Starting on the drawing board and tested by KHI at Kyoto university as first a large air-cooled twin, a V-3 configuration or parallel triple, the H1 as we know it was eventually created as a high performance three cylinder, piston ported two-stroke. Early testing dictated the innovative use of electronic ignition to deter low speed plug fouling and the design goal of 120bhp per litre was achieved.
The W1 continued in production for some considerable time and was even produced in later life as a police specification machine complete with front twin disc brakes.
The H1 was hailed as the “world’s fastest accelerating street bike” producing 60bhp from 500cc and achieving 13 second standing quarter mile times.
As famous for its “interesting” handling as its sheer outright performance, the H1 was gradually refined and finally phased out in 1976 as the KH500 due to stricter noise and exhaust emissions legislation.