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Originally posted by: Froooo
First off, there was never a CR 426. When Yamaha developed the original YZ 400F they were the first Japanese co. to produce a serious 4 stroke mxer, & if I recall correctly the AMA hadn't set the displacement limit for the thumpers to race in the 250cc class at 450cc. At one time I believe it was closer to 500 cc but nothing was set in stone as of 1998. Yamaha updated the motor to a 426cc in 2000 & it got a bigger clutch & bigger radiators too. Doug Henry's early race bikes were said to be at 426cc...they were still trying to get the right bore & stroke where the motor worked the best. Honda actually had a say in having the limit set at 450cc....they are on the Board of Directors at the AMA...so when the finally decided to release a 4 stroke, it was a 450. Right now, Yamaha is developing a 150cc 4 stroke racebike to compete in the 85cc class....Honda is said to be on the same track too..........

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