1983

Throughout the 12-round 1983 series, the Yamaha YZR500s were ridden by Kenny Roberts, Mark Fontan, and Eddie Lawson, who was in his first full year in the GP. The OW70 spec YZR500 used this season was the second-generation V-4. The new model featured a Deltabox frame and a 17-inch front wheel. The championship title became a two-man contest between Roberts on the Yamaha and Freddie Spencer on Honda with its V-3 engine. Both riders' results were even, with six race wins, three 2nd place finishes and six pole positions. This was a tight battle of a kind never before seen in the history of GP racing. Roberts missed out on the title and was allotted to 2nd place in the overall ranking by a deficit of just two points. Lawson finished the season in fourth.

The championship decider was in the final round in Imola, San Marino in September. Up to this point Spencer had won six races and Roberts had won five. Spencer was leading the championship by five points, and Roberts had to gain five points more than Spencer this round. Even if Roberts won the race, Spencer only needed to finish 2nd to take the championship. Roberts started the race in pole position and ran a faultless race to take his sixth win of the season. Although Lawson was one of the favorites to deny Spencer 2nd place, he finished six seconds behind Spencer in 3rd. This handed the championship to Spencer.

This season began with tough competition, as three different riders won the first three races (all on the Yamaha TZ250). Carlos Lavado, winner of the third round, was able to come out on top of the competition. He won the fourth round in West Germany, and although he finished in 7th for the Spanish and Austrian GPs, he won the seventh and eighth rounds in Yugoslavia and the Netherlands. Consistently adding to his points tally, he climbed to the top of the championship ranking. After coming 3rd in the ninth round in Belgium and 4th in the following British GP, he was able to clinch the title before the end of the season. This made him the second Venezuelan world champion after Cecotto. Yamaha also won its second consecutive manufacturer's title.