YZR500(0W54)

Introduced at the same time as the 0W53, the 0W54 mounted Yamaha's first square-4 engine. The intake system was also changed from the existing piston valve type to a rotary disc valve type that gave better power development characteristics in the high-speed range. K. Roberts used the 0W54 from the opening round of the 1981 series and scored consecutive wins in round two, the West German GP, and round three, the Italian GP. After that, however, a string of bad luck caused Roberts to end the season ranked 3rd. Meanwhile, B. Sheene, who also began to use the 0W54 from round four, the French GP, scored a win in the final round, the Swedish GP.

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