Great Bikes of the 70's: Yamaha RD350

The guy at the bar looked dazed, staring out of the 1975 Yamaha RD350 ad with bitter embarrassment. The copywriter's headline served up a little back-handed solace to wash down with that last swallow of beer from the mug in his hand. "Don't feel bad. You're not the first 750 rider to get blown off by a Yamaha 350."

Anybody old enough to read a bike magazine back in '75 knew it was true.

Return with us now to the blissful ignorance of pre-politically correct, mid-'70s America. Before we had any clue about the myriad dangers of triple cheeseburgers, saturated fat, unburned hydrocarbons and street-going two-strokes, there was the RD350. Dirty, foul-mouthed, deliciously quick and relatively affordable, it was (is?) a Giant Killer for the ages.

From the first '73 RD350 to the last 1975 RD350B, Yamaha's overachieving pocket rocket humiliated triples and fours packing over twice its 347ccs on racetracks and backroads all over the planet. Back when bell-bottoms were cool and Harley's weren't, most anybody's big-bore multi roasted the RD in a straight line. Horsepower was cheap, and any fool could twist a throttle.

But motorcycle handling was still an oxymoron in Japan...except at Yamaha. When seventh-morning services convened at the shrine of the divine apex, street or track, all bowed to the RD. For the proletarian canyon commando, laying down $3000-plus for one of 50 1974 750SS Ducatis was like Led Zeppelin playing the next freshman/sophomore mixer: very bitchin', and highly unlikely. Kawasaki's very fast, very large Z-1 wore a $1995 price tag. But a 1974 RD350 sold for $908: Moet Chandon on a Schlitz budget. Racetrack handling for the masses.

No surprise there. Look up production racer in the dictionary and it says "...see Yamaha." Or at least it should; nobody before or since has built a more accessible, successful roadracing tool available to J.Q. Public.

The RD350's street roots stretch back to February 1967, and the YR1--Yamaha's first street-legal 350. But the 1970 R5 350 drew a straight line from brand Y's TR production racers to the street.

Fast forward from the YR1 to the mercifully cleaner lines of the 1970 R5 350. Adding new seven-port, reed-valve cylinders and a few other refinements turned the '72 R5C into the 1973 RD350. Now we're on to something. Even in '73, RD styling was still parked somewhere between tawdry and garish. But 0.010-inch thick spring steel reed valves between 28mm carburetors and the new, seven-port cylinders made all the difference. The 347cc RD twin used classical 64x54 bore and stroke numbers to spin out about 35 horses at 7500 rpm.

Pushing 352 pounds fully fueled, Motorcyclist's admittedly rough-running 1973 test bike covered the quarter-mile in 14.48 seconds at 89.8 mph. Cycle magazine's RD ran closer to its potential with a 14.12-second/93.2-mph blast. Those numbers were underwhelming alongside beasts like Kawasaki's 12-second triples and fours. You could fluster 'Vettes and Hemi 'Cudas roosting away from a light, but the RD wasn't a dragster.

Agile, light, simple and reliable (see "Yamaha RD350/RD400: Charting the Changes" sidebar, p. 64), the RD would take you from work and back Monday through Friday with Clark Kent gentility, offering only the odd oil-fouled B8HS spark plug in protest. It was smooth and comfy enough for freeway travel, allowing gas station pit stops at 100-mile intervals; the thirsty little twin's 3.2-gallon fuel tank called up reserve every 70 miles. Two quarts of oil flowed through the Autolube system every 500 miles or so. But turn up the volume and fuel mileage fit the bike's Bad Boy image. Figure about 26 miles to the gallon if you were loose with the loud handle.

Back when gas and thrills were cheap, the RD's minimalist approach was more suited to eating up twisty pavement than straight stretches. The engine and frame were what made corner-carvers nuts. Both were born on the racetrack, derived from the 750-slaying TR2 production racer's heart and bones. The streetbike's frame used thicker-wall steel tubing, but the geometry was track-spec. Aside from details like a dry clutch and a longer transmission input shaft, the '73 RD350's cases and crankshaft were effectively identical to the liquid-cooled '73 TZ350 (which was basically a liquid-cooled version of the familiar TR350 Don Vesco used to win the 1972 Daytona 200 ahead of two other TR Yamahas).

From its birth until Yamaha's FZR400 took over in 1988, the 350 Yamaha two-strokes were pretty much the dominant tool for 400-class production racing on the cheap. San Francisco Bay area RD aficionado Dale Alexander remembers the 350 as a potent, reliable tool once it was set up correctly. "I could race my RD all season for the price of a new FZR400," he says. Before moving on to TZ Yamahas, Formula 1 Suzukis and such, Thousand Oaks, California's Thad Wolff routinely clobbered all comers in the 1979 AFM 400 production title aboard a very rapid RD375 (extra displacement courtesy of TZ750 pistons in chromed bores, spinning a TZ250 crankshaft). "The only competition for a well-set-up RD was another RD," Wolff remembers.

In the hands of guys like racer/tuner/team owner/internal-combustion mastermind Don Vesco (the man went 251.924 mph on the Bonneville salt in an 18-foot-long streamliner motivated by twin TR2 350cc racing engines in 1970), relatively cheap, interchangeable TR/TZ parts made RD Yamahas the production racing force to be reckoned with--on (or off) the cheap.

After swapping the stock exhaust for expansion chambers, raising the exhaust ports, opening the intakes, widening the boost ports, slipping a 5/8-inch spacer between the reed valve block and the cylinders (breathing room, baby...), swapping out the stock 28mm carbs and maybe single-ring pistons, milling the heads for more compression and maybe adding slotted connecting rods, a full-house RD made 50-plus horsepower. "You could make 'em run almost as quick as a TZ with all the good stuff," Vesco says.

Even without all the good stuff, nothing got through a tight set of corners any quicker than a savvy RD pilot. Motorcyclist's November 1974 test of the RD350B said, "...in everything but all-out acceleration, the Yamaha 350 will probably outperform just about anything on the market in box-stock trim." We griped about hard grips, a little too much engine vibration and footpeg mounts that eroded rapidly at maximum lean. Otherwise, the RD was a gem.

Despite an "incontinent" Autolube oil-injection pump, excessive intake honk and a grabby clutch, Cycle magazine was equally enamored of its first RD test bike. Brakes? The 10.5-inch front disc and rear drum proved to be the most potent braking system Cycle had tested. "The little 350 generates enough decelerative force to jerk your eyeballs out--and it does it without a lot of lever pressure," saideth Cycle's stone tablets. What about handling? The words came down from Cycle's Westlake Village stronghold in a flurry of granite chips: "...the bike can burn through switchbacks and carve around sweepers like few in its displacement class and few in any other class."

Even a pristine example of the breed (like the 1975 RD350C pictured) will underwhelm derrieres calibrated to current four-stroke sporting weaponry. Still, novelties like really light weight and the two-stroke's rush of dirty little explosions every time a piston heads earthward ("Dang the ozone layer, Scotty, give me acceleration!"). Eco issues aside, it's a deceptively quick little beast to ride.

The RD looks tiny by 1996 standards because it is. Even so, nice flat bars and a seat to match keep six-footers comfy for 100 miles or so between fuel stops. Twenty-year-old suspension bits feel...well, about 20 years old. The little 350 still corners on rails, even if it does wallow and grind its low-slung undercarriage at relatively mild lean angles. But keep rowing the cliche-smooth transmission's six tightly bunched ratios to keep the hydrocarbons burning between 6000 and 8000 rpm and the RD flat out roosts--60 mph arrives in less than four seconds. Even through the tastefully muted stock mufflers, the weed-whacker-on-benzedrine exhaust note is pure heaven.

Careful, though--some things never change. Since most of its 352 pounds rest on the rear wheel, the 350's front hoop enjoys pointing out interesting cloud formations under full throttle. The Habitually Dim still risk wearing it as a hat in the first two gears.

The RD was the official bike of working-class curvy road cognoscenti in the mid-'70s. As Yamaha product planner Ed Burke says, "The RD was a cult bike if there ever was one." All it took to initiate membership was that velvet shriek rising into your Bell Star. Once you knew what it could do to a perfect road on a perfect morning, nothing else was even close. But all good things must come to an end. Neither the cleaner, more "civilized" 1980 RD400F or the liquid-cooled RZ350 (a story for another day) of 1984 could win the war against progressively faster, more sophisticated heathen four-strokes. Riders demanded bigger, faster bikes. The EPA wanted cleaner ones. The handwriting was on the wall. The RD350 begat the RD400 in 1976, and by the end of 1980 the 400 disappeared from Yamaha showrooms as well.

If the hair on the back of your neck still stands at attention at the sound of a crisp RD, take heart. Plenty of good ones still live under the "Yamaha" section of your local classifieds. For very little money (see "Used RDs" sidebar, p. 70), you can take a trip back to the good old days, when two strokes were better than four. >

For further reading, try Yamaha, by Mick Walker, and Yamaha Racing Motorcycles, both available through Classic Motorbooks, (800) 826-6600.

www.yamaha-motor.com

Yamaha RD350/RD400: Charting the Changes
Evolution of the Beasties

Once Yamaha's 1972 piston-port-fed R5C begat the reed-valved, seven-port RD350 in 1973, very little changed for the next three years. Aside from the obligatory new coat of paint, the big news would have to wait until '76, when Yamaha kicked the rest of the 400 class right where it hurt. Enter the stronger, more civilized RD400.

Engine changes aimed at more power with fewer revs. Thus the 400 got 8mm more stroke, which bumped displacement to 398cc. Stronger coils and a 280-watt generator made for easier starting and fatter sparks under all conditions. New 28mm Mikunis inhaled through a bloody huge airbox.

Sliding the 400's stroked engine 20mm closer to the front wheel reduced its predecessor's wheelie-prone nature. Rubber engine and footpeg mounts made for a smoother ride. The 400's alloy wheels were heavier than the 350's wire hoops. A new-for-'76 rear disc dialed up brain-warping stops and improved suspenders were more composed over all manner of bumps for a more comfortable ride.

The 400's seat was thicker and more comfortable as well. Turn signals were self-canceling, the engine fairly sipped two-stroke oil (thanks to a more accurate Autolube injection pump) and the slab-sided fuel tank carried a quarter-gallon more combustible fluid than the 350's.

The bigger twin made a couple of extra horses at 7000 rpm, but all that extra civility bumped wet weight to 378 pounds. The 400's poundage and taller gearing had it running low 14-second quarter-miles at about 95 mph. Still, it wouldn't smoke out of the hole like a 350.

From there, the graphics changed in '77. In 1978 the 400 grew a nifty tailsection and a coat of silver paint. The 1979 RD400F, a.k.a. the Daytona Special, arrived with blood-red-on-pearl-white paint and throttle-controlled butterfly valves in its exhaust headers to squelch exhaust effluvia. Unfortunately, they also squelched horsepower. At least the ground-fouling foot brackets were replaced by less invasive bits.

The Daytona Special was the end of the trail for air-cooled RD Yamahas. Liquid-cooled, catalyzed-for-your-protection RZ350s relit the lamp in 1985. But it went out a year later with the last 1986 RZ. Is the light that once shone so brightly dark forever? Can technology bring them back? Both good questions, ones that just might be answered by the likes of Bimota and Honda in the next few years.--T.C.