After an impressive debut is international racing at the 1958 Catalina GP, Yamaha next set its sights on an even bigger challenge, the road racing World Grand Prix. A new department was established at Yamaha Motor's Hamamatsu Research Center to work exclusively on the development of factory race machines. The project's first task was to build a full-fledged GP machine that could compete with the world's best. The 2-stroke engine would be Yamaha's power unit of choice, and to it the engineers would bring the latest technology, including the floating type rotary disc valve and independent oil supply.
Then, in 1961, a Yamaha team with five riders including Fumio Ito and Taneharu Noguchi and the newly developed 250cc in-line-twin RD48 and the 125cc single-cylinder RA41 factory machines flew to Europe to make their World GP debut. Their first race was the French GP, round three of the series. Next up was the Isle of Man TT, where Ito placed a respectable 6th in the 250cc class. In that first campaign the Yamaha team entered five rounds of the series but were only able to garner seven series points in the 250cc class and none in the 125cc class.
Nonetheless, the campaign was a valuable learning experience. The development team had identified some specific weak points to work on and important know-how was gained in team management. Although managerial difficulties prevented Yamaha from participating the next season's World GP, that year was well spent in machine development the strengthening team organization. The new 250cc RD56 featured an in-line-twin engine with horsepower boosted to 45PS and a newly developed feather-bed type frame, while the new 125cc RA55 was made significantly lighter.
The RD56 in particular showed tremendous progress, as it powered Ito to podium finishes with 2nd place at the Isle of Man TT and the Dutch GP during the 1963 campaign. Then at the Belgian GP, it brought Yamaha the team's momentous first World GP win. With this, Yamaha and a rider of rare talent had finally reached the pinnacle of the sport.
With buoyed confidence, Yamaha reorganized its team, adding riders Phil Read and Michelle (Mike) Duff. Constant work on the RD56 was improving its competitiveness as the team geared up steadily toward the 1964 season. It looked as if all was set for the '64 campaign, until Ito took a bad fall in an international race in Malaysia just before the World GP season opener. The injuries put Ito out of commission, but Read and Duff would rise to the occasion with outstanding performances that season. In all, Yamaha won six rounds of the '64 World GP series in the 250cc class to take its first Manufacturer's Championship title and Read claimed the Rider's Championship with five season wins. The momentum continued in 1965, as Read and Duff brought Yamaha seven double podiums in the 250cc class, winning eight of the 13 rounds of the series between them. These results brought Yamaha the Rider and Manufacturer titles for the second consecutive year.
The scene change drastically in 1966, however. Honda unleashed a new 6-cylinder machine that dominated the 250cc class. Yamaha tried to catch up by introducing a liquid-cooled V4 engine on the new RD05 factory machine, but it was not enough. Not to be beaten, Yamaha came to the opening round of the 1967 season with a newly developed V4 machine dubbed the RD05A that would hold its own against the Honda 6-cylinder in a highly competitive season that saw the two makers trying to better each other with each race. With one race remaining in the season, Yamaha and Honda had each won six races and Read and his Honda counterpart, M. Hailwood, stood tied in season points with 50 each. The championship showdown was set for the final round, the Japan GP. He race turned out to be one of upsets, however, as both Read and Hailwood no-pointed and the win went to Honda's R. Bryans. Because Hailwood had more season wins than Read, he took the Rider's title, while Yamaha lost the Manufacturer's title to Honda by one point.
In contrast to these disappointments in the 250cc class, 1967 would be the year of a major breakthrough for Yamaha in the 125cc class. After a long dry spell that had continued ever since the start of Yamaha's 125cc World GP challenge, an improved version of the RA97 (rotary valve, in-line-twin engine, liquid cooling) finally brought Yamaha its first GP victory at the Isle of Man TT in 1965. In '66 the momentum built as second-year Yamaha rider Bill Ivy rode to four series wins. Finally, Ivy's big break came in 1967 riding the new liquid-cooled V4 RA31. The new Yamaha machine won 10 of the 12 races of the series and Ivy claimed the 125cc Rider's Championship title with an amazing eight wins.
It could have been the start of a golden era for Yamaha, had not the FIM (Fédération Internationale Motocycliste*) made the decision to put a stop to the factories' race to build machines higher and higher powered multi-cylinder engines. Under the new FIM regulation 50cc machines were limited to single-cylinder engines from 1969 and 125cc and 250cc machines were to be limited to two cylinders from the 1970 season, while 1974 would see the limiting of 350cc and 500cc machines to four cylinders. A limit was also set on the number of gears in the transmissions, at six.
These regulation changes led Honda and Suzuki to announce their withdrawal from World GP racing from the 1968 season. A year later Yamaha followed suit, thus ending ten years of factory participation in the World GP, since its first campaign in 1959. From that point on, Yamaha's World GP participation would come in the form of supplying production racers to privateers.
*Name changed to Fédération Internationale de Motocyclisme in 1998