Reference: Japan’s famous racing four

by

250cc Honda four racer

Last year's star racing power unit, the Honda two-fifty four earned its laurels by both speed and reliability. As this drawing shows, the engine follows orthodox design apart from employing four valves per cylinder – unusual when the bore measurement is only 44mm.Honda 250cc four cylinder racing motorcycle engine With a stroke of 41mm the engine is slightly over-square.

Drive to the twin overhead camshafts is by a train of spur gears located between the inner cylinders. The cams operate direct on inverted cups which fit over the coil valve springs and bear in the cam-box housing.

Article continues below…
Advert

Enjoy more Classic MotorCycle reading in the monthly magazine.
Click here to subscribe & save.

Cast-iron skulls form the combustion chambers in the light-alloy head and the chambers are of pent-roof shape closely matching that of the piston crowns as illustrated.

Unlike the 1960 carburettors which had guillotine slides, the instruments used in 1961 have cylindrical slides; the float bowls are underslung and surround the mixing-chamber bases to help immunise the fuel-air ratio from high lean angle variations.

The engine produces about 45bhp at its peak of 13,500rpm. bike
 

Article continues below…
Advert

Advert
Subscribe to The Classic MotorCycle Magazine Enjoy more The Classic MotorCycle reading in the monthly magazine. Click here to subscribe.

Article Tags:

About the Author