Yamaha RD350

Giant killer

| January/February 2010

Yamaha RD350
Years produced:
Claimed power: 39hp @ 7,500rpm (claimed)
Top speed: 95mph (period test)
Engine type: 347cc air-cooled, 2-stroke parallel twin
Weight: (wet) 352lb (160kg)
Price then: $1,071 (1975)
Price now: $1,500-$4,000
MPG: 35-40

Contrary to popular opinion, there’s no evidence supporting the idea that the “RD” in the Yamaha RD350 model designation stands for “Race Derived” — but race derived it certainly was.

Yamaha jumped into racing in Japan as soon as its first motorcycle, the 1955 125cc YA-1 “Red Dragon,” was launched. Early ventures into the U.S. racing scene were successful enough to encourage the company to widen its horizons. Yamaha factory rider Fumio Ito might have won the 1963 Isle of Man TT aboard the 250cc Yamaha RD56 if it hadn’t been for a bungled 50-second fuel stop. And when Ito was sidelined by a crash in 1964, Phil Read went on to take the 250cc Grand Prix world title. Yamaha factory teams continued to dominate the 125 and 250 classes at world level until 1968.

350cc or bust

Despite the early racing success of Yamaha motorcycles, it took a privateer team to crack open the 350cc class. In 1967, Canadian Yamaha importer Trev Deeley modified two 250cc Yamahas, punching them out to 350cc, and entered the U.S. racing scene with riders Yvon DuHamel and Mike Duff. DuHamel led the Indy National briefly that year before crossing the line just behind Cal Rayborn riding a Harley-Davidson 750, while Duff qualified second fastest at the 1968 Daytona 200, which Rayborn also won. The giant-killing era of the nimble 350cc 2-stroke was underway.

In 1967, Yamaha launched its first 350cc street bike, the YR-1. As little more than a big-bore version of Yamaha’s 250cc twin, the YR-1 can trace its ancestry to the YD-1 of 1957, which Yamaha engineers designed after carefully studying the M250 and racing RS250 twins from Adler in Germany. By 1962, the 250 had evolved into the 19hp YD-3 roadster with a pressed-steel backbone frame and electric start, and it was joined in 1963 by the sporty (but kickstart-only) 25hp YDS-2.

The big development came in 1964 with the YDS-3. Until then, almost all 2-strokes were lubricated by mixing oil with the fuel, a tiring and haphazard process that also required always having a bottle of 2-stroke oil at hand. Yamaha’s innovation — called Autolube — was carrying engine oil in a separate tank, injecting it into the engine at the carburetor by way of a small oil pump driven by the transmission input shaft. The fuel/oil ratio was determined by engine speed and throttle opening.

Richard Backus
1/14/2010 10:38:11 AM

You're right of course, Alex, the R5 didn't have rotary valve induction but rather was piston ported. How we missed that is beyond me, but pretty dang embarrassing. It's been corrected in the text, thanks for pointing it out. Richard Backus/Editor

Alex McLean
1/12/2010 10:13:45 PM

Come on you guys who wrote this article, when you announce that the R5 had rotary valve induction and that the RD series went to reed valve you kind of loose some credibility. Thats more than a typo, it sounds like someone filling empty space with drivel, someone who really did not do thier homework. I know you guys can do better

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