Cycle News - Archive Issues - 1970's

I from the ca rb m ou th to th e piston skirt. Match and po lish the exhaust tract from cylin der liner th rough th e exha ust flange and into th e pipe. Ma t ch the transfer ports from th e cases to th e cylinder lin er a nd fr om the cases to th e cylinder ports. Do not try to en large or reshape any of th ese passages at th is time. but rather co ncentrate on smooth ing th em and elimi nating over hangi ng gaske ts and mism a tch ed openings. I If you r engi ne u tilizes a rot ary valve inlet you ca n streamlin e it's inl et tract from carb mouth through th e engi ne cases a nd mo d ify intake timing- in de pendently of exh a ust a nd transfer tim ing by cu tting material from the ope ni ng and closing edges of the valve. W.ork in known inc rements of either decimal in ch es or cran k d egrees . a nd sbek competent a dvise b y those familiar with your sp eci fic eq uipment before sta rt ing . ' Bend ing th e grou n d elec trod e of you r fa vorit e plug ou t to whe re you ClIO file it s hor te r so that its end exact ly a ligns over the middle of the cent er electrod e provid es better sp a rk an d fouling resistance, next to that of the fine-wire types a t half the price. AC pl ugs have th is feat ure sta nda rd on th eir two-cycle a p plica tions. I ha ve never fou nd a use for th e re tracte d ga p plugs ofte n recom mended for j apa necse pe rfo rmance engi nes . Ditch these h igh -price . fas t foul ing ( raci ng?) plugs in favor of a like heat range co n vent iona l p lug. If th e p lug threads extend into the co m b ustion sp ace of your head you shou ld space the p lug wit h a single copper was her of the req ui red thickness so that the plug end is just flush with t he hea d surface . Never used any other than high test. leaded gasolin e in any m otor cycle , regardless o f manu factur er recommendations . By and large , top pro tu ners ag ree that des pi te th eir disadvan tages th e Castor based ' lubricants still p ro vide t he best engi ne pro tection . but t he n if all tuners agree oil every thi ng th er e would be no suc h thing as tuning . I Low buck mods I Typ ica lly for aro u nd $10 you can ha ve a com pe te nt machinist m od ify your cylinder head to pro vid e an imp ~oved co m p ression ra tio or co m bustion chamber sh a pe . If you h ave a racing orien te d d eal er cha nces a rc he ca n provide you with speci fica tio ns for just suc h a mod ificti on . If you r sp a rk p lug is recessed ins ide it's tapped opening into th e co m bustion cham ber now is th e tim e to have th e amount required to bring it flush with th e chamber machi ned fro m th e plug gaskl,'t sea ling su rfa ce . Many larger replacement carbs a re sifupl y bored versions of the same ca" tings with correspond ing metering s incr~ases. Determ ine if vou can bo re yout ca rb by co m paring it to a like model of the size desired. Most 30 . 32 and 34mm carbs are m achin ed from th e same casting . as are most 36 and 38 m m carbs ma chined from the next larger cast ing . Boring you r ca rb " sho u ld cost around $ 10. T he most effec tive proced ure a t mini m u m cost to ei the r inc re ase overa ll speed or accelera tion ( pick one) is to in cr ease (for speed) or d ecr ease (for accel eration ) the tooth co u nt on t he co u n rersh aft sprocket. T his typ ica lly cos ts arou nd $5. 1 11'have purposel y refra in ed fro m co m plica ted . costly or spec ia lized modi fications particu larly co nce rni ng resonan t tu ni ng of th e int a ke a nd exha ust , to fa vor sim plici ty for t he beginning tu ner. H opefull y suc cess and sa tisfac tio n in early tu n ing ven tures will lead th ose so in clined to seek furth er kn owled ge . I would recom mend th e purch ase of H . P. Book's T wo Strok e Tu ners Ha ndbook by Gordon J ennings . • ------ ..._- II you must go faster, think first how you'll look in plaster. r-----------.., I .,~.~ o 'T"",.. ~ i ~~ BUL.T~CC :r..... I I Competi tion Motorcycles I I Sales Parts - Service I Mail Order Service I I a Specialty SALES OF DALLAS I • . 0 » II l II Try us first for the hard to find Bultaco parts 1176 Mississ ipp i. Dallas. TX 75207 (214) ___.. . . . 638·2010 . ! .J ~--..-----' - I[!lUlcK R , ~® [[j) [P)@jlkT O 1 . Van Suspension Kit 13920S.W, Tualatin Valley Highway Beaverton. OR 97005 503-646-8600 iff"" 'lAMA l-f.l t;~ SPECIALS . Hustl er He lmets reg . $21.95 sele $14.95 Teem Logo Jerseys reg. $13.95 sele $8.95 Std. NGK Sperk Plugs reg. • 1.25 sere .6~ Name Brand Leathers • . . , . ,'•• •. . . ... .•. . , . , .. • .. . . . . . . ...• . , . , .. .•. • • . . . . 25% off Nylon Leethers , , . . . . . .• . .•. •.. • . • . .. 25% off Meny more it em s on sale Li mi t ed to stock on hend No ma il or phone orders .....__..... T&OYAMAHA 24020 Narbonne Ave. (Torrance/Redondo area) . Lomita. CA 90717 WO RKS PERFORMANCE PROD UCT S 213-534-2311 * * 4 H U R HIPP IN G PARTS - ACCESS OR I ES Rebuilt Eng/nil E~rhdn l/t'.s Hen('1 11 RIVcrc,jlj.· Par il l d M ,Jr."O C.. '11 : Plrpl : 1 ~.1V A4 "~td ';Id, Ho rn') Har r u t al.jr ; ' ,j n, : h>'; () r!o ° 'V!lHI' l l Reqina Chdin '\;[) I-'lu'lS A i;V Hplnll't<. ll c rr a r u C.I(oI!()(1 n l f l l <; $ 1.00 C OS M O PO LI T A N M O T OR S , INC , H a t b o to . PA 1904 0 /2 151 6 72 9 10 0 17

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