Yamaha RD350

Giant killer
By Robert Smith
January/February 2010
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The Yamaha RD350.
Photo by Robert Smith
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Yamaha RD350
Years produced:
 1973-1975
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.

The only problem, however, was that the pump ran off the input shaft, which meant no oil was pumped when the bike was stationary and in gear. This was, presumably, to avoid over oiling at traffic signal stops, but could starve the engine of oil if it was revved sitting at a light with the clutch in. Even so, it worked well enough that before long most larger 2-stroke Japanese road bikes were using a version of Yamaha’s Autolube system.
In 1965, Yamaha introduced its first bigger banger, the 305cc Yamaha YM-1, which lasted two seasons before being replaced by the full 350cc YR-1. Next to arrive, in 1970, was the 5-speed Yamaha R5, produced until 1972. The next year would bring bigger changes.

The first RDs
For 1973, the Yamaha 2-stroke twins took a huge leap forward with the RD250 and RD350. The big change was the move to reed valves placed in the intake, replacing the piston porting used in the R5. Importantly, this allowed Yamaha engineers to significantly revise port timing, for a much more civilized engine with more thrust and a wider powerband — without mixture being blown back through the intake, a common occurrence in the earlier engines. 

An extra cog went into the transmission to give six speeds, while up front a disc brake provided the extra stopping power this now potent package needed. For the final 1975 model year, when Ian Swift’s RD350B, our feature bike, left the Hamamatsu factory, nothing much had changed from the 1973 bike but the paint schemes.

The Yamaha RD350 was universally lauded by the motorcycle magazines of the day. “Take the RD350 out on a favorite stretch of hilly, winding road where the 6-speed transmission and powerful front disc brake can be used to their fullest, and you’ll find a race-bred motorcycle in a street machine’s clothing,” said Cycle World, while Cycle Guide noted, “It’s only natural for any street motorcycle with a road racing heritage to also go fast and handle well. The RD350 does both.”

The magazines found little to criticize on the RD350 except its cold-blooded starting habits, which required full choke and a one-minute warmup before it would take any throttle, although Cycle voiced a dislike for an over-use of chrome and vivid graphics: “The Japanese have been ‘improving’ style for the last three years by simply doing more of it. As soon as they learn to do a little less, their bikes might begin to have as much visual appeal as some of the British machines. Until then, Wurlitzer city.”

Wreck recovered
If the silver-and-black graphics on Ian’s 1975 Yamaha RD350 B look less familiar, that’s because the ex-Brit painted the bike as he remembered the RD350s of his youth in “the old country.”

“I have a romantic recollection of bikes from the mid-Seventies,” says Ian, a former Royal Navy engineer from Sheffield, England, now living in Victoria, British Columbia, Canada. It was a 250 belonging to his brother that introduced Ian to the RD series. “I pottered about with them and took them to pieces, and kept them going back then,” Ian says. “I’m just rediscovering and re-honing those skills. So I generally stick to the ones I know, which is why I do 2-strokes.”

Ian remembers a motorcycle store in a town close to where he grew up. On display was a silver RD350 that Ian coveted, but couldn’t afford to buy. “I’ve got this vivid recollection of seeing this showroom full of bikes with the 350 Yamaha in the middle and not being able to get at it,” he says. “So when I came across this one …”

The RD350 featured here was one of a pair that Ian discovered in a wrecker’s yard in Victoria. Ian offered to buy both machines, but the wrecker was determined to part them out. Ian watched as the bikes kept shedding parts, all the while trying to persuade the wrecker to sell him what was left. “This went on for more than a year,” he says. “Eventually, I think he must have needed some money, because he sold me one of them. But then I had to re-find all the parts that had been dismantled from it.”

Restoration and more
Since then, Ian’s Yamaha RD350 has received a complete nut-and-bolt rebuild, with NOS (new-old-stock) replacement parts where possible — “I like to use the original parts if I can,” Ian says — and all the fasteners and chrome parts were replated. The engine was treated to a rebore and new Wiseco pistons, while the frame was powder coated at Victoria Powder Coaters — plating and polishing was done by Victoria Plating. One item not taken care of locally was the fork stanchions, which were sent back to the U.K. for hard chroming. Ian has found hard chroming — commonly used for hydraulic cylinders — to be very expensive in North America, so he takes advantage of visiting in-laws to have parts shipped to the U.K. “There are more niche industries in the U.K. that do things like machining,” Ian says.

Stainless spokes for the wheels came from Buchanan’s Spoke & Rim Inc., and the wheels were trued by Ian’s local bicycle shop. “I respoked them, but I’m not very good at truing,” he says. Period Avon Roadrunner tires were an eBay find, while many obscure parts come from Action Motorcycles, a Yamaha dealer in Victoria, after Ian identified the part numbers from microfiche diagrams he found on the Internet. “I just give the guys the parts list and they order them, even obscure rubber pieces,” he says. “Even if they come from Japan, they only take about two weeks to get here.”

Ian recovered the seat himself using a repro seat cover, while the decals came from Sunrise Graphics in the U.K. For the paint, he worked with Perfections Custom Paint in Victoria. “Getting the right shade of silver was difficult,” he says, “because the only guides I had to work with were period photographs.”

Ian credits two other companies with helping him find NOS parts, “Like the top of the airbox and some of the rubber bands that keep things in place,” he says. Many of these came from Speed & Sports Inc. in Bloomsburg, Pa., and from Northwest Vintage Cycle Parts.

Worth the work
The Yamaha started third kick after the restoration, and Ian has found it attracts attention wherever it goes. “The real trick is finding them these days,” he says. Everyone remembers them, but can you find one with all the pieces on and complete and working? You can’t. As people come to realize that, I guess they’ll become rarer and rarer. It certainly resonates with a lot of folks as I ride it around. It seems to be a bike that a lot of people started their riding careers on.”

The Yamaha RD350 is just one of many classic strokers Ian has restored, including a Kawasaki KH400, a Suzuki 500 Titan, a Vespa 150 and a Suzuki GT750B. Ian is using the revenue generated by selling his restorations to help pay tuition costs for the Ph.D. program he’s presently enrolled in. “Think of it as innovative financing, if you will,” he says.

Many people seem to lose money restoring bikes, especially when, as Ian does, they specify NOS parts. So I asked Ian what his secret was. “You don’t factor in the time you spend doing it,” he says. “If you did, it would be a hopelessly loss-making exercise. If you classify the labor as a hobby, it works. I find it therapeutic, too.”

Riding the RD
Time marches on. Reviewing the RD350B in 1975, motorcycle magazines universally praised the bike’s broad powerband, powerful brakes and stable handling. In the context of small 2-stroke bikes of the day, I’m sure their praise was warranted. But compared to modern sport motorcycles, the RD350 feels strange indeed.

Perched on the narrow seat, the rider very much sits on top of the bike rather than simply on it. The controls feel oddly vague and remote, while the powerband is quite narrow, with limited grunt below 5,000rpm — and it’s all done at 7,500rpm — although there’s a tremendous rush between the two points on the rev band. Handling on the period tires feels skittish, and braking, while competent, is certainly not noteworthy.

Where the RD350 scores, though, is the fun factor. My fellow tester compared the experience to being dropped into a scene from the retro-TV show Life on Mars and reliving the 1970s — disco mirror balls, platform soles, Afro hair and all. In an age of cookie-cutter, plastic-wrapped 4-strokes, the RD’s vibrant paint, sparkling chrome, ring-a-ding exhaust note and trails of blue smoke certainly stand out.

Now what would be really interesting is a side-by-side test with the other 1/3-liter strokers of the day, like the Kawasaki KH400 and Suzuki GT380. And Ian has a KH in his garage, too … MC

Resources
The Yamaha RD/RZ Motorcycle Home Page
Yamaha Aircooled RD Club
Parts
www.yamatopdog.com 

Read more about the motorcycles mentioned in this article:
The History of the Yamaha YM-1
Yamaha R5 350 Twin 


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Post a comment below.

 

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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