"A motocross marvel," raved Motocross Action when Yamaha's YZ426F made its debut almost three years ago, while Dirt Bike hailed it as the bike that "changed the motocross world forever." Doug Henry merely drove home the point by winning the national outdoor title in '98, the 426's first full season of national competition.

For 2000, Yamaha has bored out the revolutionary ultrashort-stroke, liquid-cooled, five-valve thumper. Dropped in a new 39mm Keihin flat-slide FCR carb with a throttle-position sensor and a newly integrated carburetor hot-start button. Reshaped the silencer. And tweaked the gear ratios in first and second while beefing up clutch capacity with larger, stronger plates. The result? A sharp boost in power and throttle response and a super-broad, Kansas-flat torque-band.