Cycle News - Archive Issues - 1990's

ha s almos t too mu ch to p -end a n d H on da is looking for more bo tto m-e nd p ower, that lea ves th e YZ2 50 somewhe re in the middle, which cou ld be the best compromise of all. The bike barks and pu lls hard , even in the loa m ies t, p o w er-r o bb in g s ituations a n d s till, so me how , man ages to re ta in the tra ctable label. That's good stuff, there. The clutc h and transmission we re left alone this year, and no complaints were reported , either. It was notchy shifting at first, but a little break-in time cured this and the bike shifted fine u nde r full load s. Yamaha ke pt m ov ing along wi th development of the frame and suspension components, brin ging the rake in half a degree (from 27.7 to 27.2 degrees) and reducing the tra il by 4mm (from 122 to 118mm ). This was don e in an effort to quicken up the hand ling and cre ate a roomi er riding area. The riding position was made roomie r, since the geometry ch a nge moved th e h a nd le ba rs 4m m higher and 10m m forward. Th e swingarrn-pivot bolt wa s increased in diameter (f ro m 17 to 18mm ) fo r in cr eased rig idity , and the beef ed -up upper -shock mount ha s been relocated 6mm closer to the centerli ne of the bik e. Th e 46m m Kayab a fork is all new , featuri ng an increased d iam eter for th e da mping cartridge (fro m 28 to 32mm ), and re ceived a ne w o u ter-tu be shape. The pisto n was also increased in size in accord ance wit h th e car trid ge, as was the midspeed valve (from 25 to 27m m). The va lvi ng was also Changed to provide more consisten t d amping acti on, and kudos to Yamaha for the addition of a n elas tomer bottoming system much lik e rea r s hoc ks hav e been u sing for years . This "wo rks-type" bottoming system a ba ndons the oil -lock bottoming sys tem in favor of a cush y piece of rubber in each leg. The end resul t is bet ter bottoming control, since elastomer is not s peed -se ns it ive and yo u d on 't he ar metal-to-metal contact or clanking noises w hen bo tto ming, bu t ra ther a smooth thud . The forks still use the .43 kg /mm springs used last year. In the rea r, Yamaha opted to use the sa me link that the race tea m ha s been using all s eason o n its w orks bi kes . While the overall wheel travel rem ain s the sa me (12.4 inches), the shoc k stroke is now 6mm longer (from 126 to 132mm) to reduce ope rating temperatu res by lowering th e s haft s peed . The s p r in g rate ha s b een d ecrea sed fr o m 5.2 kg / mm to 4.8 kg/ mm to match the new leverage ratio, but effectively, the rear is (Left) New 46mm Kayaba forks that feature an elastomer bo ttoming system. and race team-s pec su spension linkage In the 'rear (Abo ve) Tester Don Burl

• Cover