1966

In 1966, Yamaha aimed for a third consecutive rider and manufacturer title. The V4 powered RD05 was used to compete in this season. Ace rider Phil Read was narrowly outpaced by Mike Hailwood on the 6-cylinder Honda, resulting in 2nd place for both the rider's and manufacturer's title. Read finished 2nd in the ranking with notable performances including five second-place finishes. However, in the final round in Japan, Yamaha riders Hiroshi Hasegawa, Read, and Akiyasu Motohashi dominated the podium, which brought high expectations for the following season.
The Japanese GP was held at Fuji Speedway. The Yamaha riders were Hasegawa, Motohashi, Read, and Ivy. From Europe, Aermacchi, Bultaco, and Husqvarna brought in their factory machines. Yamaha riders took control of the race from the start, while competing with each other for the lead. After a fierce battle with the defending champion Read, Hasegawa clinched his first GP win in his home race. Read followed Hasegawa to the finish while recording the fastest lap of the race at 2'05.87. Motohashi finished third.

Six years after its first entry in the French GP in 1961, Yamaha began competing in the GP125cc class for the entire season. The RA97 with its liquid-cooled, 2-stroke, 2-cylinder engine and 8-speed transmission, which had been making progress in its second year, was brought in as the season's race bike. Out of the total of 10 races, Yamaha's Bill Ivy took four wins, which included his first GP win, and Phil Read took one win, while Honda's Luigi Taveri took five wins, giving the season title to Honda. Yamaha's Ivy was ranked 2nd, only four points behind the champion. Despite this, Yamaha's Ivy and Read made a one-two finish while holding off their competitors on Suzukis and Hondas to win the TT race of the Isle of Man for two years running.

The season-opening Spanish GP was held in the Montju?c Park Circuit located in a suburb of Barcelona. Apart from the three Japanese manufacturers, 36 bikes including Bultaco, Montesa, Derbi, EMC, and MZ joined the starting grid. Riders from Suzuki and Yamaha, MZ, and Honda, with its 5-cylinder engine, formed the top group, but it was Ivy who came out in the lead in lap two when other riders who were competing in the front of the pack started to drop back. Ivy continued to run in good form throughout the race to take his first-ever GP win. Read had to return to the pit early on in the race and have a spark plug changed, which dropped him to the back of the pack, but he showed a remarkable recovery and finished 4th.

In the 350cc class of the final round of the season in Japan, Yamaha introduced the RD05A with an enlarged displacement, which Phil Read and Bill Ivy took to the finishing line in first and second positions respectively. This win was the first in the GP350cc class win for Yamaha.