Cycle News - Archive Issues - 1990's

xplained the ex tensive modifications hat his bike had und er gone. At that mo ment, we knew th a t we ad to have a 167 of our own. Thou gh ur YZ 125 test bi ke ha d al ready been ully modified by R&D Racing, we felt hat the extra grunt produced by one of eterson's mons ter s would be th e hot icket in Vet class action. A new cylinder as ordered from Yama ha , and our bike as off to see the wizard . Peterson starts by splitting the cases. er the crank is balanced and stroked, e then m achin es th e engine cases in rder to allow the repositioned ro d to lear t he center cases. A m o d if ie d ola ris s now mo bile p is ton is slap ped nto the rod and mated to the cylinder, hich is bored ou t 6mm, ported and epla ted with Nikasel. In order to allow he ta ller pi ston to clear th e cyli nd er ea d, th e co mb ustion cha mber is esha ped and a small , barely noticeable pacer is inserte d betw een the cases and linder. The power va lves are modified o accep t the larger piston, but are other. e left stock. "We played around exte nsively wi th ower-val ve tim in g a nd s ha p e , b u t ound that th e stock settings work the t," sa id Peterson. Like the power valves, the carburetor left stock, with the exception of a few 'nor jetting cha nges. Peterson mated he cylinder to a s ta nda rd FMF Gold eries ex haus t p ipe, ut retain ed the stock ilencer. After dyno testing ur com pl eted motor , eterson rep orted that ur bike pumped out a ealthy 38 horsepo wer t t he rear wheel. ite an im provement ver the stock 28. With th e n e w ou nd power, we figred that a new set of prockets were in rd er. Renthal Chain heels are the choice f the majority of the act ory teams, so w e pted to fit a p a ir of he popular sp rocke ts n ou r machine. Ren hal se n t u s their new tralight countershaft procket, which is claimed to be lighter nd stronger than th e stocker. Th ou gh eterson reported that the new motor -oul d pull taller gearing, we d ecid ed to tick with the stock 13/ 50 com bination. Renthal also thr ew in a pair of Mike iedrowski-ben d handlebars, as well as set of med ium-com pound half-waffle rips. Being unfamili a r with the ne w iedrowski bend and lon gtim e fans of he old 722 version , we were ske ptical at irst, bu t were soon won over by the omfo rtable ben d of the MK rep licas . As for the res t of the machine, Whi te ros. su p plied a set of purple and white o fenders, radiator shr ou ds and sideanels to give our bike a differ ent look. h e UFO pl a sti c fit lik e a glove, and ade our slightly hammered bike look ike new . N -Style Im pact Graphics round ed out th e look of th e Yama ha. Pro Plates contributed a trick set of cus tom-m a d e n u m b ers to comp lete the race-readiness of ou r Vet-class weapon. A sly smile cr ept ov er our faces as we fired up the YKP YZ167 for the firs t tim e . The bike emits a throaty bark, unlike the high -pitched whine of a sto ck 125. It' s an odd sensation at first - the ike rev s like a 125, yet has p ower delivery like a 250. Peterson built the ike with the intentions of retaining the Zl25's excellent powerband, and w e Renthal Mike Kiedrowski Replica handlebars and hall wallie gr ips provide a comlortable control layout. Power was put to the ground via a set 01 Renthal Chain Wheels. So lar, sprocket lile Is excellenL ruinin g th eir motor. Maintaining h is mad -scien tist image, Peterson has also ex p erim en ted w ith alco hol, and h a s reportedly go tten his bike to register 42 horsepower on the dyno , Converti ng you r Yamaha YZl25 into a YKP167 cos ts $1250. It sounds steep, b ut w h e n you co nsider that the fee includes all the parts and abo u t 19 ho urs of labo r, the hefty price tag seems a bit more reasonabl e. Peterson is also quick to point ou t that rep airing a blown up 125 is also expensive, as the cost of a new rod kit, piston , cylinder, head and cra nk - pl us labor - will cost at least $700 at most deal erships . "A guy wi th a grenaded 125 wou ld be crazy no t to spend the extra money fo r a 167," r ea s o n s Peterson . "Why s pend th at m u ch and get t he sa me amou nt of power? Why no t go for the 167 and have a bike that rips?" (Left) The extra 43cc gained with the YKP mod ifica tions are very noti ceable , especially when tract io n abounds. YKP' s Chr is Cooley puts the bike through its paces. What they cost YKP 167KIt•••. •••.• . . .••.•• . . .. . ..• .••• .. . .•. •••.•• .$1250 FIIFGold Sllrles Exhaust. •..• •. . . ..• .. .. .•. •. ..•. .. . .$169.99 N-StyIe ImpIct GnIphlca . . . ••_. .• . .. . . .. .•. •.. ...•... .$59.95 N-Style Pre-Cut NumberpIaIe Backgrounds ... ••.•...• .•. .$16.95 N-Style SwIngarm Decals KIt ... • ••• ••• . . . . ••••. . . .•.•.• .$9.95 Pro P111lel1 Custom NumIIefs .$2.50each UFO Front Fendllr .$26.15 UFO Rear Fender .$26.92 UFO Side Panels .$55 UFO RIIdlIlor Shrouds , , , .. , .. , , , , $45.77 RenlhaI Mike Kiedrowski ReplIca BanI $79.95 RenlhaI Medium Compound HaIf·WaIIIe Grips ••• .• , .. , $9.95 Rentlial RserSprocket .$56.95 Rsnthsl UItrIllght CountershlltSprocket . •. . . . . . ••.. . . . .$25.95 . . . were pl ea santly surprised to d iscover th at he was quite successful. The YKP bike m a in tains the stock YZ's power delivery characteristics - it's not ex tra FMF · YK Racing P pipey and hard to ride like some modiiOll W. san'Bernardino Rd. 25930 Belle POrte : fied 125s we've rid d en . On the other Covina, CA 91722 . Harbor City, CA90710 hand, tho ugh, the bike didn't have gobs 8181967-0736 3101539-6884 of low-end torque like one migh t expect. The bike did have more low end White Bios. AxoSPorl America than the stocker, mind you, it just didn't . . 24950 AnzaDr. ' . 24845 Cortlij PI. . . have a super-chuggable feel. Instead , Yorba Unda, CA 92687 . . Valencia, CA91355 . the bike has a healthy, revvable power805I25Hl474 . 7141692-3404 . band tha t ma kes it m u ch easier to go fas t on. It was possible to ride a gear Pro Plates ' N·Style : highe r th an n orm a l, but installing a ·27811 Avenue Hopkins #2 -; P.O.Box.911 .: smalle r rear sprocket allowed th e bike Valencia, CA 91 355 . Mt won, PA 17347 to make b etter u s e o f its im p roved 717 1266-0268 . . 8051294,1 .118 po we r. We switched to a '49-too th rear .. sp roc ke t, and th e bi ke pulled it w it h ' ease. against 250- and 500-m ounted Vet ridWe ap precia ted the 167's extra power ers. O n th e tra ck, the bike enjoys th e most o n s u percross-s tyle track s . Th e best of both worlds - the light w eight newfound grunt instilled greater confiand flicka bility of a 125, and th e extra d ence in our testers when it came time power of a big-b ore. to power out of a tigh t corne r and over a We were also overjoyed to find tha t double jump. The extra bit of low end th e b ik e ran p erfectly o n pump gas. gained makes it easier to maintain tracKnowin g well the hig h price of race gas, tion in the d ry, as the 167 doesn't exhibit Peters on build s h is b ikes to run on as much wheelspin as a stock 125. su per unleaded gasoline. Sure, the bike The YKP YZ167 wou ld repeatedly wi ll run even better on race fuel, but at run dead eve n in drag races agains t a least 167 owners ha ve the option of runstock YZ250, and to our delight, the bike ni ng sta ndard fuel without the risk of y ie ld e d a hol es h ot in our fi r st race Whoya' gonna'call? YKP also offers a mil der, 139cc versio n that costs $650. The mo difica tions are all top-end related (piston, cylinder, head), and splitting the cases is not necessary, hence the lower price tag . Also , Peterson makes 139cc kits for Kawasaki, Suzuki and Honda 125s. No, the 167 is not legal for competi.tion in the 125cc class, but we do feel that there is a definite demand for such mach in es . O nl y a small percen tage of motocross bikes in the Uni ted Sta tes are actually raced - most of -'hem end up on the trails or in th e desert. Play ri ders w ho bought 125s a n d wish they ha d purchased 250s will love the YKP kit, as will Vet class racers who favor the ligh t w eight and handlin g characteristics of 125s. Several ra cin g cl ubs offe r 200cc class es at grand prix events, and most end uro and off-road even ts have similar di visions. But if you' re thinking abou t building a 167 and cheating with it in th e 125cc class, keep in mind that the 167 sounds a lo t more powerful than a typical 125, and that alone could be a dead gi veaway. Und er those circumstances, we at Cycle N ews could ha rdly recommend such gamesmanship. Still want to give it a try? More power to ya' ... Literally.

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