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/126625
C("') 00 Q") Irnpression:,1983 Yainaha YZ125K Light yellow headhunter By Lance Bryson Photos by Jim Bowman and Bryson After seemingly being caught asleep at the line in the 1982 125cc class wars, Yamaha has come back with a vengeance in the new YZ125K. In producing the latest one-eighth 10 liter YZ, Yamaha sa ys th ey had three goa ls in m ind: to lighten it (they claim 190 pounds dry), to lower the center of gravity, and to impro ve per form an ce. After riding the bike, we' d say th ey've sue- " ceeded. In lo wering th e center of gravity, two areas received a major change, the rear suspension and the watercooling. The rear shock and linkage have been redone to allow th e sh ock to sit lower in the frame. In ad dition the sho ck has 15sett ings for compression damping a nd 20 for rebound damping a nd preload adjustment. Last year 's fork-moun ted single radiator has been scra p ped in favor of frame-m ounted dual radiators. This no t on ly helps to lower th e center of gravi ty, but keeps th e rad iat o r- generated heat from affecting the action of the forks. . Even the I23cc engine has been the target of weigh t reduction efforts. The cylinder head is smaller and more rounded, and overall thickness has been reduced both in the cylinder head and th e cylinder. Even thecylinder studs have been changed from 10mm to Smm, again to save weigh t. Yamaha tech whiz Ed Scheidler, the co m pany's version of the Shell answer man, says, " An y area that we could find to cut weight, even if it was only five or 10 grams, we did it." Even the ignition cover has been changed from aluminum to plastic. The combustion chamber area has been reduced to raise th e compression ratio. Because of th e variable exhaust port afforded by the Power Valv e, th e compression rat io ranges from 7.S:I to 9.9: I. Another problem area on the 'S2 YZ wa s with th e rods and bearings. According to Scheidler, " It stemmed from th e way th e bearing manufacturer was making th e bearings. There seemed to be three high points that were causing all the seizing problems. That has been taken care of, plus we opened up the oil pickups from 12 to l6mm for better lubrication." The airbox has been moved from a side panel to right underneath the seat. Two bolts hold on the seat, and once they're off, air filter access is very easy. All aboard Sitting on th e YZ is no problem if you 're Mike " T oo Tall" Bell, but test riders under 5'S" could onl y get one foot on th e ground at a time. Positioning of th e controls was spot-on for our testers. Starting was no problem ; choke on, three kicks a nd the engine breathes life through it s Mikuni VM34 ca rburetor. Yamah a 's new quarter-turn thrott le asse m bly is effo rtless to use. H eadin g to the track, you'll dis-