On what make of motorcycle did Barry Sheene win the 500cc-world title in 1976 and 1977?

Barry Steven Frank Sheene (11 September 1950 – 10 March 2003) was a British professional motorcycle racer. He competed in Grand Prix motorcycle racing and was a two-time world champion, winning consecutive 500cc titles in 1976 and 1977.

Sheene was signed by Suzuki during the off season 1972–1973 and won the newly formed Formula 750 European championship for them in 1973. As a works Suzuki rider Sheene had two contracts, with the World Championship events taking precedence over his Suzuki GB contract for home and International events, if any race dates clashed.

For 1974, Suzuki introduced the RG500 which Sheene rode to a second, third and a fourth scoring 30 points and finishing sixth in the World Championship. A spectacular crash at the Daytona 200 in the 1975 season threatened to end his career, breaking his left thigh, right arm, collarbone and two ribs, yet he recovered and was racing again seven weeks afterwards. Again riding the RG500 he scored an impressive first 500cc victory at the Dutch TT.

In the 1976 season, he won five 500cc Grands Prix, bringing him the World Championship. He took the Championship again in the 1977 season with six victories. For the 1977 season Sheene was partnered by Steve Parrish, who rode Sheene's 1976 Suzuki 500 cc machine.