Kel Carruthers won the 250 ccc class in 1969, riding a 4 cylinder Benelli, the last time a 4 stroke won the 250 cc GP class. This is an exploded view of the motor, based on a large one piece aluminum crankcase casting with holes covered by a rectangular pan and four round covers, through which the crankshaft, seven speed transmission and clutch were assembled. A large aluminum oil pan bolted to the bottom. There were four separate cylinders with right and left cylinder heads. The cams were driven by a three gear train and there were two valve and four valve versions.
In 1970, the class formula changed to two cylinders and six speeds which favored the Yamahas and Benelli withdrew.
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