The Yamaha 0W35K for 1977-78 was the machine with which Kenny Roberts clinched his first of three successive World Championships after having won 4 GP's with it in 1978. This was the bike that used for the first time the "Powervalve" system, which was already tried on the Motocross machines. According to Shiohara-San, one of the engineers, the Powervalve contributed more to the increased performance than anything else before. Johnny Cecotto also won 2 GP's with this machine.

Yamaha 0W35K, 1977-78