Little Motorcycle Carburetor Manual

8/3/2019 Little Motorcycle Carburetor Manual

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Alii lnform etlon provided ls intended ' f,o :rg :enercd 'gu id !el ines andpractices 'I',orBasic Operation" Tun~ng"and! MaiUil~enanceof Wa.~broPZ S l~deVah re Carburetors.

,Contents:-- -

S A F E l Y 2TUNING

T IJ N I NG lil P S

MAI IN fTE NANCE 7SfFlECllFl lCAUONS 7~OTES 8E XP IL OD ED \tIIEWS

,As witih aflY 'carburetor Q lr fli!le~SystE;!lnl, 'eare I " I i I I l I J i S ; 1 i : betakel'll 10 ilrvoid iiire fl lOMI leakinig 011 ' spiiII!ed tiLlle~. Besure allllgas1 k ru sa lid s es ls E lf'Su n good c on diitija na nd i p ro pe tly a$ smb~edl. D is po se of f a n y drained or S lP i'h3d~uel l .Check co in ditio :n of fu el lin es and con ne cti o ns befOlnil every USEL F uel m us t be drained fro m th e system :i f veh ic le o rengine il s n ot s to re d ow tra ns po rte d ~rl a le ve l p as itio n,It ~s ne,cessaryto c ihe( li k ' tlhe carbl l. il f,e to l l"s li ide f 'Q , r f ree l rt l! lQ I li I'E !I I1 i IIE !! ntlhl l' (l l l!J igh 1ihe f iJ111~.mge Qil ltJrave~all1iYtime 1 i:1 iiI .eambuw ID lr h as b e~ l'fI lr n; I1 'iIO,v ed , ili1 ls ta Hed l~ O r .a d'j; us te eJ an ,( t Itle f,o :r e s ,ta li1 in g U te e li1 lg ~l'I ;e " Removeair f il te randl v isruaJllyconfjrm~h~ slide valve is f lJ~~yclosed as th e throttle is released. Work thethrcnle cornrclffcmc lo se d to fu lly 'Open an d watcn fo r a ny stiding or hang-up" Eng ina s cO ij ll d s ta r t w ith an op e,n t hr ot tle r ;e suJt in g l in auUrl:8!way \! '!{hiGh~.lJlways r~s ta ll t h .e co rrec t re tum spring to r ~hiecar lOt irs~o:rand uSl~naddl it to r iia l mtunn spr fr ilg onthe throttle f;:H~dalla s n eeded.

SAF'ETY

PE :RFORMAACE TUN !NS :2


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TUNING,Rich and Lean: An internal com bustionengine needs a speci'fi:c ratio orm ixture of aJirand fuel! for bestperforrna noe. T his m ixture is d eU vere dby th e ca re u re te r, In 'th e fo llo win gdiscussion nu merous references winbe made to the a ir a nd fuel m ixture(a irr/~ ue 'l ra tio ) b ein g rich o r le an . R ichn:lfers to a m ixtu re with an excess offuel. Lean refeil'S to a m ixture with anexc ess of air.float h,eightParts i involved:: Float linle t N ee dleThe fl oa t F ie il gh t c on tr ols the fuel, levelin th e float bowl. Th is ad ju stmentd ete rm in es the point at which the linletneed Ie opens as the iuellevel dropsin th e bowl. Float heiight is usuall yl lesJsured with the f~olFd:b ow l remo ve d

....Uid i s spec if ied ' fr om tne carburetorDody to an edge or surface on th 'efloat T ih e, flo at sh ou Id be re stl n g o nth e in let nood le but not depressing ~hespring under the needle stem whenthis measurement is taken. 'fa adjust,carefully bend the tab where it makesco nta ct w i,th tne i nl le t need le .The float heigh t should be adjustedbefore any other adjustments arem ade. A high er fuel le ve ll w ill c au sea neher rn lxturs and possibly exc-essoverflow from the vents. A I.ower fuelI level lw i I I a Gause a le an er m ix tu reand cou Id lea.d to an englin e m issor cut-out while oornerinq. Start atthe specified h eight and ch ange asnesded for best performance ond iffe re nt ty pe of tracks.The f J l o a t dr o p should also bechecked. T he pro per a djustm .ent w illiprevent the needle from pulling toofar out 'O f the in let seat and beoom ing

in th ,s o pe n positlon.

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PZ,22- -

PERFORMANCE lUNING 3


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Idl,e and Low SpeedPaints invollvoo':

~ dl :S p ee d Screw, . Ii dl e M i xt ur e Screw ~ i~ot Jet (Ilelle Jet, S low Jet)Carbl.!~tor tu ningl ~t idie and Ilowspeed i s accomp li shed by adjusting~he, lid I e M n xit.u rn S crew, tM P ilot (orI ldl!e)Jet an d kille Sp 'eed Sc rew . Theseadj ustrnents 'wii~contro'l ~dlespeed,idle quaiiilty, and in itial f 'lsponsijvenessJaoce~era tior il o f t he eng ine .The sorew inthecenter oftlhe side,o f tn e caroli.l,retor bodiy ts t ih e f dl 'Speed adjustment:. This screw holdsth e til rattle s!1d e v ,a lv e o pe n s llig hitlyto obtain thie des ire d ,e ngime rpmB it dosoo~hrotrtle.riU!n'llilmi'gtlhe idleS\f jed ~crew dlockwise w ~ n increaserpm . T umin g counter-cloc1kwise \!Vullldecrease, rpm.The Pilot , J l e t is sClrwed into th ecarburetor body and ls located ~nsiidthie float oo wL (S ee ph oto , n ext p8ige,.)The P iil !o t J !e t Il1lelters th e amount offue~entering th e Ibwspeoo' cirouit .A .~a rg i ro r sma lle r je t w il~ change f l. !~~I ()w accorc f r i l g ~ y . , .The sa~e,of the ]et Ii nmil lim,e t: ers is stamped on it.

M IX T UR E S C RE W

U E A !N i -- - - - ~ - R ! e h l

T he Iidle M ixture S crew can b e eith er1 1 l n a Ji r o r fuel adijuiStment s o i t: shoul ldo e , c ie ~e rn lliin oo w ~ at ty pe o ff d ha ng ey(l'Uare making. A m]xtun~lscrew'Onthe ai r filiter side o f th e PZ22caJrbureilOt i s an a ir -o ri l'l y adjustmentso. op ening t~ e scre w ,(Nun ing .co u ntsre lockwise) will in cre as e th eair bleed and lean the mixture. Them~xtu! 'es.crew OF ! the ernginfl)side .,o f~he 1IPZ26carbu re~or is a fM e~adjustment Opening ~hesor:sw willa llo w m .o ,re fuel into th e eng ine for arich er m lxtu r e ofor an initial setting, gently tum themixture screw i r1 I u nti I it IT :g itly se at.s o r

sto P 'S . Baok out the specirfied nu mbero f tu rn s " TheoptimlU rn setting of th emixture screwwJll,1 uS:li.la~1yr~sultnthh ig he s1 rpm w ith , th ie ttilr.o ttile c lo se d..As the aJl1lount of fuel is vari edtiheengine rpm wi I I Ialso va~yWi , th th ro tt lec looedlandl 'eng ine w arm a~d W I .! nningat or s~iglMliy abov desnw,edid~e speedl,slowllytJurn the I die Mbdulr :E l S c w , e w ~nor out to obt.aiin the highest rpm . Thense t the id~espeeds-crew to obta in th edesi r:drpm. .-If a smeo th h::lle,canno t be set wa~ theidle Imixt;urescrew beltween % to 2-}4tums out, or Ilfthe ' el !:g l~~edoes netre .s po nd to a dju stment, a d iffe re nt s iz eP i l'ot J1 et m ay be flooded .T hie p . llo t le tI ,~Ia so called idle Or Slow jat, controlsthaamou nt of fuel at idl~ea)nd Ilhrotl:leposi itio rls up to % open , . .I f t h e - mi:dU!f.eneed le cannot D e . ~earledlou t e ri lo ugh ,a.smaller P i lot J '@ t 8ho~:ld Ibe ~ns1ta lloo l.A I largier Je t should be inlstaUed lifth e m l xtu re is too I'ean.The properPilot Jet=ij11a llo w a sa ti sfa cto rysetting with the mixture screw,.

PZ22

.. .

Mix.tLllw,eScrew

IdleM~xtl lJreScrew

PZ26


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Part involved: Jet Need're.. Mai n Nozzle (N~d Ie Jet) 'T t l rottle Slid~Valve .

The J,et Noodle primar] I y controls fuelflow between 10% and 75% tbrottleopening. The Jet Needle is the longnarrow needle in the center of thethrottle sllds valve. The noodle canbe seen when th e throttle is opened .I~is held ii n place in ' the center of the'throttle slide by a V~s,h;apedclip.T he Jet Needle has five notchesand a C-cl~p which determines theposition of the nedle in the sl idebased on which notch the clip isplaced iln.By varying the height oftheneedle, in relation to throttle opening,the amount ot' taper of t he , need Ie inthe mal n nozzle wi II c h an ge th e fiuelmixture.

To richen the part throttle operation,move the clip to the next lower notch.This wi II Mid th e need I e f arth er o ut:of the mal n nO::l:z:llend a:llow morefuel into the air stream. To ~eanpartthrottie operation move the cl~pto thenext highrsr posm on. T ile notch at 'th etop of the needle would be consideredthe first position Oeanest}. Needletaper reference letters are,stamped 01 1the need Ie for identification.

'% l il HR O T T L E O P E II U NG

RAISING THE NEEDLE IN Tl-IE SLIDE", RICHER MIIXTURELOWERING THE NEEDLE liNTHE SUDE ea LEANER MIXTURE

Location of C-dJip 0 1 1 ' jet Ileedre determlnasmfd -r ange f ue l r ni xh r re ,

Be Sure the V-shaped jet needle retail ii ingi clip isin place and wl~1hold !he jet needlesecurely inthe slide.

Parts Involv'ed: M alin JletThe Malin Jet controls the fuel flowat throttle positions. of one-half to fuHthrottle. The Main Jet is !located insidethe float bowl and is screwed illto thebottom of the Emuls, ion Tube in thecenter of the ca rbu re to r oody . Tinejet size or diameter o n millimeters, iss-tamped on tine jet. A larger diameter]et allows more fuel flow and a richermixture.Ailtitl.ldeand weath,er cone ltlons cana :f fec t the eng ine operatlon e no ug h toIr~quire changing the size 0" the MailnJet. High air temperature, humidity,r altitude CQuld requir'(~a smallerM ain Jet, Low t empe ra tu re , humrd ity "or altitud I woul d requirea largerdiameter Ma.in Jet -

-- - PZ22 I - -PZ26

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RUNNING Tf-iiEENGINE WITH ANI IMPROPER MlPIlNJET COULD RESULT IN A LOSSOF POWI::R. HIGH ENGINE TEMF'EFtATIU'RES, OR ENGINE DAMAGE.

PiEFlFORMANCE lUNING 5


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'TUNING TIP'SGasQI ine ls lhetypiical fuel usedfor in te rna l combus tion engines.. Insome racing appHcaUons methanolalcohol is used for fue l. W h en usingalcohol th e en gin e m us t c on sum eapproximately t\lVice a s m uc h 'fue llaswith gaso lin e , Fo r this re ason someparts need to be r ep la ced f or propertuning. The main nozz le , ma in andpilot jets, and th e Je t nee (He need to0 0 re p la ce d with th e p ro pe r s iz e.I~a.carburetor has been workingwell and then develops a problem,th e most likely cause is dlirt orcontsm ination in the carburetor. Dirtcan p i u g jets or get stuck in th e II "lle tn eBdlle a nd cau se flo od in gl. I t wi I I savetime in th e lo ng ru n to be sure you areworiking with a . dean carburetor.If~he engine performance seems toc ha ng e o r i,d le /lo w s pe ed ru rm in 9

seems erratic, check for IDOsecarburetor and manifold mountingbolts or Ileaking gaskets or seals. Thisca n cause a vacu urn Ieak and leancondition.Symptoms of a rioh mixture are:. Black smok e o r p op pin g ill theexhaust "A ~flait" runn ing enQ line or dulillsound

Runs worse as engine warmsSymptoms of a lean mix tu re a re :- .. High cy l inder head o r e xha us ttern perature. . IBack-f ire/popping from thecarburetor.. H u ns b ette r w ith partial c ho k e., Surging or cutting out

.. Ping ing or rattling s ou nd fromengine under loadThe Pilot Jet, Idle Mixture Screw andJet Need Ie w in h ave th e most effeoton acceleration from closed thr;oUle.

A slightly rich ldls mix.ture may help "acceleration.Mo 'V un gth e p os itio n o f th e J et Neecileclip is a good quick adjustment fo r achange i inair temp ..This will he lp w iththrottle response and c ome r e xit.The Main Jet willllhavethe greatesteffect at w ide open th roU Ie bu t w i ll ialso affect rn ld - ranqe opera ti on .Atter a Ma iln J et change it m ay benecessary to move th e J et Needlep os itio n fo r b es t reeuns,T he o pti m um flo at height settingmay c :ha ng e from track to track . Aro ug h tra ck or a n e ng ine misfiire incertain comers may require a floatadjllstment. If the carb ure to r c an bero ta te d o n the man i fo~d , I t m.ay h elp toturn ttH~carburetora few degrees tocompensate fo r a prob lem corner orfo r oval t racks.

SET-UPThe th ro ttle /p ed 61 1a tio is a n itemth at c an be taJillored to sUlit th edriver's style and beneflt o ve ra llengline performance. By changingthe dlstance from th e peda' pivot tothe point the throtUe cabl e or l inka .geattaches t o . the pedal, the carburetoraction can be slowed down to helpthrottle con tr oll o n a slick o r r oug lhtrack or smooth out a chc ppy driver;rr l iS ~MPORl'ANT TO HAVE PIIflXED8m:)p ON THE THROTliL.E PEDAL.This will reduce wear on the throttlecable and car bu r eto r; R emove theair fi I te r and VlisUiallyconiiirm that theth ro tt le sl id e reaches th e w ide openposition just as th e pedal hits thes to p. T h e s lid e should also funy closewith some s la ck in the cable wi~ th epedal released. Id le spe ed can no t beset i f the pedal is hoh:lijngthe sl idepartially open. .Seal th e pedal end of th e cablehousing from dirt. IDirt will migrate upthe th rattle hous' n ge sp ec ia illy o n adlirttrack. Grit or debris on the sl~deP ERfO RM AN CE TUN IN G 6

OOLl~dcause st icking. A rubber capcan 00 used on th e end of th e cablehOLlslng with a smalll h ole tnrougn i i i :for th e cabl!eto slide through, A dab ofsilicone could also b e u se d a t:th e e ndof th e cable housing . The cable housingshouldaloo besealeo by th e r ub be rboot on the to p of cerouretor cap,F or th e c ab le hook -up, remove th ec ov er, s prin g a nd slide assemb ly . USECAUT ION wh ile u ns crew in g the coveras iii wi IIhave sp ring tension behind~tM ak e a note of the ot ient :a i tion O 'fth e slide valve. T he sm all groove on

th e s id e will align wlth a smal l guidepin lnthe bore. Thread the cable first.thru theboot and cover; then thru th ecenter of th e sp rin g an d fina lly thru th etop of th e slide and h ook the ball endunder the bottom of the slide. {Seephote.)The hose atta.chedl to the bottom otthe carbu retor is for vuel overflow fromth e b ow l. It should bs routed down fo rproper draining.:Fuel pressuriE! requirements are~-3 psi.


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MAIN:TENANCEDrain ing l carbuln!wrThielca~bLlre' torshould be "purged"of alceh cl at th e 'end ot e ve ry d ayof running. A lcoho l is v ery corro siv eand will cause a lot of problems if leftin th e carb, T he fuel line sh ould beun h ooked at ' th,ecarburetor and thebowl d rain screw opened to d rain an yfu el in the s ystem . A noth er option isto ru n the engine on gasoline until its ta lls - Th i s will flu s h any alceh ol outof the s ys tem" T h e c arb u re to r S hlOU l~ da ls o b e d ra ln ed !at least at the end ofth e season whe n ru nn ing 9 'asol ine .FiltersA lwa ys u se a n in ll~ nefu el IiI te r top reven t: eont am in atio n ln sl d e, 'Vheca rbu rete r ;A i r fi I ta rs s ho u Id fit th eca rbu re to r p rope rty and be' kept clean.

Bowl, gasketWhen re~nsta llin g t he flo at bowl yo umay find the gas ket d oe s, not f i tproperly ..If tile gask et is too sm all iltcan be stretch ed to frt the g ro ov e. Ifit is wet it may swe lll s lig htly a nd c arlbe set aside to dn-yand return to thepro per size" If you are doing a lot oi1'disassembly fo r tuning it may help tohave e xtra g as ke ts .Clean~li1gt/lnspeetion.O nee a yeaJrthe carburetor shouldbe d lsasse rn b led fo r c lean inqandinspection. Look for wear on the jetneed h~ an d inlet ti p , In sp ec t a nd /o rrep lao ll l o - rinqs end seals. Ilfclean ingis necessary a . tootnplck will \ ! V O : r k .for c learingl any h oles such as jets.Remov e th e Inlet Needle and use a

Q-tip to c lean tile insijde o f th e inletsea t. C om p re ssed air is also use tu I t oremove contamlnation . The ,p ilo t je thas a v ery sma ll me ter ing orifice. Ilf itcannot be blown ou t il: willi likely needto . be replaced,Always use a stop on the glf3S poo1al.1h~s reduces wear on th e carb u re to rand th e chance of a stuck throttle.

SPEC~IFICATI'ONS PZ26A6:3Maiin Jet 96Pilot Jet; 38Main Nozzlle Diameter: 2_6J,et Needle: GDBle rd notchM ix tu re Sc~w: 1 tu rnF lo at H eig ht: 1 4mm (_550in)

PZ2:2A15Main Jet:9SPillot Jet: 32Ma in No zz le Diameter: 2.6,Jet INeed le : 18GB/2nd notchM ix tu re S c rew: 1 V ; : ; : tumF lo at H eig ht: 2 2.0mm (.8 8DOn )

PERFORMlANCE TUNING! 7


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R . . E . T U i l ; 1 i I~PF!WG

IDI . .lE MiXTUREs(;fI~

PZ26

NOl'IiiS

RETU~~RIr4G

IF1!.OAT~OWL

MAI~JT

PLQTJET

PZ2.2

Walbm IEng_ne ManagemenrltAftermark@t IDiviisionCass City, MI 48726E-Mai l ;[email protected] 11 AutomotlvB Compar ty

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Little Motorcycle Carburetor Manual