sides ofboth tyres. Ifthe front tyre is;f
a smaller section than the rear, due allowance will have to
be made for this.
Steering Head. It is first necessary to raise the frcnt wheel
clear of the ground-a block or box under the crarkcase
is the best method. Unsøew the damDer knob- with
stem and the steering head locknut B (Fig. 5). Siacken
the head clip bolt C.
Fiq.8. Reor Wheel (Swihging Am Frane)
uI --r-
Tlghten tie adjusting sleeve E until the slackness i.e, up
atrd down play has been taken up. Do not overtighteo or
stcering will be stiff and the ball {aces may be damaged.
After adjushnent is completed tighten the clip bolt C,
atrd the steedog head locknut B.
Exhaust Valre Llfter. The exhaust valve lifter oam must
always be well clear of the rocker arm (see Fig. 9), other-
wise the engine will be noisy and the tappet clearanccs
seriously affected, Failure to check that there is cleamnce
at this point may result in a badly bumt exlaust valve.
Adjustment is usually caried out by means of the cable
adjuster sdewed into the exhaust rocker box cover, but
the actuating arm can be r€moved and ftset to arny
position on its serated shaft,
Tappet Adiustment. Beforc any attempt is made to adjust
valve clearances, verify that the exhaust valve lifter is
corle4tly adjusted as explained in the previous pangmph.
EII.IAUST VÅIVE
Fig.g. fuhaust rølve lifter adjustment
(Valve stem cåp$ are fftted to B31 only)
I
I
I
l

To check and adjust valve clearanoes, it i! host eslential,
owing to the special design of the cam form (sc€ Fig. lO),
to adhcle to the following procedure. Romove thc
inspection cover at the top and the tappet cover .t tho
base of the pushrod cover tubo.
I Rotate enginc forward until rbc idet vslve bas just
I closed (i.e., tbe tappet is just frec to rotate). Thir is tha
I corrcct position for che.kiDg and adjusting thc exhrurt
' valve clearance.
I Tum cngine forward agBin until the exhausl valve
I clearance is just tak€n up, but beforc valve actuslly
I slarts to lift. This is tbe cor.ect positjon for checkinS
J and adjusting the inlet valvc clearance.
' Both htet and exhaust cleamnces are ,003 ltr. exceDt
ln the cåse oI (iotc 5tius. (tee page Ju.,
It is advisable, b€fore inscrtirg a feeler gaugo between
the lower push rod €nd and tappet end to ch€ck thc
clearance on the ongine, to lift the push rod with the
fngers, otheipise the weight of the rod may prevent thc
gauge being inserted corectly, or may give a falso tåppet
sctuDg.
Thc actual adjultment (excepting Gold Star cngiDes otr
atrd afte! engine truDbcr with prefii 'CB'. S€€ page 50) is
carriod out a8 follows. Hold the tappet head ,4 with a
spantrer, and rclease the locknut B (Fig. 1O). Apply a
spatrocr to tha ats oo the trppet stem, holdiog the latt€.
statioDary aDd at the lamc ti[re adjust the head I up or
dowD as requfuid. When correct clearance is obtained,
the locknut , must be tighteDed against the tappet heåd.
Clearances should agaitr be checked before replacing the
inspeatioo and tlpp€t cavers.
If thcse instrugtions are disregarded, and the tappets
are adjusted at aDy other positions of the ca$s, insteåd
of at tle precise positions just described, there will be a
rfuk of dificlrlt startiag, adrc$e perfomatrce, ov€.-
heating, and valv€ buming.
Tappet adjustment should always b€ cå.ried out with
thc eagine dead cold, sud the clearances r€coomended
above rgarded a! a miniqum, ospacis[y h tho oaro of
thc cxhaust valvc.
I
ro .008iD"
FALL FINISHES.
^ccvnrltl,? BE
r^ia om.E cERtar! tE^t clf rosrtlox!
^E coRFlct wHrN rDtus
B.S.^. CAM.
l
Fig. 10. Tappet adjustmen
a1

,,,, ,. I*ll:".Tqi"g. rt u-a rare ffiilcc ror-thc masneto
' .j : prnron to slacken _98 gnd df{ilcb the igritiotr seuins-
"ååd.d,ii,*",^gTm l: ;:rmfl ,:"i rr,. .,'å"i?
It is, however, advisable to check over the timing after
c4rrymg out-any adjustment ro the magneto cåntact
polDls, as- a sttght variarion of the points tends to advaDce
or .retard the trming. (Opening the points advances
umtng, ctostng tåem retards !imiDg.)
t/ -I.f lhe timing requires re-sefting, first che.k that fie
,, ruuy-open gap at ttre poiD6 iq between .Ol0 in. aDd .Ol2 in.
, ln:l re.gpÆ,ih9 rimins q{er: al,.d in S-doineTå[Eh
not.ro dåyrlåEE thesmall frdløe ff fie riming cover which
reeos olt_to the hollow crankshaft. It is advisable to leave
:T",,b*.S sqews in position (half unscrewed aod spaced
equa y rouod tle cover) while the cover joint is brokeD.
With the cove! r€moved, take of the nut locking the
111ETt9 pinign on !!s-shaft,_aod with the aid of a maioeio
pln.lon extractor withdraw tbe pinion. (Note:_The Iatter
ts.altacned -to a.taprr€d shafr and can only be releascd
wfin salety by ustng the proper extraqor.)
. To reset the timing, tum the eDgiae forward utrtil the
pNlon reaches top dead centle on tlero/trpression stroke.
Now turb the engine bact until the fi3(6f, ha. O".""na.J
ft in. (BjJ, . in.). This operat ion is siinptined ir top iåil!
engaged aDd the rear wheel tumed backward.. (poi Cofa
Star models see.page 53.) Turn rhe contacl bleaker in irs
du€ctton of_t^otalion until the points are just open (not
more rban .00.2 io.),_wiri_ the ignition tevir in ihe fu y
advanc€d -positiotr. Lightly tap rhe rnagneto pinion on
ro tls snaltr ltgh-ten t]le nut, and carefully check figures
and posriions. If setring is correct, finally tighre; the
ma€nero ptnlon Dut. t t is ftost impon4nt that the ignil ion
scttlng is accurate. Too much or too ti le advan;e will
rcsult in. highcr running temperaturcs -a auv *ua"
ptslon seizure. (See also Magdyno Fixing page tg.) ,/
('hrtch. Thc mflin clurch adjusrment is totally enclosed'
l|t thc gcitrbox r,Lrrcr cover, and is exposed when the 6llcr
cnn rs r€nx)vc(|,
, The adjustitrg scrcw 4 Fig. t t, is locked in posirioo by
tle nut,{.. For Comp. and swingi-o8 arm modils see Fig,
13, /l and C respectively, aod after releasing the latre;,
adJust the screw so that there is a little clearance between
the. ball atrd the clutch push rod, Then re-tiShten the
locknut and replace the filler plug.
Fig.ll. Clutch and lront chain adjustmenl
Fu her adjustment is prcvided by the knurled thumb nut
C (-E oncorb_p. and Swinging ArD), on top of the g€arbol
KememDer, tlowever, lbat some free movement itr the
control arm is necessary, as if rbe adjustmen( is too close
ruere wl be conslant pressure on the clutch, with con_
sequrnl wear aqd loss ofefficiency, (For Cold Star RaciDg
see Handlebar levers, paSe 57.)
C'lutch Sprfug Pressure. After a considerable mileage it
may be desirable to iacre€se tbe spring pressurel a little.
Firsl drain lbe Pdmary chain oilbath as exDlain€d oD
page 18 aDd remove tbe outer balf of tte oilbath thus
exposiDg tlle clutch. It wil be seetr that the clutch Dlates
are compressed togetber by springs, the pressure of which
is coolrolled by fte nu$ , (Fig. 12) aDd locktruls,4. To
rncrease -the spring pressurc, release thc locknuts a!d.
tiShtcn the nuts B slightly. It is important that each ol
29
I
t.|
tl
|l
t1
fl
il
tl

I
the six adjusting nuts are tighteDed equally 10 €Dsuro cveD
pr€ssure, otherwise the plates will slide uDeveDly aod clutch
drag will result. After the ådjustmetrt is completed, depr€ss
the clutch lever and spin the clutch by operating the
kickst4rter, when the outer plate should be se€n to tevolve
parallel with the other plates. If flot, adjust individual
r sDrinss until.the Dlates are true.
) rtr:&frmy Cfdl#(it*g.r modelsJ. The chajn is adjusted
by slackening the two large nuts under the gearbox, one
on the left hand end of the adjuster and one on the right-
hand side (see r, Fig, 1l), and screwing up the adjuster
nut E This draws the gearbox rearwards, tightening the
chain. Donl forgel to tighten.ngil.P *ien.correct
lension is obtained, \r hich should ,ilfow half-an-inqh upt,r--
and down movement at the tisltest polii6fT-e-iIåif,. '- """
Ttr66-iE-at after tighrening chiin. reår chain will need
adjusting. tul '
Flg.12. Clutch spdng adJustment
E:o1'aa tFrnnr 1cdttr a* l/y{ø nixcil:isr't
is adjusted by pivoting the actual gearbox backwards or
forwards about its lower fixing bolt ,4, Fig. 13. This
operation is carried out as follows:-
Slacken the two large nuts ,4 and ,B which lock the gearbox
in position. One of these nuts is immediately under, and
the other vertically above the gea.rbox. The latter t also
holds ihe adjuster in position.
Fig. 13. Clutch and front ehain adjustment (swinging arm
models only)
Release the locknul C on the adjuster and screw the
actual adjuster nut D in a downwards dircotion, this will
draw the gearbox backwards, tightening the chaio. There
shoutd not be less than a total of half-an-inch up and dowtr
movement in the centle at the tightest point of the chain'
Finally, retighten the adjuster locknut C and the two
large gearbox fixing truts ,4 and -&. Note that aJter tight€n-
ing this chain the rea. ch?lin will need checkiDg.
Rea. Chaitr Adiustment (plunget spring frame). Fig. 7).
ilold tbe hexagon I with a suitable spaDner and uoscrew
PriEary Chain (with Swinging Arm modeis), The chain

thc spindle slightly by means ofa to@ny bar at C. Slacken
ofr the hexagoD B on the left-hand side of the hub dren
screw the adjusters D in or out as the case may be, until
the chain tensioD is correct, with not less than i in. total
up-and-do\rn movement, at the ceDtre of the bottom run
of the chain *itlr the machine oD its central stand. so
that the rear wheel is in its lowest positiotr.
Resr Chain Adiurboe[t (Comp. and Swinging Arm
models). Uascrqw the spindle 4 Fig. 8, slightiy with a
tomDy bar then slacken ofr the hexagon ,4 oD the left
hand side of the hub, Release the locknuts C and søew
the adjusters D in or out as the case may be, until the
chain ten3ion is correct, with not less than I I in. (Comp.
l in.) total up-and-down movemeDt at the centre of the
bottom ru! of ihe chaio.
To allow for any variation in chain tensioD the wheel
should be rotated by hand until the tightest pointis fouad,
with the wheel in its lowest positiotr.
Front Brake Adiustmeot The lenSth ofthe brake cable can
be altered at its lower end by means of a knurled thumbnut
on the cable stop, (For Gold Står Racing, see HaDdlebar
lcvers, page 57.)
Resr Brake Adiustment Finger adjustment is provided at
the end of brake rod.
Do not set the blakes too closely, since, particularly in
tho case of the front brake, its action may be too power{ul.
Any friction between lining and drum will obviously
impair the macbine's pedomanc€. In addition, if carded
to extremes, the heat may melt the grease in the hubs and
this may find its way to the brak€ linhgs. (For lub cation
see page 16.)
Centralising (7in. Brakes only). Slacken the nut on thc
brake cover plate, thus loosening the fulcrum pin in its
slotted hole. Apply brake, when fulcrum pin will auto-
matically c€ntralise the assembly, and keeping lhc brake
on, finally lock up the nut. (See also page 19.)
Brrkc Crm Spindlcs. Thesc arc lubricated with oil scc
fugc lli.
32
Sprking Plugs. The spdking plug is of Sleat importance
in satisfactory engine perfomalce, and every care should
be taken to fit the correct type when replacements arc
necessary. There is little 1o be gained by experimenting
with different plugs as the make and twe fitted by u$ as
official factory equipment is best suited to the rcquire-
ments of the motor. This is Champion Type No. L10S
(competition models NA8. Gold Stars, see page 56).
Fis.14, The spa*ing plug
Remove each sparking plug every 1,000 miles (1,500
km.) or so for idspection. lf the carbu.ation system is in
correct adjustment the sparking plug points should
Emain clean ahnost indefinitely. An ovel- ch mixtwe
fiom the carburetter will, however, cause the fomation
of a sooty deposit on the points, and, later, on the plug
end face (!s upper view, Fig. 14). If thereforc such a
deposit is found, clean it off carefully and check your
carbuletter.
The continued use of leaded fuel may also evettually
produce a deposit on the plug-this time of a geyish
colouf.
3l

- A liSht deposit due to any of these causcs can easily be
cleaned off, but if it is allowed to accumulate, particularly
inside the body, the ptug may spark internally with an
adverse effect on engine perfoftnanc€-if, indeed, ir does
not stop the engine altogether. The plugs should be
cleaned and resled at regllar interuals, and it is suggested
rnar rhrs servtce be pertbrmed at your garage on a special
'Air Blast'service unit. lfeventually the cleaning process
Ialls to restore lhe plug !o ils original condition of
emcieDcy, it should be replaced by a new one.
Fig. 15. Sc ing the plug pornrs
. When lnsp€oting a plug. also check the gap between
the poinrs. This shoutd be .018-.020 in. (.45_.50 mm.)
and adjustment should be made by bending the side wiri
Gee Fig. l5). Neyer åtfempt to moye Oc centre electuode,
and it is alwaJs ad'"isable to use lhe special plug gap rooi
lrusrmteo. obtalnatrle at 2/_ trom any Champion plug
stockist or from lhe Champion Sparking plug Co. Ltd.
Felrham, Middlesex. Feelei gauges are atrached to vcrify
conect gap.
When refittinS a plug, make slrle that the copper warsher
0;t:,
34 35
is not defective in any way. If it has become worn and
flattened, fit a new one to €nsure a gastightjoillt.
Screw the plug down by hand as far as possiblq then
use a spanner for tightening only. Always use a tubular
box spanner to avoid possible fiact$e of the insulator
and do notin any circumstances use an adjustable spanner
Paint splashes, accumulation of grime and dust- etc.,
on tle top half of the insulator are often responsible for
poor plug pcrformance. Plugs should be wiped fre4uenlly
with a clean rag.
Air Cleån€r (when fitted to Comp. or Plunger models).
This being of the oil dip typc, needs to be dismantled and
cleaned periodically. The filter ele&ent should be washed
thoroughly in petrol, allowed to dry, and then submerged
in light engine oil for a few minutes. Then take out, allow
the surplus oil to drain of and .eassemble.
Atu Cleåner (fitted to swinging arrn machhes). This is
in front of lhc battery cårrier, and is coupled to the
carburetter by means of a rubber elbow. The filter
element must be remov€d periodicålly when it should be
washed thoroughly in petrol, dried, and then submerged
in thin oil (SAE20) for a few minutes. Theo take out,
allow the surplus oil to drain ofr and reassemble. This
operation is carried out as follows:-
The Cleaner cover is attached by two sqews in elongated
slots, the lower to the frame member below the seat and
the other to the battery strap. The rubber connection to
the carburetter should be left in position on the carburetter
inlet stub and slipped off the cleaner cover.
The ltlter is held in the cleaDer cover by a wire circlip.
Note: The domed surface of the p€rforated retaining disc
must be replaced upwards.
Cylinrler Head. After the machine has covered its 6rst
250 miles from new or after decarbonising, check the
tightness of the cylinder head bolts. If they need to be
tightened work in diagonal order to ensure that the head
is tightened evenly, otherwise distortion may result.

14 1lL 3 1lt 2 't1lL
KEY LIJBRICAT'ION POINTS
(L irdioto lelt Land side, romaindor rislt haDd or both .ides.)
RECOMMENDED LTJBRICANTS
oLs
Ensid., Gc!!bor, Front Fork! coMP. &
O. STAR
FRONT
FORKS
ONLY CREASB
Brdd
Mobiloil DNo. 2
Shcll xlm-50 xl0G30 xl00-20
clltrcl XL Hcavy
E!!o 50 30 20
B,P. sr.E
50 SAE
30 SAE 20 Eneg.as.
FOR OIaERSEAS. Ræomcndalions as above if obiaio.bt..
If rot th. followins ru|. shoutd tE ob*ned:- Th. Hicb6.
tbc Tedpcråturo !h€ Higbcr is rhc S.A.E. Numbe. rcquir.d.
(Ansioc G.ebor) SuDmcr 50
(md F.ont Forks) Wi.t . S.A.E.40-20
Front Fork3 (Comp. and G. Star only) S.A.E, 20 Gæ paeo 2l)
36
ft'EETLY LI'DRICATION
GREASE OIL
t2 Staing Udd L7 Oil Tu* l5
t0 Såddlo Noi. Eolr l7 !t7
l3 t7 7 B!åkG P.dal t7
E17
t7
SPECIAL NOTES
P-'Finc Enain. Prcls. v.lvo ål 1,000 miLs. (S.€'A'ras! IJ)
r &d 2. Cl.a. Oil Tak ad C!ekø3. Filt rr at
2,000 Dil.s.
I !d 3. Drain aad Refill Oil Tlnk aDd G.a$ox at
2000 milcs.
5. Ct@k Frcnt Fork Oil Lå,.1rt 10,000 mil.8.
!
LI]BRICATION EVERY I.OO|) MILES
R.f, GREASE Rc!, OIL
ll Hubs t7 6(7in. Bralc) c@
Soindles IE
l8
6(8 lr. F. B.rkc) cm l8
LUARICATION EI1ERY 2.()OO MILES
GRXASE oIL
t4 C@lral Sratrd t8 tOil TMk 1E
3l9
4Oilbath IE
9l8
Rcar ChaE l8