Retrospective: Yamaha RD350: 1973-1975

(This Retrospective article was published in the August 2008 issue of Rider.)

STORY AND PHOTOGRAPHY BY CLEMENT SALVADORI

Nicknames can be good, flattering, positive…or quite the opposite. In the case of Yamaha’s RD series, the Chef Boy-Ar-Dee moniker—say it slow—was greeted with less than enthusiasm by the company execs in California. After all, that RD was meant to stand for Race Developed, not a can of Americanized overcooked pasta. Grin and bear it.

The Chef Boy 350 was an updating of the venerable R5, a mainstay of the company’s line. In this day of 100-horsepower 600cc sportbikes it takes some mental acuity to go back to when a 350 was considered a two-wheeled weapon of consequence. Kawasaki had come out with its 350 triple, the Suzuki GT380 was no slouch in the performance department, and Yamaha wanted some of that market.

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In the middle ‘70s the company had a split personality with its street models, seeing the EPA’s handwriting on the wall: Two-strokes would not be forever. With this understanding Yamaha’s major focus was on the four-stroke TX series—500, 650 and 750 twins, less advertising for the smaller, definitely cheaper two-stroke twins. The 1973 price for the RD350 was $839, while the TX500 came in at $1,350.

The RD350 was essentially a reworked R5 350, with identical 64mm bore and short 54mm stroke and 28mm carbs, sitting in a cradle-type tubular frame. Yamaha’s reliable Autolube oil-injection system had a tank holding more than half a gallon of oil, good for a long run. What, then, was new with this Chef Boy 350? Quite a bit. The engineers had taken the R5’s engine and put in seven ports and reed-valve induction…called Torque Induction by the ad guys. For those who have never been familiar with two-strokes, the reed valve—a success on Yamaha’s single-cylinder motocrossers—was a bit of high-tech sophistication, using a very light, very thin, very flexible piece of metal between the carburetors and the cylinders that would open when there was any vacuum within the engine caused by the exhaust gases flowing out, allowing the air/oil/gas mixture in. It closed when the pressures were equal, preventing any possibility of the fuel getting shoved back out the carburetors, or “blow-back,” as Yamaha liked to call it. Add that to multiple ports, with half-a-dozen allowing for normal intake and exhaust work. The seventh port threw in an extra hit of fresh mixture at the last micro-second that served to cool the piston dome, as when the fuel went in through the crankcase it warmed up as it flowed to the combustion chamber. All a bit confusing to the four-stroke mind, where we think of valves rather than ports.

1974 Yamaha RD350.
1974 Yamaha RD350.

What this did was add a little more power in an ever-narrower powerband. Horsepower and reality were at odds, with Yamaha immodestly claiming 39 mustangs at the crankshaft. However, when the unromantic editors at Cycle magazine had the temerity to put the RD350 on a dyno, they found only 30 thoroughbreds at the rear wheel. In truth, 30 horsepower out of a 350 was not bad, but these came on at 8,000 rpm, and at 6,000 rpm the number dropped to 20; keeping those 20 to 30 horses at full gallop meant doing a lot of shifting, so Yamaha added a sixth gear to the transmission.

The engine work made it a little more finicky to ride, but really more fun. You could set the tach at 5,500 in sixth gear and cruise at 70 mph, or keep the engine on the boil and howl along the back roads. The bike was weak on torque, but if the rider happened to hit the powerband in first or second gear, that front wheel would reach for the sky. The suspension was a trifle on the soft side, and various bits could drag in the corners if the rider were cheerfully aggressive, but the great advantage was the new 10.5-inch disc brake on the front wheel, with the caliper having two slave cylinders pushing the opposed pucks that ferociously squeezed the disc. Everybody loved the new brake. On the rear was a standard drum. Tires were a 3.00 x 18 on the front, 3.50 x 18 on the back, with 52 inches between the axle centers.

1974 Yamaha RD350.
1974 Yamaha RD350.

Over the headlight was a simple dash, speedo and tach on either side, a key in the middle, two lights indicating turn signals were on, high beam—and a light to tell the rider if the brakelight was not working. The ignition key was also good for unlocking the gas cap, unlocking the saddle, and locking the steering head. Gas on, choke on, key on, kick. No electric starter on this dandy, not that one was needed. It had good manners, and even cold was a two-kick affair. Burble off down the street, out into the countryside, and with the properly warmed engine, screw that throttle down! There was a big noise as the carbs gulped air. The RD weighed 350 pounds with full gas and oil tanks, and a competent lightweight rider could hit 90 mph from a standing start in under 15 seconds.

Hot-rodding this little gem was a growth industry from the moment the Chef Boy appeared, with a great array of bolt-on goodies. Within weeks the café boys could buy a bikini or full-race fairing, light fenders, a bigger gas tank, clip-on handlebars, rear-set footrests and any manner of high-performance expansion-chamber exhaust systems. Aftermarket wheels allowed for wider, low-profile tires. Koni could supply far better shock absorbers. For anyone wanting to get into the engine, the pocketbook was the only limit. If anybody doubted the ability of a two-stroke 350 twin to run, all they had to do was take a ride on Yamaha’s TZ350, a liquid-cooled production racer that put out more than 60 horsepower. The single most popular bike in club racing was the RD350.

1974 Yamaha RD350.
1974 Yamaha RD350.

The Race Developed Ar-Dee stayed on the Yamaha charts for only three years before undergoing considerable changes and becoming the RD400 (Retrospective, October 1991). Not much was altered in those three years other than the MSRP, as the ’75 model cost $1,071, a whopping great 25 percent increase in price over the ’73.

 

1974 Yamaha RD350.
1974 Yamaha RD350.
1974 Yamaha RD350.
1974 Yamaha RD350.

27 COMMENTS

  1. What are your sources?
    The orange and black was the 1975 model year, As I recall the 1974’s were almost identical but were maroon in color.
    I bought my 75 new at Barney’s Motorcycle in St. Petersburg, Florida- March 1975.

    • Our source is the owner of the motorcycle that allowed us to take photos of it. According to your color information, it appears he could be wrong about what year his bike is. We’re looking into it further.

  2. my wife bought me a brand new 1974 yamaha rd350 for a christmas present that year. the color was maroon. i didn’t have a motorcycle licence – and, as a matter of fact, had never driven a motorcycle before !!!

    that little mother could fly! the specs indicate that top speed is 105.6 mph.
    but, i remember one night my wife and i were out cruising – and i looked back and yelled – look at the speedometer, honey – the needle was sitting on 115
    mph !!!
    i loved that bike – i’m even considering buying a restored ’74.

  3. This bike is a 1975 model Yamaha only produced the bike in one color each year 1974 was maroon I think Yamaha called it wild berry.This bike was a very scary ride for a beginner it was really built for racing I could not get the bike home without several wheelies. 115 was very common.

  4. All 1975s were “Portuguese Orange” (the color of shown), and were RD305Bs on the ID sticker, on the headtube. Yamaha cleared the 1975s out, at $899 (there was an ad program with billboards, etc.). I put 28K miles on one, most of it with the right wrist twisted.

  5. The only brand-new motorcycle I ever bought was an orange and black 1975 Yamaha RD350B for $995, just like the one in the article. I bought it from Dave at Yamaha of Columbia on Two Notch Rd in SC.

    It was very quick but mine was not at all reliable as the dealer had failed to put oil in the transmission. I discovered that fact after a few miles. I had to put oil in it to get home and when I called the dealer, he told me that was just too darned bad because I couldn’t prove they had messed up.

    • I have a 1974 rd350 European model which came out with a bigger gas tank for touring and it’s blue stock from the factory

  6. The 30 bhp that you quote in the article is from Cycle’s 1973 test of the then-new RD. They also dyno-tested a 1975 RD-350 (orange tank…like this one) and got 34 bhp.

  7. I had one in Malta when posted to 41 commando it had a green tank 1974 awesome bike all my mates had 750 and bigger they thought bigger was better not on Island of Malta with this bad booty in the saddle

  8. Seems a bit of confusion here re build dates it was common for Yamaha and still is in a lot of countries to release a year model about three quarters into the previous year. So everyone here that said the U.S. spec only Burnt Orange colour was a 1975 model is correct. However the ’75 model was released well before December 1974. Cheers

  9. My 73 wad that Gold color. I was about 14 or 15 when I had it. I had many others before this one sho I was familiar with binge bikes. But, that lil monster would hit the powerband and yep, there goes the front wheel while tha the back wheel would wane to break loose. Kind off a scary quick ride guier a kid…lol

  10. I started my roadracing career on an RD350. “RD” did NOT stand for “Race Developed”, although it certainly should have. Never was a bike more prone to racing available to John Q Public. If you didn’t ride an RD, you might as well stay home. A giant killer for the ages.

  11. (For the US,…) The porteguese orange/black stripe bikes were indeed 1975…..RD350B . The 1974 RD350A was ruby red (purpleish maroon) with a double white pin stripe. The 1973 RD350 was the very pretty brandy red with a white and black graphic. Going back three more years,….the 1972 R5C was mandarin orange/ with black….the 1971 R5B was mandarin orange/ with white…..the 1970 R5 was purple/with white.
    There was a mid-year change/update on the 1975 RD350B…..the same color,…but the carbs received some changes….I believe the jetting was slightly different (leaner) and a very visible change, was the addition of the large boots on top of the carbs, where the cables come in to attach.
    How am I sure of this? I was assembling them, and servicing them then at the dealer level …..

  12. Ah, the rd, I loved that bike…My dad helped me buy it for $500 bucks off an old farmer up the road. I think it may have been a little to explosive for him on the gravel roads. I was 15 at the time, and had been riding a lot of dirt bikes ( RM 465, YZ’s, and Cr’s), so I felt confident.
    I painted a 7 into a 9 on the old blue and white liceience plate, and the next thing I knew I was pulling three gear wheelies, and redlining @ 115mph. She would hold that for miles ( as long as the oil tank was full..!)
    Soon after, expansion chambers and jets made it even better, then I beefed up the clutch springs with washers, now it was amazing…! I beat my brothers 750 Honda ( to 100mph),and he was shocked…me too..!
    I might get another one for my 60th birthday…?, will see. ( and yes, 1974 was maroon/ burgundy…..)

  13. I’m currently looking at buying a 1972 rd350 a. It is imported from the US to England and has undergone a full restoration but not to original, but cafe racer style with JL racing expansion chambers and rear sets etc.
    The price is high…..(£4500) so I’m hesitating. Also, I’m not sure if it’s an R5 or an RD. I’ve asked whether it’s 5 or 6 speed and reed valve but no reply as yet. The bike is immaculate and has done less than 10,000 miles since rebuild.
    Do you guys think it’s a good idea?
    Do you guys think it’s a good idea?

    • It is an rd350a…and I meant to type 1000 miles not 10,000!
      I would love to know how people got on with them? Was the unreliability just fouling up from oil or was it more?
      Parts seem to be relatively easy to get in UK but not researched that much.

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