Servicing & Tuning Guide

IMPORTANT: Reod Before

Commencing Work

Theselnstructionsareintendedasågenerålguldetoseru.lngandtuningthetype
HlFcarbLrretterln both sing e and mu ti lnstallatlons. lt sessential, particulary
where veh cles arc equipped and tuned to comply !,vith eng ne ern ssior controL
requlat ons, thatthe c.rburette6 aretuned in accordance wth the veh.le
mänufacturer! t!ning data.

Toach eveth€ best res!ks when tuning, the use of a reliable tachometer, balanc n9
meter and an exhaungas ana yserare required.These instruments are essential
whentuning vehicles equipped to €onform with exhaustemission regulations.

Before lervi.ing or tuning a carb!retter in an endeavour to rectit poor englne

performance, make surethatthe ma adjustment orfau t is notfrom anothersource
by.hecklng thefollowing:

Valve c earance
Spark plug .ondition
Contact breaker (dwe langle)
lgnltontm ng and advance
Presence ofair leaks ntotheinductlon synem

This Kitcontains only Genuine5U Components

Copyriqht O 2009 BFS Tednie I Service! / ALT 91 r 0

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After remövin9 tom theengi.e,rhorouqh ycean iå) Mark the bortom.over p ale and body to
the outide olthe carb!rette6 ensure.ore.t rea*emb y (9), unscrewthe
Srandard su(tion.hambe6.lemovo the p ston rela ninq 5.rew5and remove rhe.ov€r
damper (l)a.d its vJasher (21, ifFtied comp.teändjea nqrng
Un5crewrhe 5u«ion chamber rerainifg 5crews (3) tbl R€move thejet ådl!stin9 s.rew.omp ete
and romoverthe ld€.tity taq.
(d) Llltihe.hambera$emby(4)v€ircå yfromthe Remöverthe jet adrusting ever r€taining s(re!r
body w thou(r r ng rt and5prnq(lr) l
W thdrawthejei complete w th adjusti.g eleri
BaU Bearingsu.tion chambers (ealytype). andd senqaqethe €ver (r2l
Holdlh€ pi5ro.irm y and pulithe su.rior chamber, Remove rhefloät prvot spindte andtibre
tak ng care not to bend rhe drmper rod, !ititthe bearins
reia n€,kfreed from thep io. /od (sa) Femove (fl
(9) Remove th€ need e valve (ls)and uis.rew tl.e
Bällbearingsution.hambe6(lär€rrype),
valveseai lcompetewirhiheilter,typer
Remöverthe p «on dåhpe, Liit the p 5to. and remove
the b€ar nq retaininq clip (5b) (hl Unrrew thejer beari.g ockignutand
wthdrawlhe bearing cöhplete w th irs

5
Nore rhe lo.at on ofthe €fds olrhe fast td e
can rever r€turn sp nq (l7l
Un ockand removerhe cam everrera ning nut

Wth the return spr nq held towards the

.arbureiter body. pr se off rhe.am ever..r
(å) Separaiethe su.tion.hamber, ihe spring and rh. rehove the retur. springr t19l
pistoi asemb y (6) a.d empty tle oil from rhe Unscrewthe nårre, un I rerå i.q !.r:p:a.c
remo!erhecoverplare (20)
(b) Unscrewthe need eSu:de ocl< n9 soew(71
(c) Withdrawihen€ed €,9u deaid spr n9 (8)
 W thdrår, the uane, unit a$embiy a.d emove
ilsqa5ketl:llNote onlater«arterunitsthe
.c!erpateand närter bodyare des gned.oltc
1

Th €.sures greater a..urary ofslarteroperat

5 o.
Examineiheih.olt e sptnd e and its beårinqs .
lne carburett€6 body;cIe.kforany worn part5
,ll W thdraw the vä v€spindleand remove rhe
'orn9 sea and duu.ap (22)
Exåm nethe float needle, seat n9 and 6her
whereftted fordamage, refew f nee$ary.
Exam n€ a rlbberseahand o rnq5forany
damaqe or deter o.ation; re.ew as ne(e$ary
The.over p ale sraling r n9 and staner Or n9

(he.k co.d uon ofallibre washets and

gasketsi re.edasneresary

", .-,|

r06<,, 2
(al Exam nerhe.årburetier body forcra.kJ an<l
daoaqe, and fcr se.u.lry of the b
6
1äl Nore trre o.atronand oadingoltheendsof the
1bl Clean the rnside ofrhe su.t on.hamberand the
throitle lever rerurn spring and rehove the pistonrod gu dewirhfue or meth/ared sprt
ldenatured al.ohoil ä.d w pe dry Abra5ives must
(b) Un o.känd reBove the nlt änd täb washer
rerainrnq ihe throttle le!e6 124)
Gl Exam neihe su.i on (hamberand pisr.. for
kl Remov€rthe throtile lever a.d throttie a(t!ar ns dr6age and s qns ofr.oring
lever(25) Ihese mayvaryqu te.onsiderab yfrom
3
Ball bearinq suction chambe15. Checklhar all the
ld) Remove lhethrotleda( relaini.g s.r.ws (26)
ba sare n th€ pision ballrace (2 rows,6 perrow),
{e1 c osethe throttle and mark the pos rio. olrhe
F tihe p xo. into the suct on.hamber w rhout the
rhrottledB. n re ation to thecarbur€1t€r flan9e.
Donotmarkthedtsc n rhe vt.in ty ofthe overiun danperand 5p. n9, ho d the asrenb y in a hortzonral
posltiof and spi. the p slon.The p non shou d ipin
valve Open the throtr e ånd cärefuiiy wthdraw
freely I lhe slct on chamberwirhout any teidan.y
the n 5.frostheihrorlespnd €raking.are nor
to danaqe rhe ovefi!n valv€ (271
(fl W ridraw the th.ott e spind eand remove t5 4
sea r i23l, noilrg th€ tray (
s lirted t. re atio. to Thefo owlfqum n9.he.kapplies o.lyto standard
.arburetrer body to ensure rhe.otrecr reasemb y su.tlon.håmbeE ä.d need oily be.atr.d out ifthe
.ause oi the carburetrer ma fun.i on which
ne.estaredth€d smant n9 ha3 iotbeen o.ared.
la) Temp.rårl! p u9 thepiston transi€rh. er(l).
lbl Fnthepnonintothe.hambrwthourits
 when ait nq the jet å$emblv to the adrust nq
and rcrew, wilh a largeflatwasher
nlt lever ensurerhat rheiet head moves freelv rn th:
Fir a
under the nut, lnlo one of the sucl on'hambe(
6x n9 ho e!, ponuonr.g the lvasher so that
it
(l) (f) Äfu..hu no fie floatänd a!e
n\ertth-o
overLap5.hamberbore .xhrete;50 s hEd
tha( rhe needk valve
FhedamPeraidwasher (4)
''
th€ snut ponnon bv thewelght ofth€ floatonLv
Checkthåtihe p stro. tfullv home ln tne .hprk rhat th€ oolnttnd caredonrhefloar s
chamber, inled the a$emb Y to a ow the o2inl below the Lele
I0-/'o5mm (o 04 +/_ o
chamberto aallawav !ti1 the piston rhe
'ontå'ts of the noåt porit on bv car€iullv bendrrq
bra$ Pad Che.kthat rhe float Pivots
(f) ahe.krherlme taken ror the.årburetrelro raLL
..ne.tl!åboutlhe sp ndle
thefullextenr ofthe p non iravel. For (sl F.surethatthe need e qu deitred qlv€5 rhe
.arburetie6 38 O mm (1.5 in)to 47 6 mm need € bia5 rn the Gquked d re.tion lelther
(17ls n)bore, the time1å(en shÖu d be
töwar.j throt e d s. or toward a rcleaner) Befo«
tohlEnrno the eta n nq5.rEw .he'l rhåt the
(9) f rherimesa'e-"/c€eded.he't thepnonand (o
n;edlequide 5 n ts.orc.rpoeton 'elåtve
.lrdmberr.r presen(e ofo forei9n måttera'd the. {on face erher fl w ih
rh thebortomoi
dåmaoe. lairerr€che.kL.g thet me isnl oribh w th the
wiihinihese lmits, reievr' the su.ilon
'ot fie; sron on sranded F nons
r-.esson re.e$ed P§to.s
thl Ba hFzr nosu.r on.hamb€E To pre!ent the
ononspn;,r rrom bonq aound up during
xambv rcmp.Gr v Ftrhe prnonandsu'tLon
.hambe;,h$thepnonsprig ro ihe bodv anc
.en.ilmarkthetr.elånve posit ons io ea'her
.ihpr Fit the 5Drlnqro the piston hold the
su.rlon chambor overthe sprlnq åfd
pktor' air
rhp öencil marks änd ow€rlhp.hamber overrt
spnnq and pistoi I 5 ess.ntialthaiinebeärin!
.etention.!ip(earlvtvpe)orthebearing
,Frpniiön.l([! 1åter tvpe)is v ]ified
'o(ect

Reasem bie by rcveEing the pro'edure usedlo

disma.t e the cårbureiter, noliig the fo owingl
(a) Enntrerhatthethrottledu. sirted c
'
rhr N.;th,ottted\.,etanrnqs.redsmu«be!5ed
dhe.rehnnclhedE( Ens!rethaith' throttle
d <iscoire.fv posriÖied and
'lose§cotrectv
beforeuqhteniiqtheretaning5'reN5 Spread
the splir;n.ls ofthe s.rews suiiciendv to

k) i,osito. rhe rhrott e splidle e.d ra siln be ow

th.5Plndle houslnqnanqe
1.ll Thestarter un( valve slitted wlththe
'!i_out
towardstheiop reralnlig screw ho e and its
retd'n nq plate spo\irloneddrhrrheso ed
ilänoet;wårds the throtrle sp ndle Applv a
sme;r oro to narter'o rlnqpriorioa$embv
thesta ershoudtheneitertne'arburetter
body w th ease. f for.e has to be ured thG wl
.!arablv re5!ltln damaqeto lhe O ring
.-:

1 (dl Turn thejei adruni.g nurtcrew B)two tu

down/.lockw se (ea.h.ur5.rew on
(he.kthelhrotrl€ for.otrectoperat on and 5 qn! muhcatburetle4l
1e) lurn thefanid eadllst nq s.r.wanri
U.s.rew th. throttle ådiusilng s.rew 1eå.h 5.red . o.kwise 1€a.h s.rew mu ucarburetreE)!
oi muhl .arburctie6) until t isjun.!ear olrhe it swe . ear ofthe ram. {51
throtr!eleverwrh the throttle . osed, then turn 3
rhe screw.o.[wi5€ ].tiullrurn§(s ng e), on: Refi t the 5ucr on chambera$emblv lf t has been
turn on each (muh <arbul€ltetrr 1ll removed and, u5in9 the 1iiti.9 pi (21, ctie.kthåt1
Ra se (he piston ofeach.alburetterwLth the pBtoniallsneely o.tothe brdq! Noler lba
ftlnq pi. (2lanil che.(lhai tfa sfreevonto teari.g sLclion.hambeE areiiued take care not
n §teleased.lfthepston
the bridge r,hen thep vrind up the I non spr nqwhen.efrtri.g thesu.t
showsanyte.da..ytöstick tlrecarb!retter .hamb.r see r.ä$€mb € se.tion
2
Lftandsuppo the p n.n.lear oithe bridge so
Checkrhe pnton damPer oil evei
that thel€r is v tible;ifth s is nol po$ b e due lo
rhe nsta ed potnoi oflFe carb!retler, remove (a) Standard 5u.uon Chambeu U.s.rewrhe
the su.tion.hambe'a$embY and wlthdraw the damper.lop up with o
Turn ihej€t adju5trnq n!rrrew up'ranu.lockw 5e lp.ef€rabLyS.AE20) untl lheeve s just
!nt thejctu flush wlrhthe br dqeoras h qh as belöwrh€töp ofthe holLow p ston rod, re
posjibew(houtex.e.d nq rhe brldqe he !htill the damper and s.rew the.ap fr rmlv into
Ensu.etharthelel5onmulti carburelletrare n 5!droi .h am ber (6al
the 5äme reiat ve poiit on to the bndge olrhelr
r.§pecl v..arb!r.ttets.
che.kthar ihe s niered need e q! de i flueh w ih
the undeBide fa.e olrhe p 5ton (41
lb) Bällbearingslction.hambe (earlvtvpe)
unscr€w the.apand caref!llv rai5€ the pislo.

ffi
anddamp€rrothetopolthertlave F rhe
r€.es in the damFer retainerdlih oll
(preierably 5.A.E 2o) , owerth€damperunn
rhe .ap conia.ts the 5!.uor (håmbei repeåt thi5
procedure unt I tlre o level srLn! 5lb e at the
bottom ofthe reta n€. re.e*.5.rew the.ap
6rmlyrnto the suct on chambe.lt G €5§entialthat
ihebear ng retaineti5.ordi5pla.ed from ts
positionlnihePisto. rod (6bl (c)
(c) Ballbeårinqsucrion.hambosllalerr/pe)
Unsrew the dåmper cap and wlthdlaw the
damperrop uP w th o (Preferab Y
5.A E 20)to wiih n 6 5mm (0.2s i)ofthe iop of
theho ow piston rod Rentthedamparand

5
G) Vehkeswithemm s.i conlro.Conne.tare able
ra.hometerio the enqine l. å.cordance wlth the
innrumenl mänufa.tureu nstrucuons.
rb) sra the enqine and run iiat a ia31 idle speed unril
taita ns.orma tu.n ngremperålur€ thenrunit 2
for a fu herive m nutes Veh <lۤwith emission control. Using the era!5r!as
(c) lnGa5e lhe engl.e speed to 2,s00 rp m for 30 åna yser che.kthat th€ percentage ao reanlng n
w thln ih€ llm ts glven by the veh ce manufarturellf
(d) veh.eswithemisson.onlrc coine.ianexau« rhe readinq fa 5outsdethe mirsIven re5etihejet
9* analy5erto the onqine ln a..ordan.e with ihe ådlu5t ng nurtcrew by the minimum amount ne.€sarv
innrumenl manufactureB nstiuctions. ro brinq the r€adingjust with nq the lmit3glven fa.
adjusring ex.eed ng the soew ls requned lo acheive th 5
Sefting .an now .omm€n.e fise.ote.ts€rt ng cånnot rhen the .arbu.elteB mu5t be removed a.d ser!i.ed
b€ obrained within 3 minutes, in(easeihe engrne 3peed
to 2,500 Lp.m for 30 5econd5 and then rE.omme.ce 3.
tuninq.Fepeatth 3 c earlnq operation atl m nute l.teNal5 (al wth th€la( id € (am agar.sl t5relurn slop
untilrunin! c.ohplete. checkthar a1 6mm (l/16 n)fiee movement of
rhe m xtureco.tro moves the.am
ibl PL outlhe mixtlre conirolkhoke) l3lunrilth€
.ka9. is abouiro mole rhe iet
Tuhthelast ld e adjusrlnq screw (4) clockwise
l !nt thecore.tfast"ld e speed isobra ned
G) Adjusr thelhrort e adr6tins rrew (1)unt the veh.lEs 6anuia.tureu recommendation,
Gee
.o ecr dle speed i! obtained Geevehi.le
ldl
manufacr!,ers tuninq datal.
(b) rurn thejetadj.st ns nuvs(rew (2)do!,n/
c o.kwne,lo enr ch orup/anti c ockwGeto weaken,
uitilthe fasted speed i5 ndicat€d;turnihenuV
sdew !!/anll c o(kwise unii the eng ne speedilst
(ommen.e5tofa iunrhe nut4(reudown/
(lockwGevery slow y the min mum amount unill
themaximum speed sregå ned. FromthEien ng
ädlusrhe m rture 5.re!v a(.ordln9 to theveh. e
manufarlu,ers recof mendit on5.
(c) che.ktheldlespeed,aid readlu(ita5 nece$ary
wiih the lhrcttie adjust n9 (rew to obrain the
 3.
Turn therel adjusring iur«rew (l)on ea(h
carburetier down/.lo.kwise to enrl.h or
up/ant . o.(rvise (opweakei, bytie$me
amount unt the tasten speed isindi.åted
rurn ea.h nut/s.rew up/antn orIw3e !nt the
eng ne speed just.ommen.es to fa .Turn ea.h
s.rew very 3 ow y down/. ockw 5e byihe
m n mumamolnrunti themaximuospeed s
re!ai.ed. From th s seiting adjustihe mlxture
s.rews a..ordliq to lh-p vehlc e maiula(tureis
recomme.dätons Gee qråph)
che.k the ldle speed and readrust r as
nece$arywith the throtleadrlrt nq s«ews 1,1)
rum nq each byrhe sameamount

Veh.eswirh emsioncontr.l Us n! theeihaust

9a5ana yser,.her(thatthe read ng i5 wirhin the
mitsg vin n thevehi.le mäflfa.tureatun nq
d3ta.lithe readinq falk ours de the mcgven,
resat both th€ret adrust n9 nurt3cfe!,s by the
m nlmum ånouni ne.e$aryto brlng the
reådlngsiun ur'ithin rhe mits. faiadjustment
ei.eedl.qrhreeflats/häf aturn s,equ edto
a.lrelve ih r, the.arblrette6 munbe renoved

Set the tlr.ottle nterconiectoi.lamp ng

le!o,s r5l,:n a..orda..ewith theveh. r
han!factu,eE f nru.uonr,so thät å. earan.e
exhi5ts betweei ihe nl pin.ndih-aroereredqe
of thefork Ighre.lhe.lampboc enrurns
that there G appror måte y0 8mm il/12 in)end
,oat on the nte(onne.uon od

g c
5
i!n $e e.gife at l,500rp.mänd.h€.kthe
thrott € l.kaqefor co(ect.onnection by
recheck ng the.arbureter ba an.e

wththefast dle.amsoiea.h.arburetter
agalnstthenrespecrvestops, ser rhe co d ståri
l nter.onn€.t ons, sö thstsrl.ams beq n to
'-'" bo' . oLobor. o'rler!'ore hövesmuha.eousy16)
W th th. fasr dle.am! agalnn threr stops

b) S a.ken börh. åhpinq bols12)on thecodnall

ch€clrhara ] 6mm (l/16 n)lree movem.ntof
th€ m xtureconrrollchokel.ableers sts before
interconne.l ons
rhe cable movestha.am
2 (') Pu ofi themixrureco.ifol lchoke) unri the
t5insa bå a.c nq aefiea.cordancewlhthemåketr nkage is abolt to mov€ thejet.
i.5rru« on5, balan.erFe.a.b!rette6 byalter nq the Usinqrhe ba ancinq meireorlisren ngrubeio
ihrort eadjln ng rreu! u.t thecoir.ct dlespeedand en§!reeqLa adrustmeit,turn the fast idle
ba ancei5a.heved Ateriatvely, useå Lten nq tube to adrusti.q5crew5 (7)to glvelhc (otr..tfast ld e
.ompa.etfe nreis ry o,ihe niäiehi55ona
cårburenetr and turnrhethrotte adru(liq «rews u.til (e)
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Earh rl.onra nr eiouqh.ompone*rö
 3r rdteS.rew(it
I
Fast

4 JetAssembty Kit
5 Needje&SearKir 32
3l
7 Th.ottl.spindteKit 34
l5 rhronte/5tärte, Relurn sprnq
xrt

r3 6asker.E.gineFtåfqe
14 l€t Bearjnq Kh 36

b _terLo(k Nut 33
rs MixtureS.rew(ir 19 srafterBod! !s\emb y
a [/t xtlre S.revr
b M xrureS.rewsea
l6 idte Adjusting S.rew Kit 12

a dleAdjusufg Screw 4l
b td e Adtujrnq t.rer spål
l7 3r ,/etätAssemb yt(tr
i 3 irierälA$emb ,
b B Mprr a$embt! SDifo
. 3.Metå A$emblv S.rp;
r3 Ftoatspindte(rr ilare rvpe ba bcannql
^Dampe,
Empmieltyr!pe-bå
a aloar5pindteWasher !eå.nq,

r9 Daoperwasher (where urFnt 50

20 S!.rio. Chamber& 5l Eall-BearfqType5u.ro.

2l SuctionChamb;rS.rews
22 Needl€ Lo.kS.rew
23 NeedleGujd€ (il
a NeedeSpr.g
b Neede6ude
24 Pisron Guide(eyt(it

26

Ihe Need e ltris !n q!e @.",,

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