The Yamaha R5 350 Twin

Yamaha had introduced its first “big” 2-stroke, the 305cc Big Bear, in 1966. That was followed a year later with the all new YR1 Grand Prix, whose short-stroke 348cc twin benefited heavily from lessons learned on the track, and finally, in 1970, the YR5, or the Yamaha R5 350 as it was known in the states.

The Yamaha R5 350 was in many respects the crown jewel of Yamaha’s continuing 2-stroke program. While it put out the same 36hp as the previous year’s twin, an increase in torque and other refinements meant it easily boasted the best performance of any 2-stroke Yamaha had ever made.

Where previous Yamaha 2-stroke twins had been very peaky, with a narrow power band ushering in a rush of acceleration at high revs but leaving engine response flat at lower engine speeds, the R5 could deliver usable power from as low as 3,000rpm, with peak torque of 28ft/lb developed at 6,500rpm. For the average rider, this was a huge improvement. Gone were the days of having to rev the engine to a scream before slipping the clutch to achieve any sort of smooth, low-speed take-off — or to pull cleanly once on the move. “The R5 pulls like a 500 when you twist the grip in fifth,” said Cycle World in appreciation of the R5’s low-speed engine performance.

Yet with the throttle cracked wide open it would run as fast as bikes twice its size. Get the revs up over four grand, and the R5 350 became a different machine — and it produced performance numbers to prove it, consistently running the quarter mile in the low 14 second range. That was on a par with Triumph’s 650cc 4-stroke T120, then a benchmark for performance.

Yamaha also applied lessons learned on the track to the R5’s duplex cradle frame, which drew its basic design from Yamaha’s successful TR2 race bike. Strong and rigid, it was far less prone to flexing than previous frames, resulting in the best handling Yamaha road bike ever and a machine the editors of Cycle Guide considered “a real contender for those interested in production-class racing. The chassis is absolutely rock steady. So much so that the rider gets a distinct impression that the wheels are running in a slot.”

Although no featherweight, at 322 pounds dry it was hardly a porker. And with a relatively short 52.8-inch wheelbase, it was a pretty good wheelie machine, too. So much so the folks at Cycle World found themselves wishing Yamaha would stretch the bike out a bit to help keep the front end on the ground. “Shortness, coupled with the strong power range, had us leaning forward to keep the front end down during hard acceleration,” they said.

Although electric starters were fast becoming de rigueur, Yamaha, perhaps to bolster the R5’s performance image, went with kickstart only. Testers hardly complained, and in fact asserted that an electric starter would be wasted on the R5, given its propensity to fire easily and immediately first time every time, regardless of conditions.

Power was routed through a slick-shifting 5-speed transmission universally praised for short, precise shift throws, while a twin-leading-shoe drum brake up front and single-leading-shoe drum in back pulled the R5 to a stop. Although a few early tests cited poor feel and performance from the front brake, Modern Cycle loved it, saying the front brake “will collapse the front forks and all but smoke the front tire under hard use.”

Yamaha wisely changed little on the R5 350 during its three-year production. With the exception of a larger taillight for 1971 and different color options, the 1972 R5 was the same as the 1970 model. As fast as the market was changing, Yamaha still appreciated the value of continuity.

Although many collectors will tell you the later Yamaha RD350 and RD400 are the Yamaha 2-strokes of choice, it’s hard to find fault with the R5. True, body parts are getting hard to find, but growing interest in the model coupled with a surprisingly high survivorship mean you can usually find whatever parts you need to keep your 21-incher on the road.

Two-cylinder Rivals to the Yamaha R5 350

1968-1973 Honda CB350
– 36hp @ 10,500rpm/90mph
– Air-cooled 325cc OHC parallel twin
– 5-speed-drum brake front and rear (disc front 1973)
– 344lb (dry)
– 45-55mpg
– $500-$2,500

When Honda introduced the new for 1968 Honda CB350 (and its CL350 Scrambler variant) at its annual dealer convention, every single dealer stood up and applauded. And not just because they liked how it looked; they could see instantly that this was a bike that would make them money, and lots of it.

The CB350 was a truly modern machine. Instead of the ring-dingy and smoky 2-stroke found in most small bikes, the 350 had a positively exquisite OHC 4-stroke twin that redlined at an incredible 10,500rpm — and it would do so willingly — yet would pull happily almost from idle. The CB350 provided cheap but sophisticated power for the masses, and buyers flocked to Honda dealers. Over a six-year production run, more than 300,000 CB350s rolled out of Honda dealerships and onto the highways and byways of the U.S., making the 350 without question the most popular motorcycle of its time.

Outside of the expected yearly color options, Honda changed little on the 350. Transmission gear ratios were subtly altered for 1972 with wider and more even spacing between gears, and the redline was brought down to 9,200rpm, a belated recognition of the fact that many riders were routinely over-revving the twin. A disc front brake came in 1973, but otherwise Honda left the 350 alone. Still cheap, but rising steadily in value, it’s one of the great bikes of all time.

1967-1971 Bridgestone 350 GTR
– 37hp @ 7,500rpm/95mph
– Air-cooled 345cc 2-stroke parallel twin
– 6-speed
– Drum brake front and rear
– 354lb (dry)
– 40-50mpg
– $1,800-$4,000

The Bridgestone 350 GTR was the company’s one and only attempt at joining the 21-incher club. Better known as a tire manufacturer, Japanese Bridgestone first got into the motorcycle game in 1952. Although motorcycle manufacturing was never a major part of the firm’s business, it was a profitable venture and the company continually looked to expand its market.

Developed specifically for U.S. buyers, the 350 GTR was presented as a full-size motorcycle for the mature rider. Performance on the strip and the street was impressive, with quarter-mile times in the low 14s and a top speed of around 95mph from the rubber-mounted 37hp 2-stroke twin. Technical innovations included aluminum cylinders with hard chrome facing for tighter tolerances and a 6-speed gearbox. GTR owners also had the unique option of swapping the shift lever and rear brake lever to give left or right gear change.

The motoring press praised the GTR, but an as-introduced price of $900 kept sales low. The story goes that Bridgestone was eventually pressed out of the motorcycle business by Honda, who suggested the company should decide if it was more profitable to keep supplying Honda tires or building motorcycles.

A combination of relative rarity (there were only around 9,000 made) and high owner loyalty have kept prices relatively high. Even so, reasonable examples come on the market regularly, making the Bridgestone an intriguing option to the standard Japanese fare. MC  

Read more about the motorcycles mentioned in this article: 
The Yamaha RD350 
The Bridgestone 350 GTR