YAMAHA RD 350 YPVS

It might have produced less than 50bhp and had a top speed of not much more than 100mph, but for many riders Yamaha's brilliantly raw, racy R350LC was the high performance bike of the 1980's - or any other decade, come to that. Certainly, few machines can have brought so much fast and furious enjoyment to so many people, so cheaply, as the liquid cooled two-stroke twin that Yamaha unleashed in 1981.

The LC's pedigree was impeccable, as it was a descendant of the the string of outstanding air-cooled strokers with which Yamaha established an unmatched reputation for middleweight performance. Models such as the YR5, RD350 and RD400 had kept the tuning-fork logo to the fore through the 1970's, while on the race track Yamaha's all conquering air-cooled twins had been superseded by the liquid-cooled TZ250 and 350, with equally spectacular results.

For all the Race Developed nature of this latest in the RD series, the LC's 347cc engine owed more to that of the RD400 roadster than to the TZ350 racer. The water jacket maintained a constant temperature and allowed the engine to be in a higher state of tune without loss of reliability. Liquid cooling also helped make the 47bhp motor cleaner and quieter than its air-cooled predecessor, important for environmental reasons although not enough to satisfy US emissions regulations.

The LC's other race- developed feature was its cantilever rear suspension system, which featured a single shock mounted diagonally under the seat, instead of the RD400's twin shocks. Chassis layout was otherwise conventional, with a twin-downtube steel frame, slightly raised handlebars, attractively rounded styling and a twin-disc front brake.

One ride was enough to get most speed-happy motorcyclists addicted to the Yamaha's exuberant performance. Below 6000rpm it was ordinary; starting easily (with a kick), idling reliably and feeling docile. Then the motor came to life with a scream through its twin pipes, and a burst of acceleration that was as thrilling as it was sudden. With its riders chin on the tank the LC was good for 110mph, but it was the fierce way it got there that made the bike so special.

The Yamaha handled, too. Its forks were slightly soft, particularly when the powerful front brake was used hard, and the front end could feel decidedly twitchy when the bike was accelerating hard out of a bend. But the frame was strong, the rear suspension worked well and the LC could be flicked around with the ease and precision of a race-bred machine weighing just 150kg with fuel.

The LC's speed and fire were brought to a wider British audience by the spectacular RD350 Pro-Am series. The main attractions were that prize money was good; riders were aged under 25 (some professionals and some amateurs, hence the title); and the LC's were identical, prepared by Yamaha and allocated after keys were drawn out of a hat. The result was close, aggressive racing that saw the first year's title appropriately won by a rider named Wild, and brought future Grand Prix stars including Niall Mackenzie to prominence. The format spread, and led to an international 350LC series that was equally hotly contested.

All in all the RD350LC was a magical motorbike: fast, reliable (when standard), agile, reasonably practical, tuneable, raceable, and most of all fun. Over the years it was updated several times, notably in 1983 to produce the RD350 YPVS, whose exhaust power valve added midrange power; and three years later with a full fairing to create the RD350F2. All shared the same key assets: irresistible performance and value for money.

QUICK SPECIFICATION - YAMAHA RD350LC (1981)

Engine Liquid-cooled, two-stroke parallel twin
Capacity 347cc (64x54mm)
Maximum Power 47bhp @ 8 500rpm
Transmission Six-speed, chain final drive
Frame Steel twin down tube
Suspension Telescopic front; monoshock rear
Brakes Twin discs front; drum rear
Weight 141Kg
Top Speed 110mph

This was the first bike I bought after passing my test. What a machine. Pure lunacy and Legal to boot. This is the one bike I recommend everyone to have a play on before they are too old to.

This was a twin cylinder, water-cooled 2-stroke engine, which featured Yamaha's innovative "YPVS" . "YPVS" stood for, Yamaha Power Valve System, and is now used in nearly all 2-stroke engine design. The system was designed to vary the exhaust port aperture, depending upon the revs of the engine. This meant that at low revs, the aperture would be reduced to increase the pressure through the exhaust port, and hence boost power, and when the engine was working at it's hardest, i.e. when the revs were high, the aperture would increase allowing the exhaust gas to flow more smoothly when expelled from the engine.

The exhaust port aperture was varied by using a cylindrical, servo operated valve, sitting just above the exhaust port. This would rotate depending upon engine revs, and give the desired aperture.

The frame that encased this wondrous, but fickle, engine, was not as well developed as it could have been. In fact Yamaha essentially used what was left over from the RD 350 LC production run, to equip the engine with some running gear. Changes were made to the chassis over the next few years, but it still never got the frame that it deserved, and because of this, the "Power Valve" got a reputation for being a bit of a handful when it came to handling.

There have been many examples of this bike which have undergone some radical and some not so radical changes, at the owners expense, to produce the total package that Yamaha should have first produced. The most common of these, was the mating of the Suzuki "Gamma" frame and "Power Valve" engine.

Below are my only remaining photos of my Power Valve, not very good quality either, as it was stolen from me just 10 months or so after I got it. Those were the most frantic 10 months of my motorcycling life, and remember, if someone offers you a go, bite their hand off.

Head on view, with Powerbronze fairing fittedSide view, with Powerbronze fairing fitted

For a bigger image size, just click the thumbnail you want


Last updated October, 2005
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