This is a rare bird, it is a factory prototype S1R, yes a 250cc triple "R". In 1972 after the success of the H1R and the launch of the S1, S2 and H2, the Kawasaki developed the H2R and they also developed one prototype S1R and one S2R. The S1R and S2R were tested in Japan, however, neither were competitive with the equivalent Yamahas of the time and the project was scrapped.
As a last attempt the S1R was shipped to the famed tuner Mac Kambayashi in southern CA. As the AMA did not allow 3 cylinder engines in the 250 class it is unclear if the bike was ever raced in the US.
The engine is housed in a A1RA rolling chassis which was originally ridden by Dick Hammer in 1969 and 1970, and features a special 6 speed gearbox and dry clutch. In H2R style the two outside cylinders are swapped so that the exhausts exit between the frame rails. The carbs are from an H2 and the ignition from a H1R.
As purchased before restoration.
The engine after its restoration and rebuild.
August 07, the engine back into the frame, the rolling chassis upgraded to its original F5R spec.