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Phil Aynsley photographs the Kawasaki 250cc S1R – A bike that does not officially exist!

It’s not often I have a chance to photograph a bike that doesn’t officially exist!

The 250cc 1972 Kawasaki S1R
The 250cc 1972 Kawasaki S1R

Despite Kawasaki’s denial that the bike ever existed, this 250cc S1R prototype was constructed in 1972 (together with a 350cc triple).

1972 Kawasaki S1R
1972 Kawasaki S1R

Correspondence with riders in Japan has revealed that both bikes were tested at Suzuka but proved to be not competitive against the Yamahas of the time. The factory chose to focus on the H2R project and the two smaller triples were shelved.

1972 Kawasaki S1R
1972 Kawasaki S1R – Two models were produced but proved noncompetitive for the time
The engine featured a one-off six-speed gearbox and dry clutch
The engine featured a one-off six-speed gearbox and dry clutch
The chassis is from a A1RA/F5R
The chassis is from a A1RA/F5R
1972 Kawasaki S1R
1972 Kawasaki S1R

This bike was then shipped over to Mack Kambayaski in California to see if he could develop it further. It raced once, at Virginia International Raceway, but was not successful.

1972 Kawasaki S1R
1972 Kawasaki S1R
The crank used the type of orange-ringed non-spin bearings that are found in the 500 and 750 racers
The crank used the type of orange-ringed non-spin bearings that are found in the 500 and 750 racers
1972 Kawasaki S1R
1972 Kawasaki S1R

Although it was only a prototype for testing, Kawasaki invested quite a bit in the engine. The gearbox is a one off six-speed unit, the crank uses the type of orange-ringed non-spin bearings that are found in the 500 & 750 racers. The dry clutch is also a one off unit. A H1RA ignition is used. The chassis is from a A1RA/F5R.

1972 Kawasaki S1R
1972 Kawasaki S1R