1984

After Kenny Roberts' retirement from GP racing at the end of the 1983 season, Eddie Lawson and Virginio Ferrari became the Yamaha factory riders. The YZR500 had undergone further development as the 0W76 spec. The valve system was changed from the rotary disc valve system, which had a top speed advantage, to the reed valve system, which had a wider power band and good starting performance. The main rival this year was still Honda, with riders were Freddie Spencer, Randy Mamola, Raymond Roche and Ron Haslam as the chief rivals. Honda also introduced a new machine powered by a V-4 engine. Suzuki did not enter the competition this season as a factory team, but Barry Sheene participated in the GP on a Suzuki anyway.

Lawson, now in his second year in Grand Prix racing, won the opening race in South Africa as well as the ensuing rounds in Spain, Austria and Sweden. He took his first-ever GP title with a consistent performance of four wins, four 2nd places, one 3rd place and three 4th place finishes. Ferrari in the meantime finished the season ranked 7th. Honda clinched the manufacturer's title with four wins by Spencer and two by Mamola.

The opening round was held in South Africa under rainy conditions. Spencer on the V-4 Honda retired due to machine trouble. Lawson kept Roche at bay and took his first win of the season. In the second round in Italy, Spencer ran a fine race and won with a margin of around 20 seconds over Lawson in 2nd. Spencer sat out the third round due to a painful foot injury, which occurred before the third round in Spain. Here, Lawson stayed ahead of Mamola and Roche to take his second win of the season. Lawson continued to race strongly in the following round in Austria to take his third win. Spencer then won the following three races in West Germany, France and Yugoslavia. After seven races, Lawson had three wins to Spencer's four. However, he had managed to stay on top in the season ranking from the opening round.

Christian Sarron, who had finished 2nd in the ranking the previous season, rode the TZ250 again to claim his first championship title, winning three times and finishing 2nd four times to run up a tally of 109 points. With this, Yamaha won its third rider's title in a row and tenth overall. Yamaha also achieved their third consecutive manufacturer's title this season. Sarron finished the opening round in South Africa in 2nd making a good start to the season. However he finished outside the points in the following round in Italy. After finishing 2nd once more in Spain, he took the second win of his career in the following Austrian GP and rose to the top of the season ranking. He also won the next race in Germany and increased his lead in the championship. Except for the race in the Netherlands, Sarron consistently finished races in high positions. In the Swedish GP he crossed the finishing line in 2nd after giving away the win to his rival Manfred Herweh (Real). The title was his before the season was over. Carlos Lavado from the Yamaha team finished 3rd in the championship ranking with a single win along with two 2nd and 3rd place finishes. The AMA Superbike Champion Wayne Rainey participated in the series on the TZ250. He finished 8th overall, having scored a 3rd-place finish in the Italian GP.