Cycle News - Archive Issues - 1970's

wonder why this new engine isn ' t dialed in properly to begin with. Compounding the problem of en gine wei ght is the overly heavy chassis , bringing the weight of the 250 YZ up to 23 5 p ounds without fuel. The main culp ri ts here are th e en gine bash plate, st eel fuel tank, and huge bolt toge the r e xpansi on chamber wi th a silenc er so huge it needs two brackets and a cla mp to keep it on the bike. A tremendous weight savings co uld be - made just by replacin g th e step! tank with an aluminum YZ tank of 1975 vin tage, alo ng with the old grenade size YZ silencer in p lace of the present huge canister. The 250 YZ has inherently good handling geo metry , a good front end, the fine monoshock rear suspension and good loo ks. Detailing on the Yamaha is first rate with most of th e minor hassles of maintenance clean ed up and simplified at the factory. Where the new 250 YZ does perform well is on trails, fire ro ads , and just general pl aying ar o und. It's a fun bike to play around on, be cause in true Yamaha fash ion it's a bike that works well and ' re q uires very little maintenance . It's a compromise bike, that for some reason Yamaha chose to label as a YZ for 1976 rather than a MX as they have in past years. Is a new YZ on the way?" Vuor of TheOW25 Since the new 1976 YZ ha s be en dis covered to be a Yamaha MX in disguise, th e possiblity o f Yamaha releasing a new production bike based on the ir latest factory works bikes "is highly likely. Yamaha has always gotten around to selling to the privateer what they race, and a ne w race bike labeled OW 25 for 250cc and OW 26 for 400cc will probably be made available sometime this fall. To get an inside line on what the new production racers will be like, we only need to check out the present fa ctory bike s which Hannah and Burgett are now riding, and Jimmy Weinert used an earlier version of last year to win th e 50 0c c National Championship and the Mid-Ohio Trans- AMA. · · • Rather than a co nven tion al tube frame, the OW works ' b ikes use a combination tube and semimonocoque frame which is lighter and stronger. The frame structure hidden by the tank, seat and side covers is stamped chro m em oly steel, with the airbox being a new high breather design hidden behind the righ t sidecover, The exhaust pipe is a single one pie ce unit that tucks under the fuel ta nk and is easily u nbolted from the right side of the bike . The rear fender is supported by the fram e which extends no further than the rear of the seat. In the suspension department, a n ew monoshock unit used two very light springs to give adjustable spring rates, rather than the single he avy spring used on present Monocross b ikes. The light springs also produce a sm o o t h er ride over the nine availab le in ch es of rear wh eel travel. Surprisingly, the Kayaba air fo rks used on last seas o n's works, b ikes ' an d no w a vailab le on the . production YZ are no longer used on t he present works bike s. T he team is using Kayaba (earling ax le fro nt forks which have internal sprin gs. Su zu ki as well , still uses internal " sp rin gs in their Kay ab a for ks. The Yamaha /Kay aba le ading axle forks give close to 10 in ches of front whe el travel and ar e adj ustable in the triple cl amps for ride hei ght. The 25 0cc version ofth e OW works b ike we ighs in th e n eighborhood of 20 0 to 2 10 pounds depen di ng on how much titanium and du ct tape is us ed on it each week. What a production OW m ight weigh t would depend on whether it became available with a modified version of the present production en gine, or the more exotic and expensive magnesium engine th at the factory is using. Whatever engine Yamaha does de cide to use, the resulting total package should be a lightweight and good handling racer that will reg ain their lost image when it co mes down to selling a ser ious race bike . • Bo b Han nah 's OW 25 is th e be st and lightest mono yet at 209 Ibs. The semimonocoq ue mon osh ock is Yamaha 's b ike of t he future . . .... , \ 25

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