BSA 1971 B25SS Gold Star Instruction manual

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Worl<shop
B25SS
B25T
B50SS
B5OT
BSOMX
..
Gold Star, :*
Victor
Gold Sta,r
Printed in EnSland at
B.S.A. Press
May,19t-1
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Please Note !
Replacement pants or accessories must be of
B.S.A. origin or as approved by B.S.A. Motor
Cycles Ltd.
In this respect your attention is drawn to the
Tcrrms and Conditions of B.S.A. Guarantee.
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lntrod uction
This manual has been compiled to provide comprelrensive service information for the B.S.A. orvner
and lor the workshop fittel rvishing to carry oLrt either basic maintenance or major repair work. It is written
in great detail. but because of the specialised skills and equipnlent required to carry oLrt some of the rvork
described. the irrexperienced owner is strongly advised to consult his dealer whenever he is irr doubt as to
his own ability to calry oLlt a satisfactory job.
The manual is divided into sections dealirrg rvith tlle major assemblies and these are sub-divided into
the individual operations reqr"rired for maintenance and repair. It is hoped that by using this arrangement.
the manual \yill be lound most uselul as a quick rvork of relerence even to the skilled mechanic.
All information and data given in this nlanual is correct at the time of publication but because of our
policy of constant development. changes in specification are inevitable. Anyone finding this manual to be
at variance with the niachine in his possession is advised to contact the Service Department. where up-to-date
intbrmation will be qLrickly provided.
ENGINE AND FRAME NUMBERS
Both engine and frame nunlbers. together with prefix and sr,rffix letters, must be quoted in full on any
correspondence relating to the machine or on any enquiry re_earding this manual, to either the dealer or the
Service DepartInent.
The engine number ("A") is stamped on the left-hand side ol the crankcase immediately below the
cylinder base. The frame nunlber ("8") is stamped on the prop-stand lug, or. on later models, on the left
side of the steerins head-
N
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F00t0t B25T
FrG. l, Engine and frane nunbers, Page 9
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Factory Service Arrangements
(UNITED KINGDOM)
REPLACEMENT PARTS
Replacement parts are distributed through a national network of B.S.A. dealers, each of whom holds
a stock of fast moving pafis. These dealers have been selected for appointment as specialist replacement
part stockists and each holds a cornprehensive stock of replacement parts.
A complete list of appointed stockists is printed at the end ol this manual, and also in every parts list.
GUARANTEE CLAIMS
In the interests of all concenred jt is best that any owner of a new motor-cycle wishing to clainr
assistance under g[arantee should do so through the dealer from whom his machine was purchased. All
B.S.A. dealers are faniliar with the procedure designed to give quick service to any owner of a B.S.A.
motor-cycle who may find himself in difficLr1t1,.
REPAIRS
Most appointed B.S.A. dealers are able to carry out maior repair work, and owners are asked to make
all repair arrangements through their choseu dealer.
ln the great nrajority of cases local repail will be possible and this will avoid the expense, inconvenience,
and possibility of the machine being damaged in transit to or from the works.
Should your dealer decide that Service Department attention is required he will know how to nake
suitable arrangements with the factory. It is important to remember that a machine cannot be accepted at the
works without prior appointment. Appointments may be made either by Ietter or telephone.
TECHNICAL ADVICE
B.S.A. Service Department staff are experienced in dealing with technical problems of all kinds and
will be pleased to help in the event of dimculty. The corect address ofthe Service Department is as follows:-
B.S.A. MOTOR CYCLES LIMITED.
SERVICE DEPARTMENT,
ARMOURY ROAD,
BIRMINGHAM, BII 2PX.
Telephone : 021-'772 2381,
WORLD SERVICE ARRANGEMENTS
In most markets of the world, B.S.A. have an appointed distributor to whom all service enquiries
should be addressed.
These distributors are listed at the back of this manual, and also in all parts lists.
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PROPRIETARY PARTS
Equipment not of our ntanulactLlre which is iitted to oLlr motor-cycles is of the highest quality. but
guaranteed separately by the manufacturer concerned. Any complaint or repair should be addressed to
the manufacturer or his accredited agent who will give every possible assistance.
CARBURETTERS Anal Lirnited.
Holdford Road,
Witto|r,
BIRMINGHAM 6.
Renolds Chains Limited,
Renold House,
Wythenshawe,
M ANCHESTE R.
Joseph Lucas Limited,
Gt. Hampton Street,
BIRMINGHAM I8.
Girling Limited.
Birmingham Road,
WEST BROMWICH,
Staffordshire.
Champion Sparking Plug Co. Ltd.,
FELTHAM.
Middlesex.
Smith's Motor Accessories Limited,
Cricklewood Works,
LONDON N.W.2.
Dunlop Company Limited,
Fort Dunlop,
BIRMINGHAM 24.
CH A INS
ELECTRTCAL EQ UIPM ENT
REAR DAMPERS
SPARK I NG PLUGS
SPEEDOMETERS
TYRES
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U.S.A. SERVICE ARRANGEMENTS
REPLACEMENT PARTS
Replacenent pqtls ore lr.tilclble tltrcugh a nenorlr ol B.S.A. dealers <orering the etltite Li ited States,
Tltese deqlers qre listed uuler " lllotorq,cles" in the )ello| l,qges ol lour telephone diectotr-. All rcquests Jb,.
Ports niLtst be uttde through.fiqnchisecl B.S.A. tlealers: they are not solcl clireo to orners hl the tvolAdot.l
brqnches.
GUARANTEE CLAIMS
rlutst do so through lhe dealer.front vhon his macltine tas purchosecl.
REPAIRS
B.S.A. de7lers ore ctpable o.l serficing {tnd rcpdiring B.S.A. tllotot-()'(l€sl. crsk tour dealer to help vhen
repairs are needecl.
Labout' tine vill be greatl retlnced if proptietar), at ti(les, suth os legshields, crosh bars, r'orriers or fibre-
glass.foirings ore remotetl beJ-tre handing the nqchine ot'er.for repair. Accessorie.t su(h as nirrors or batlges
shotid eltto.t's be rcntoled beJbre entrLtstittg a tl1a(hine Io {ttt indepentlent torrier.
TECHNICAL ADVICE
The B.S.A, Service Depqrtment stof qt the lvo U.S.A..fa(tot! brunches are exteriencecl in tlealing u.itft
technical questions of ctll kinds cutd v'ill be pleasetl to help itt the erent of dfficultl'.
The.factory hronch cultlresses ore shotcn belo\':,
EASTERN:. The Birnringhanr Snall Arms Company Incorporated.
B.S.A. Sales Division,
P.O. Box 6790,
Towson,
Baltimore,
Maryland 21204.
The Birmingham Small Arns Company Incorporated,
B.S.A. Sales Division.
P.O. Box 337,
Dualte.
California 91010.
WESTERN:
ht all contfittuticcttions tlle engil1e andftcune nwtbers v,ith pref x and suJfx Ietters ontl fgures nusl be quotel
os tell as the year and notlel of the motot-c):tle in tluection.
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B.S.A. DEALER PRE-DELIVERI' SERVICE
The follouing lasks musl be conpleted belore making dclivcly ol a nerv B.S.A. nrotor ctcle: -
(I) CHECK CLEANLINESS AND CORRECT SPARK PLUG GAP.
(2) CHECK AND ADJUST TYRE PRESSURES,
(3) CHECK ALL EXTERNAL NUTS AND BOLTS FOR SECURITY.
{4) FILL AND CHARGE BATTERY IN ACCORDANCE WITH FOLLOWING INSTR UC-
TIONS
(5) CHECK ALL LIGHTS AND HORN.
(,') CHECK AND CORRECT IF NECESSARY ALL OIL LEVELS.
(7) CHECK. ADJUST AND LUBRICATE CONTROLS AND CABLES.
(8) APPLY GREASE AT ALL GREASE POINTS.
(9) TEST MACHINE ON ROAD TO ENSURE FULL ROAD WORTHINESS.
(IO) REPORT ANY PROBLEMS TO B.S.A. SERVICE DEPARTI\4ENT BEFORE DELIVERY.
(II) SIGN AND RETURN PRE-DELIVERY CHECK CARD.
Fajlure to carry out these checks or to sign and retLlrn tl're pre-delirerl check card rvill nullily arrange-
ments for the pa)'ment of guarantee labour costs.
BATTERY
The battery is supplied in a dry-charged corrditiorr and nlust rot be 6lled unless it is krrorvn that the machine
is to be sold rvithin a ferv days.
To fill and charge the battery-
All plates in the battery have been ch;.rged lully and dried completely by special proces.. The tape across the
ver]t holes prs\ents the ingress of moistule ol air and insrrres perlect condition ofthe plates durins transporta-
lion and.tora:"e. 1hi' rape nro.r onl) be rentored inrnedntelr before the batterr j. brori3ht into 'errice.
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Dilure sulphulic solutiorr S.G. 1.260 is be prepared by slowly pouling one part of concentrated sulphulic
ucid jnto three parts of distilled water (by volune) ol olS.G. 1.210 by adding one part of concentrated
sr.rlphLrric acid to tbur paris ol distilled water (b,\, volulne). It is ftlost important to add acid to nater, not
waler to acid due to the violence of the chetlical reactiorr involved.
A glass. ealthenware or lead ressel should be used and the nixtLlre well stirfed. Allo\\'to cool to the
temperatu[e of the surroundil']g atnosphete belote use.
Important:-With dry-charged batteries the filling of each cell with acid nust be completed in one
operation and levels restored after standing by syphoning off excess acid.
Fill each cell rrith dilute sulphuric acid to the "maximum" line at one operation. The temperature of the
acid and battery must be betrveeu 60'F. (15 5'C.) and 80'F. (27'C.) (see chart).
TEMPERATE
Clinates ordinalily'
belorv 90'F. (32'C. )
shade tenlperatule
TROPICA L
Climates frequentl),
above 90'F'(32'C.)
shade tell1perature
Specific grar'ity fbr filling new cells r.260
(at 60'F.. 15.5'C.) I 210 (at 60'F.. 1i. 5'C.)
Specific gr-avity at completion of charge to be
adjusted if necessary. to be between 1 220 and 1 300
(at 60'F.. 15.5'C.) I 2l0 and I 230
(at 60'F.. 15.5'C.)
(1) Batteries rvhich have been stoled at a lower ienperatule than 60'F. (15 5'C.) should have their tem-
perature raised belore filling by allowing the battery to siand in a warm room until it attains room
tenperature.
(2) Batteries used under these conditions are up to 90 per cent charged. but if time pernrits a freshening charge
of four hours at l'0 ampere is beneficial. Il the acid level rises alter the freshenin-s charge restore the
correct level by syphoning off excess acid.
of four hours at the normal recharge rate r,,ould be beneficial. If the acid level rises after this freshening
charge restore levels by syphoning off excess acid.
Important:-On no account should the battery be topped-up to the separator guard, but only to the
"maximum" line.
Paee 14
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CONTENTS
CENERAL D,A.TA
LUBRICATION
ENGINE
CARBURETTER
CHAINS
TORQUE WRENCH
SERVICE TOOLS
USEFUL TABLES
FRAME AND FITTINGS
FRONT FORKS
WHEELS, BRAKES AND TYRES
ELECTRICAL EQUIPMENT
SETTINGS
Se(tiot1
GD
A
B
c
D
E
F
c
H
J
K
L
Page
Ito13
l to 11
lto4l
lto 8
Ito12
Ito 8
lto14
1to17
Ito ,l
7to 2
I to 10
ltol0
Page 15
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825/850 GENERAL DATA GDI
Because the engine and transmission ol the B25 and the 850 nodels are of different specification. it is
ruecessary to divide data into two sections. one lor each nodel. All othef data is applicable torboth nodels
INDEX
ENGINE AND TRANSMTSSION
Ca lbrrreL Ler
Valre> .. ..
Valr e euides
Valresprirrgs .. ..
\ al\ e I irn ins
Crm)hirlr
Trppels .. . .
Spa rl plug
lgrrition tinring .. ..
Cl linder lread .. ..
Cylinder balrel .. ..
Pi:ton .. . .
Pist on lirrgs
Oil pun rp
Connectirrg rod and crankshaft assembly . .
Clutch .. ..
Cearbox
Ceal latios
Sorocket 'ize. tLeerhl ..
t^hlirrs .. ..
FRAME AND FITTINGS:
Front [olk.'
Swinging arm .. ..
Rear srr:pension rrnits
WHEELS. BRAKES AND TYRES:
Wheels .. ..
Brake" .. ..
Tyres
E LECTR.ICAL TQUIPML\ f ,,
CAPACITIIS
DIMENSIONS ,. ,,
WEIGHTS
GEAR RATIO CALCULATION
825
Poge
.. GD2
,. GD2
.. GD2
,. GD2
.. cD2
,. GD2
.. GD3
.. GD3
.. GD3
-. GD3
.. cD3
.. GD3
.. GD3
.. GD4
. GD4
.. cD4
.. GD4
.. GD5
.. GD5
.. GDs
Bs0
Page
GD5
GD6
CD6
GD6
GD6
GD6
GD3
GD7
GD7
cD7
GD7
GD7
GD7
GD7
GD8
GD8
GD8
GD8
GD9
GD9
825j850
GD9
cbe
GDIO
cD l0
cDll
GDI I
GDII
GDI2
GD I2
GD 13
GDI3
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GDz GENERAL DATA 825/850
CARBURETTER
Type
Main jet
Needle jet
Needle position
Throttle valve ..
Choke diameter
Throttle slide return
B25 ENGINE
Amal Concentric 928120
.. 200
. . .106
.. I
.3i
.. 28 mm.
. . 2.5"
VALVES
Seat angle
Head diameter (inlet)
Head dizrmeter (exhaust)
Sterr diameter (inlet) ..
Stel11 diameter (exhaust)
VALVE GUIDES
Material
Bore diarne(er .. ..
Ou tside diarneter
Length
lnrerferelce fit in head
Counterbore in exhaust guide
VALVE SPRINGS
Free length (inner)
Free length (outer)
Fitted length (inner)
Fitted length (outer)
.3130"
.5010'
.0025"
.326't..12" deep
(64cm.)
135.5 nlm.)
(44 5 mm.)
(32.0 mm.)
(34 8 mm.)
45'
I 450', -1 .455"
| .312' -1.317'
'3095', .3100"
.3090"-.3095"
Hidurel 5
. 3120'
. 5005"
1.844"
.0015"
'323'. -
1 .40',
1 .15',
1 .26',
1 .37',
o
VALVE TIMING
Tappets set to 015" ( 381 mln.)
for checking purposes only:
Inlet opens B.T.D.C.
lnlet closes A.B.D.C.
Exhaust opens B.B.D.C.
Exhaust closes A.T.D.C.
51',
68"
78'
31'
.7480"- .7485',
.345',
.906',
.7492"- .7497',
.908', .909',
CAMSFIAFT
Journal dianeter, left and right
Cam lilt (inletl .. . .
Carn lilt terhrust)
Base circle radiu'
Bush bore dianeter, fitted
Bush outside diameter, Ieft and right hand . .
O.
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825/850 GENERAL DATA GD3
TAPPETS
Stenl diameter . .
Clearance in crankcase .-1735" 3740"
.00r "
SPARK PLUG
Ty pe
Cap settillg
Thread ..
Champion N3
.020" 025"
l4 r'nn. ( 50 65 nrnr. )
IGNITION IMING
Piston position lully advauced B.T.D.C.
Crarrkshaft position fully advanced B.T.D.C.
Cotttact breaker galr .cttirrg . . . .
.342"
37'
0t5"
(8 . 6ll nln. )
( 38 rrrll. )
CYLI\DER HEAD
Inlet port size
Exhausl porl size
Material
CYLINDER BARREL
Bore diameter' (standard)
Oversizes
M aterial
PISTON
Compression ralio
Clearance (top oi skirt)
Clearance (bol1(]m of skirt)
Gudgeon pin hole diameler
Material
PISTON RINGS
Width (top and centre)
Width (scrapers)
Depth (top and centre)
Depth (scraper)
Clearance in groove (all rings)
Fitted gap (all rings) ..
N{aterial (all rings)
I . 125"
1 .25"
Alumiuium allo)' LM4 with integral cast iron
valve seats
67 mm.
'020'and 0'10" ( 5andl0nm.)
Alunrniunr .rllo1 LM4 u ith arr'teniLic irorr
liner
l0 : I (alternative ll 5 : l. Fleetstar onlr-)
'0042'- .0053"
'0025'-- 0028"
'6884" 6886"
Aluminium allov H.G.4l i
. 101" .t07'
.10r" .107"
.06t5'-.0625',
.124" .t25"
.001" - 003"
.009' 0r3"
Cast iron H.G, 22
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GD4 GENERAL DATA 825/850
OIL PUMP
CLUTCH
Type
Number of friction plates
Number of plain plates
Or erall thicLuess of fiiction
Free length of springs
Clr.rtch pushrod length. .
Clutch pushrod dianrerer
Clutch roilers .. ..
GEARBOX
Type
Type
Drive ratio
Non-return valve spring free length ..
Non-return valve spring ball diameter
Pressure release valve blorv-olF pressure
Pressure release valve spring free length
Pump bodl marerial .. ..
CONNECTING ROD AND CRANKSHAFT ASSEMBLY
Connecting rod small erd eye dianeter
Connecting rod big end eye diameter
Connecting rod length between centres
Crankshaft big end journal diameter
Regrind undersize'
Crankshaft diameter (left and right)
Big end journal lunning clearance . .
Crankcase main bearing (roller, Ieft)
Crankcase main bearing (ball, right)
.6890',- .6894'
1 .5630"-1 . 5635 "
5.312'.
) . 437 5', ,t 4380"
'010', 020'. .0-10' ( .25, .50, 76 mn.)
.9841" .9844',
.0005"-.0015"
'875"',..2.0" t .5625" (Hoffniann R325L)
'875":<2.O" ./. '5625" (Hoffmann 325)
M ultiplate with integral cush drile
5
5
'167" ( 4.2 mrn.)
I '66' (42.0 rnrn.)
9 0' (22.9 cm.)
' 187 5'
25 off, .1875" x .1875"
4 speed, constant mesl.r
. 5" >:.. 625' r.8125" (Torrington B108)
30 ;< 60.,: 16 mm. (Hoffmann i30)
. 625"'::. I' 5625''<. 4735" (Hoffmann LS7)
.6245',- 6250',
.1485'.- .7 490'.
.6245' 6250"
.752', - .153',
1 . 179' -1 . r80',
Double gear
1..4
.5"
.25"
80 100 lbs. p.s.i.
| .37"
Cast iron
(12.7 mm.)
(5.6-7 0 kg./sq. cm.)
(34.8 nm.)
Layshaft bearings (needle roller)
Mainshaft bearing (left)
Mainshaft bearing (right)
Layshaft diameter (left and right)
Mainshaft dianeter (left)
Mainshaft diameter (right)
Sleeve pinion inside diameter
Sleeve pinion outside diameter
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