The Yamaha RA55 125 ccm was the improved version of the RA41.

With a bore and stroke of 56 x 50,7 mm respectively it appeared at the end of the 1962 season and was used very shortly in 1963 as its successor, the RA75, with an 8 speed gearbox instead of the 6-speeder for the RA55 could be entered already in the second-half of 1963. Both the RA55 and the RA75 were only used in Japan as a test-bed and therefore never appeared outside Japan.

Yamaha RA55 125 ccm