YZR250(0WB9）

This model featured further development of the single crankshaft, 90-degree V-twin engine that had been under development from 1987. The frequent crank assembly problems that plagued the 1988 0W90 and 1989 model 0WA7 were solved by a full-scale re-engineering of the crank. Engine vibration was also reduced with the adoption of a coupled-force balancer. Furthermore, rigid engine mounts were used to make the engine a stressed member of the frame, which helped boost handling performance. The 1990 model 0WB9 powered J. Kocinsky to the GP250 World title and its single-crankshaft V-twin engine technology was fed back into the 1991 model TZ250 and the production sport model TZR250.

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