By Richard Fowler of Motorsport Retro—This exquisite piece of rolling sculpture is Yamaha’s 1975 YZR500. It’s the OW23 variant, the machine that took Giacomo Agostini to the last of his incredible 15 World Championships. Making its first appearance in the 1974 Belgian GP, the OW23 was designed specifically for 500cc Grand Prix racing. (Its predecessor, the OW20 TZ750, was based on a planned but never released road bike). Under that curvaceous fairing is a traverse water-cooled two-stroke in-line four. This beautifully engineered powerplant delivered a stunning 95hp and revved to 11,000 rpm. It propelled the white, red and black racer to an eye-watering 170mph top speed.
A major weight reduction program was a factor in the YZR500′s success. The twin-loop steel tube chassis was light but strong. Aluminum calipers were used up front, the wheels were cast magnesium, and the rear suspension was via a weight-saving monoshock. Other innovations included a cassette-type transmission that greatly reduced maintenance time.
The OW23 may have delivered Agostini his last title, but for Yamaha it was a first. It was the company’s first 500cc World Championship win, and also the first for a two-stroke. If you were lucky enough to visit the 2010 Dutch GP, you’ll have seen Agostini reunited with his bike (below). It was the return of two legends that changed Grand Prix racing forever—and I have to say, both seemed to be in pretty good condition, 35 years on. [See more vintage motorcycles at Motorsport Retro, the online celebration of motorsport from the 60s, 70s and 80s.]