| Kawasaki 1967 F21M Green Streak |
| Kawasaki’s first purpose built off road racer was the 1967 F21M Green Streak, a 238cc 4 speed, 35 horsepower spindly framed rocket that terrorized riders and competitors alike. The Green Streak had the right formula of weight and horsepower going for it, but lacked something very important in an off- road racing motorcycle: handling. |
| Kawasaki produced the Green Streak for flat track and short track competition, and kept the overall design of the motorcycle as simple and light as safety would allow. The four speed rotary valve motor pumped out an impressive 35 horsepower at 6500 rpm, and was housed in a lightweight frame that made the bike a force to be reckoned with on the flat ovals it was designed for. But put that same motorcycle on an MX track, or in the desert, and serious handling shortcomings became apparent almost immediately. Spindly forks and shocks, along with under designed frame components, that looked more at home on a 100cc bike, made the Green Streak an evil handling beast when a bump was encountered, as the frame and swingarm flexed like a wire coathanger under the high output of the motor. And since the bike was designed for flat track, the steep fork angle made the bike a head shaking handful, that required a steering damper large enough to slow down the frantic tank-slapping, that would appear when slowing down from speed. |
| The early Green Streaks had problems with excess flashing on the case castings breaking off, and getting stuck in transmission and primary gears, along with rotary valves disintegrating from flaws in the phenolic disc. Also, swingarm mounts cracked, and rear hubs exploded under hard use, along with frames cracking at the steering head. Most of these problems manifested themselves when the bikes were motocrossed, or raced in off- road competition, as the Green Streak stayed pretty solid on a flat track. The F21M was produced for five years, with little change or improvement done between the production years to address these issues. In 1972, the Green Streak was replaced by the F81M 250 MX. A portly bad handling motorcycle who’s only saving was the rotary valve design of the motor. |
By Matt Cuddy #MC 1