Development of Light-weight 250 cm3 4-stroke Engine

The 250 cm³ 4-stroke engine, which is lighter in weight than the 2-stroke engine, was developed as a means to improve the overall performance of a motocrosser.

It was a widely accepted opinion that the 4-stroke engine come out heavier, in general, by approximately 20% than the 2-stroke engine. Challenging this opinion, we carried out our task under the design concepts of:

1. 1)
   Making use of advantages of the 4-stroke engine.
   Lightens the crank web and crankcase by reducing the moment of inertia and reduces the height and weight with the use of a very short stroke.
2. 2)
   Turning disadvantages of the 2-stroke engine into advantages.
   Lightens the driveline components, pistons and crankcase components with the use of a design adapted to the output.