Crank & piston assembly from 1965 Honda RC115, factory GP racer.
49.75cc, 15bhp
@ 20,000 rpm. 9 speed gearbox.
This is what it lived in..
Bicycle style rim brakes save weight!!
(big hub disc is just for aerodynamics)
The year after, they got 16bhp @ 21,500rpm. A bhp per litre figure unbeaten to date!
Read more on Honda's 1960s racers HEREDifference between the RC115 and the RC116 is a new bore and stroke, now being 35.5 x 25.14 mm. Power output is 16 bhp at 21,500 rpm. This means 320 bhp per litre and a Pme of nearly 16 kg/cm2 ! As regards bhp per litre, this is a figure that has never been surpassed by any naturally aspirated four stroke engine, and even today's formula 1 cars with their special fuel brews cannot hold a candle to it. I know this is not a totally fair comparison, but it gives an idea of the level of four stroke technology nearly 40 years ago. This engine is the most advanced of all the Honda engines. Red line at 22,500 rpm. Carburettors have flat slides. The gearbox contains a nine speed cluster. Dry weight of the bike is 58 kg. The piston pin has a diameter of 9 mm and weighs 6 g. The inlet valve head is 13 mm, the exhaust valve head is 11.5 mm, and the stems are 3.5 mm diameter. Weight of the exhaust valve: 6 g.
