Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/127172
carburetor is m uc h lar ger to improve airflow. In th e transmission department, the clutch has a new p ull- type rackand-pinion clutch actuation mech anism for easi er a nd smoother clutch operation. A two-piece clutch cover is now found on the YZ, so th e clutch innards ca n be exa m ined without having to rem o ve the com p le te clutch co ver assem bly. G ear ratio s have been slig h tl y ch a nged . The p rimary reduction gearing is slig h tly taller , as is the first gear ra tio . The YZ's coo ling system received a larger left-side ra dia tor for more water ca pacity, a n d is m ounted 40m m low er in th e fram e. The bigger and stronger swingarm has new push -type chain adjusters and a beefier chain guide. Test: 1989 Yamaha YZ125W The comeback kid By Kit Palmer Ever since losing its stronghold in the 125cc class back in the late '70s, Yamaha is hoping to reach the end of the comeback trail with the release of the all-new, 1989 YZ125W. Not only does it have new look s, bu t it finally features a refurbished motor and th e latest in . sus pensl.on tech nol0?y' T~ese lo n g- awa ited ch a n ges Just might advance th e Yamaha back to th e front of .th e ~ Iass: Just Iike ItS ':lIg broth er last year, th e YZI25 received a com p lete face li ft for · 8~ . Redesigned f~nders , gas ta n k, rad ia tor sh ro uds,. Side panels a nd graph ics a re th e ob v.lOus changes th at grace th e eye-ca tch in g Yamaha , bu t an inve rted fork a nd a 19-in ch rear wheel will ca tch th e attention o f th o se who ta ke a closer look. . Engine The 1988 YZ h ad a potent motor but Yamaha went searchi ng for even more horsepower and left no stones u n turned in the hunt. The new YZ has what Yamaha calls a "TZ-style" cyli nder, which shares dimensions with th e Yamaha TZ250 road race cylinder. The cylinder bore is l a r~er a t 1 2~ . 8cc, a n d ha s a composite cera m ic coali ng to reduce overa ll weight and improve heat dis sipation, Beca use of the new coating. the o ld h eavy steel cylinde r liner is no lo nger used. . The piston received a few modification s to improve reliability and performance. It's now 2mm shorter from th e wrist pin to th e crown for grea ter stre n gth, a nd four hol es in th e p iston provide lu bri cation. A (Left) The exhaust p ipe h a s h ig h e r ground clearance a nd the clutch has easier access. (Bel o w) An inv e rt e d cartridge Kayaba fork absorbs the pounding u p front . Ilauer crown is used to in crease com pressio n. Port in g has been slig h tly res ha red to en hance top-end p erformance, a nd th e exha ust port is rea ngled to ra ise _th e exh a us t m anifold, thus impro vin g ground clearance o f th e exhaus t pipe. The YPVS power valve was fiddled with to create better low- end reponse. The exhaust pipe is all new. It has 22m m more ground clearance a n d has two new mounts (instead of one), one far forward and a second near th e tail co ne. A larger aluminum silencer is used. Feeding th e co mbustion chamber with th e proper fue l a nd ai r m ixt u re is a new fla t-slide 35mm TM Mikun i ca rbur etor, wh ich replaces last year 's ro u nd-slide Mikun i. A larger ai rbox is now used and the rubber boot co n necting it to the Chassis Frame ' a nd chassis changes are near id entical to th e ones made on th e 250. Like th e YZ250, the 125 co mes stock with th e upside do wn Kayaba cartridge fork. The upside down design reduces fork flex which im p ro ves front en d stability and cornering, and since the fork tubes no lon ger ex tend be low the fro nt axle, there is reduced ch ance of the bottom fork tubes ha nging up in ruts while leaned over in turns. The fork h as external com p ression da m ping adj us tments, a nd the stan ch io n tu bes are protected by plastic gua rds. Since the upside down fork is stronger in design , more stress is put on the fra m e, so the frame has been beefed up, as wel l. The front down- , The le ft rear sub-frame section can be removed for quick and clean access to the Kayaba shock. Carburetion is handled by a 35mm Mikuni. ·