Cycle News - Archive Issues - 1970's

wrap it around the threads of the petcock before installing it in the tank. (F or y o u cu st o m riders, this works very well to protect y o ur fancy paint j ob fro m fuel th at eats und er the p aint at th e petcock a nd ru ins t he p aint.) ROD QUESTIONS AND ANSWERS By Rod Breaker Hell o. R o d. I have one of th ose twin p ort 250cc CZs , a 1968. As long as / ha ve had my twin port, it has been difficult t o kick start . (Onc e sta rt ed, it b eats most 360s.) Well , I thought the p roblem was carburetio n so I bought a 28mm Mikuni. Th is carb seem ed t o h elp the p rob lem of starting so mc but it is n ot consis t ent. T oday it s tarted on th e third ki ck and was running great . I put in th e right main jet and th e plug, a PA L. was a be autifu l brow n. Everything seemed fine. After shutting it of f and tr y ing to sta rt it again . it wouldn 't. Finally it did start bu t it ran for only a f ew sec o nds and then qu it o n m e at about 2000 rp m , as if th e ignition was shut off. Fifty kicks la ter it started again and rep eat ed what I just ex p laine d. / have heard that th e twin ports ha ve bad ignitio n sy st ems and that I should rep lace mine. But this do esn 't sound right sinc e it has start ed , sometim es. Please help m e. I've had th e problem for a y ear and a half. BR IAN HO UGH Wcst Linn, Ore. I don' t recall an y storie s abo u t twin port CZs havin g faulty ignition systems . You missed a go od ch a nc e to find o u t about yours while you were giving it th e fifty kicks. After the first fe w kicks. you should h ave checked y our igni ti on to see if y ou were getting a go o d spark. First take out the p lug a nd la y it agains t the cy lind er head with the h igh tension lead attached a nd ki ck the m achine o ver to ch ec k for a good st ro ng spark . If y ou do not h ave a go o d sp ar k, this does n ot necessaril y mean th at th e ignition is bad ; it could b e shorti ng o ut inside " e plu g. P ut a small nail - or th screwdriver bl ade into th e plug cap an d hold it a bou t a h alf inc h a way fro m t h e head wh ile k ickin g th e m achin e ove r. Th e spark sh ould jump this gap . (An alternate m ethod is t o t ell yo ur w ife or girl fri end t o h old th e p lug wh ile yo u kick the m achine o ver . Wh eth er o r n o t y ou h ave a p ic k h er up o ff th e gro u nd will attest to th e c o nd itio n o f yo ur igniti on system, but it will n o t endu re y o u in th eir h earts. Besid es , th ey a re only go od for this o ne tim e.) O nce you have asc ertaine d th at you h ave a good spark, y ou ca n go o n t o lo ok for othe r problems. Keep in mind th at yo u o nly need th ree basic things t o m ak e a n eng ine operate, (I) COMPRESSION, sufficient to all ow the mixture to co mb ust. (2 ) FUEL, a co rrect air-fu el mi xture. (3) SPARK. su ffic ien t t o ign it e th e. fuel at th e co rrect tim e. By workin g on these th ree b asic ideas, m o st probl em s o f non-startin g en gines ca n be d iagn osed . You claim y ou ha ve had th is p roblem for a year a nd a half but you don't m ention havin g any e ngi ne wor k do ne o n it . If t h is is tru e, y o u mi gh t not only be lackin g in eng ine compression , b ut yo ur crank seals cou ld be b ad as wel l. This is o ne of th e p rin ciples of the tw o -st roke engine; th ere must n ot o nly be good com p ress io n a bove th e p isto n , but there must b e go od co mpression (a nd a vacuum ) belo w th e p isto n. As y ou may or may not kno w , on a two stroke, th e vacu um creat ed in the crankcase on th e upstroke of the pi st on is what is used to draw the fuel fro m the carb in t o th e bott om end, as the p iston co mp resses th is mi x ture o n the d o wns t ro ke , it is forced in to the co m b ustion ch amber when the pist on passes the t rans fer ports. T o allow the crank to tu rn o n ball b earings a nd st ill have a t ight sea l, each sid e of th e cran k case is sea led by th e use o f a sp ecial o il seal , usu ally having a d ouble lip . If th is seal is o ld a nd worn, it will reli eve the vacuum o n th e up st roke an d the co mpressio n on th e down-stro ke, allowing little o r no fuel t o ge t to th e co m b us t ion chamber. These are a few of the things th at you Can ch eck o ut, but if yo u have been racing it fo r a year and a half an d h aven 't worked the engi ne over, it is probably just go od an d tired . .R O O I am planning to start racin g mo tocross and I have a 1 25 Enduro "w ith an electric sta rter. I w ould lik e to know If there is som e way I co uld h o ok it up so I wouldn't ha ve to use th e battery. Or is th ere someth ing y ou can buy to tak e th e place of th e battcry? ROBBIE STORM San Diego. Calif. ·1 have not had an opportunity 10 h ave to t ry to co nvert a 125 cc Yamah a End uro to a magneto, b ut from previous experience with other makes, you wo ul d have to have th e e nd of the cra n k tu rn ed d own to accep t th e taper of a ma gn e t o fl y wh eel. Th is is o ne di sadvantage of the sta rte r-dyno setup : it seems that the taper for the armature is always di fferen t. I haven't h ad a chance to ch ec k with Yamaha. but perhaps th ey h ave had many req uests fo r th is sa me prob lem a nd have com e up with a magneto to fit that flywheel. I would suggest you check with your lo cal dealer. Whil e th e J apanese generators put out a go od amount of ju ice and y ou may b e able to run it with out the battery, I would not recommend it as it puts quite a strain on the electrics , Also, one icliosyncras y o f t his system migh t b e that you wi ll h ave t o push -start it ea ch time . ROD Dear R od : I ha ve a '6 9 Triu mph TR 6R, single carb o M y problem is a carb f uel leak. I've repla ced th e fl oat and shu toff valve , sealed everything up, b u t I st ill havc a leak . I don't use my bike cvery day . After using it, the leak stops afte r t wo days of idleness, th en it comes righ t ba ck . H op e yo u can h elp m e. I. UCIEN R . B IRON Oxnard, Cali]. Y ou left me a littl e short o n in fo nnatio n. First , doe s it have a rnon oblo c or a co nce n tric carb? O n th e m on obloc, t he usu al fuel leak (othe r th an a bad fl o at n eedl e) co mes either from th e float co ver b ein g tigh te ned too mu ch , th us ca us ing it to warp so th at even a new gaske t will n ot st op th e leakage . o r else fro m th e red fibre was her thaI is between th e carb b ody and th e jet bl o ck . Wh en a rider ch anges th e m ain j et, he will us ually jus t put a wr en ch o n th e je t co ver a n d when he turns it, th e je t bl ock comes lo ose instead. If the re d fib re w ash er is a n o ld o ne , it is sure to leak even th ou gh you tighten it back up aga in a nd the o n ly remedy is to repla ce it. On th e co nce n tric c arbs, th e usual p roblem is wi th th e float c ham ber gas ke t it self. For some reason. t he material that it is mad e from has a te n de nc y t o ge t so ft and so~gy right ov er th e float hi nge p in, allowing the pi n t o raise sligh lIy and th us crea tin g a fl o odin g situa tion th at can be c ured tempo rarily b y re placing the gaske t. You sho u ld m ake a small dimple in th e float c ham b er righ t n ex t t o t he slot for the hinge pin. J ust m ak e it with a small punch o r nail so that yo u h ave to snap the hinge pi n int o pl ace. T he n , if th e gasket go es b ad , th e p in w on't lift. As I said , yo u d idn't give m e m uch in formatio n . You fo rgo t to ment io n wh ere the fu el was leak ing from on the carb o Ano th er fac to r c o uld be if yo u st and it on th e side stand inst ead of th e ce n te r stand, oft tim es this will ca use th e float to can t a bit and create a leak . You also stated th at you ins talled a new sh u to ff valve (by this I figure th at you mean a new petc o ck) . If so, I fin d it hard t o believe that it will still leak u nl ess you are failin g to turn th e valv e off wh en you p ar k it. One la st resort : check to see' if possibly th e fuel m ight be leak ing d own fr om th e t an k around the thread s of th e p etcock a nd foll owi ng the line down to th e ca rb and then runnin g off th e carb to give the illusio n of th e ca rb leaking. This w ould acc o u nt fo r th e tw o da y d el a y in th e leak, if it is slow enough . In stall a new gasket o r red fibre washer u nd er the petcock o r go to your lo cal hardware st o re a nd ob tain so me "ribbon .dop e" used by, plumbers. and Dear Sir: I hav e a Pen t o n 12 5 , 19 72 model that constantly misses gears uihen I downshift. Any h elp you could give m e would b e great ly appreciatcd. A . W. FINGER A us tin , Texas Dear A .W.: T he last wo rd th at I received on the Penton shifti ng p ro blem w as that th e y have "a transmi ssion mod ificati o n th at is supposed t o elim inate it. If your dealer has not received a bulletin on it, you migh t ask h im to inquire about it to the importer. It does so und like your part ic ular prob lem mi gh t b e in . the adj ustmen t of the th ro w of thesh ifter sin ce you have t his problem on the downs hift. You could check this ou t. Congratu latio ns to the Cowboys. RO D Dear Mr. Break er: • I want to put a 500x16 wh eel an d tire on the rear of my Sp ortster. Pleas e advise m e h ow to do this. A lso, I w ould lik e t o put a disc b rak e on th is wh eel. KENNETH RENNES Springfield, Ill . Yo u are gettin g in to th e cust o m field (w h ich is n o t m y bag) but spoking a wheel is a rough job for the beginner for the first co u p le of times . A fter a while it be comes du ck soup. If you really want to d o it yourself, I believe th at Nort h American Imports, Box N , Mojave, CA 9 3501 h as a pamphlet on how to d o it a nd will supply you with the co rrec t length spokes and even the 16 -inch rim if need be. As for the dis c brake, I don't know o f an yb ody th at makes o ne fo r th e Sp ortster, but y o u can co ntac t Howard Barnes o f Barn es All oy Sprock et Sp ecialties, 10146 Stag Sr., Sun V alle y , CA 9 135 2. If a ny body ca n se t you up with a d isc brake se t-u p , Howard ca n. He sup p lies m o st o f th e di sc b ra kes use d b y the n at ion 's t op m otorcycle racers. ROD iii, R od. I wanted to motocross my Ossa Pion eer b u t I suon found out my Tel esco f orks cou ldn't ha ck it . I' ve gut 40-weight o il and 2-ill ch sp acers in each leg and th cy still bottom out ! I just can 't afford new [o rks righ t now but am ge tting desperate. Can you help me ? A T-} C.E. VA R NE L L San F ra ncis c o, Calif As yo u hav e a n Fl' O number, I gathe r th a t you a rc statio ne d o verseas . If this is so. yo u mi gh t b c in trouble , With th e tw o -in ch sp acer s yo u have ins ta lled in th e fo rks , I wo uld as sume th at th e bottoming out that you are experiencing could possibly be c o il bind. (If y o u weigh more than 300 lbs ., forget it.) This means that th e sp ri n gs are too w ea k a nd th ey are just collapsing . Th e only re med y for this is to install st ron ger springs, if p ossible . T ry to obtain so me th at are progressively wound since they get st ro nger as they co llapse more. One othe r th ing co uld be the amo u nt o f oil yo u are p utting in t he fo rks. Ch eck your comprehe nsive owners and riders handbook or contact your lo cal dealer t o m ake su re you are p u tting th e correc t amou n t in to each leg. ROD Dear Sirs, About a month ago in yo ur Hom e wo rkshop you had an article abou t th e Micro-Ti m e. Fo e written th em and ask ed th em if it will work on my Yamaha HT-I wi th th e off -center spark plug but th ey just sent m e sume b ro chu res 011 it. Do y ou kn oui if it will work? ROBERT M. FUDGE Upland, Calif The one d rawb ack of t he Micro-time is the fac t th at if th e plug a ngle is t o o se vere, yo u are apt t o wedge t he pl u nge r instead of p us hing it u p when you a re setting it . The off-se t p lug hole is no t th e determining factor ; what does en ter int o it is th e a ng le o f the d ome o f the piston. Wh ile Micro-Time includ es a form ula to figure the d istance change for th e angle chan ge of the pl ug hole , this can alter if the rod mo ves across a do me. T hey are working on a device t o b e used on these machines, but it will probably require the removal of t he head , or possib ly the rod will b e mounted so that it can sw ivel to a st ra igh t-up posit ion. T hey realize this problem and a re w orkin g on a so lution . As soon as I h ear something, I'll get it in to prin t. ROD AMXT CONTRIBUTORS D ON NOCK , C yp ress, Cali f. ; RICK SIMM ONS , T inle y Pa rk , Ill. ; MIKE WI LLlAMS, Ri ch ard son , T exa s; DO UG ME YER , Sunn yval e , CaUL: E.F . A UGE R, FPO N ew Y ork, N .V .: JOE E . MQR RIS , Win st on Sa lem, N .C.: BRUCE OV E R F I E L D . L as V egas, N ev. : L EO F LANDERS, Joliet , II I .: B EN DRI VE R , T u lsa, Ok la.: MAHLON E . SMI T H , W. L a fa y ette, In d .: WALTER BA RABAS. Melrose Park , III .: RON DO U GLAS, G len do ra , C a lif .: LARRY UL RI CH, Bend, O regon: R I C H A R D C . GISE, G ra na da H ill s, Ca li f.: ROB WE IDNER, Charlotte , N .C.; D E N N I S A . COOPER , Uk iah , c aur.. CA R OL YN M . COONS , Herlong, ce ut .: JIM MEL LO T T, Santa Ana , Cali f. ; A n ahei m , caur. . LA R RY H UF F M AN, R OSEM ARY W I L L M A R C E L L A , R oc kawa y, N .J . ; M .L . B ENNETT JR .. I thaca... N.Y . ; MIK E SWE E T ', Los A nge les, Ca li f . : KAND Y SWEE T , L os Angel es, C ali f . : CONNIE SWEE T , L os Angeles , c aru., PAUL (DUSTY ) S WEET , L os Anqeles , c aur., MERt' LAWW I LL, Tibu ron, Ca li f.: LARR Y E C CLES, So . Pasaden a, C a li f . RO B E R T E . LE E, N o . H ighlands , csur., RO B E R T M. CO O K , Van couver, Wash.; JI M A U ST I N , T ucso n t .Ar iz . ; HOWARD MIL LER, Denver C o tc.: M A R K GANNON, Frazier Pa r k, Cali f.: B ILL ALTERGOTT, B entle y , Mich.: T ONY V OEG E L E J R. , Ba tesv ille, Ind . : DA N IE L O ' B R IE N, Nort h boro , Mass . ; M O TIO N SPO RT S , Da llas , Texas ; ANTH ONY KI W AK , W hit insv il le , M ain e: WAYNE BRASHER , Fre m on t, c sur.. C H A R L E S S . MILLER , C inci nna t i , Oh i o ; R . L. R O B I N S O N , U n io n t o wn, O hio ; R IC H A R D L. ANDREWS , La Mesa, Ca li f. Se n d $5 t o AMXT , B o x 3276 , H oll y wood , C A 9 0 02 8 and help o ur b oy s o verseas. SEE CYCLES ~. WEST COAST NARRATED IN PERSON BY RICH GOLDSMIT a full leng t h fi lm JAN . 26 KLAMATH FA L LS : Tower Theatre 27 STOckton, Civic Au ditorium 30 REDDING, Ci vic Auditorium 31 Feb . 1 SACRAMENTO Memorial Aud it orium FEB. 2 ,3 SAN RAFAEL, Marin Veterans Auditorium 4,5 OAKLAND, Oakland Auditorium 9 M O D EST O, Covell Modesto Thea tr e 10 MONTE R EV , Fairground E xhibi t Hall 12 FRESNO , Commun i t y Theat re 7 & 9 p.m . 14 BAK E RSF IE L D. Ed. Center Aud it o r iu m 15 SANT A BA RBARA . Lob ero Theat r e 20 SAN T A M ONICA, Elks Clu b N o . 906 6 & 8 p.m . 2 1,22 PA SADEN A, Civic A udit ori um 23,24 , L ONG BEA CH, Pacif ic Te rrace Center 2 5 thr u 2 8 DO WN EY . Community T heat re 7 & 9 p.m. M AR .l RIVERSIDE, Riverside Audit orium 2,3 SAN DIEGO, V eterans Buildi ng all shows 8 p.m . except as noted T ick ets at the door or at your cycle shop PRESENTED BY GOLDSMITH PRODUCTIONS in co-operation with THE OLYMPIA BREWING c.OM~A Y ~ 1J, g; N ~ ...: .g u. en a; Z ~ ~ o

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