Product Review

This issue of The Motorcycle Files is centred upon a track test by Alan Cathcart of the only surviving example outside the factory of Yamaha’s ultra-rare rotary-valve square-four. This 500cc OW60 is the GP racer that was owned by French Yamaha importer Sonauto and on which Marc Fontan placed tenth in the 1982 World Championship standings.
Despite Yamaha being massively outnumbered by strong Suzuki opposition, he finished in the top ten in eight GP races and also rewarded Sonauto with the French National Championship.
Only eight examples of the Yamaha OW60 were ever built and they were to all intents and purposes an outright copy of the rival Suzuki RG500 which, with its rotary valve induction, had outclassed Roberts’ 1980 World Championship-winning piston-port OW48R for speed.
Kenny only rode the OW60 square four in one Grand Prix, using it to win the opening round of the 1982 season in Argentina. After that he concentrated on developing the OW61 vee-four – not an easy task as it turned out, as he never won another GP that year.
The Yamaha OW60 square-four did, however, have its moments in the sun. In 1982, Crosby won the prestigious Imola 200 and was runner-up in the World Championship. Then in both 1983 and 1984, Kenny Roberts won the equally-important Daytona 200 (in 1983 and 184) on the OW69, a bored and stroked 695cc version of the OW60 that produced 175bhp!
In fact, all things considered, the Yamaha OW square four was a bike that could have been a World Champion but which was never given a fair chance in the hands of the top rider of the day.
Subsequently Yamaha was left to ponder what might have been had ‘King Kenny’ not been sent off down a blind alley with its vee-four successor.