When set up correctly any “Valve” can be a pleasure to both own and ride with more than adequate brakes and chassis for the speeds involved, while keeping the 50 plus horses in check at all times. Keeping on top of the little engine can mean no more than putting good quality two stroke oil in it, and regularly balancing the carbs, although a fresh set of rings every now and then really gets one to perk up a bit.
Quite surprising to more modern day riders is the relatively narrow tyres ability to hang on for dear life when deep in a bend, proof that size isn’t everything, this is backed up by the hordes of vintage and classic race bikes that run similar size rubber to the RD at race speeds quite easily. The temptation to fit over size rubber especially to the rear should be resisted at all cost as the handling suffers terribly if the accepted width is ignored, the standard 110/ 80 section is perfectly adequate although Bridgestone have satisfactorily tested the 120/80 BT45 on the RD and do actually recommend it now as a rear fitment for the earlier YPVS version.
When ridden fast the power valve is not a machine for the faint hearted as the chassis doesn’t enjoy trailing the throttle when entering any corner, so a fair level of commitment is needed to tighten the whole lot up and get the most out of the bike. Once on the gas the front end is accurate and true while the engine chimes in and pulls the rear around neatly. Like wise if the brakes are dragged well into a corner the front tyre grabs tenaciously so it would appear the whole lot up front needs to be kept busy rather than just idling around. This is the result of indifferent damping and springing and a direct by-product of copying the TZ forks that performed exactly like that throughout their time in top class racing. The Brazilian version is certainly not improved and if anything is worsened as the springs loose their fight quite early on in life, a set of after market bouncy bits, Hagons do a fine set, will sort a tired out front end, along with some fresh oil, giving it a completely new lease of life. The rear shock is perhaps the one failing on the original design with the brand new stiffness soon deteriorating within a short period, becoming the spongy and less authoritative example seen on most PV’s, this can be easily remedied with either a rebuild of the original item, a new after market unit or the one off the F2 which appears to be a better bet. The Brazilian model has not been granted the update to a better version of damper so expect the back end to be on a par with a belly dancers butt on payday after a few thousand miles.
The Power valve engine doesn’t feel all that powerful when directly compared to the older RD’s and LC’s, despite surpassing all that came before it in the horse power and torque stakes, as the combined effects of the reed valve intake and power valve exhaust ports serve to soften the usual intense two stroke kick making the power band more of a gentle rush to proceedings. The four stroke like power delivery opened up the world of the two stroke to a wider audience back in 1983 an most who sampled the power valve for themselves couldn’t fail to be left impressed by the twin cylinders engine characteristics. Around the mid eighties there were many an LCII owners girlfriend who certainly appreciated the softer power delivery. A more laid back approach can also be taken with the gear pedal when just cruising around and there is no real need to keep the motor buzzing as on the earlier models. Even so things start to happen pretty quickly once up above the seven mark on the tacho as the YPVS exhaust system becomes over ridden and the engine starts to feel just like a standard LC, the scenery begins to get all blurry out the corners of your eyes, and the whole bike simply come alive with two stroke happiness. Within seconds the six speed gearbox is all used up and both the speedo and tacho needles are bending off their respective stops with nowhere left for them to go.
We didn’t have much in the way of accurate dyno’s back in the early eighties but we now know that on a good and well maintained example torque builds up seriously around the five grand sector of the tacho while the horsepower reaches its peak at 8,500 rpm before tailing off to virtually nothing worth having, save a scream in the ear, a thousand later. Some LC owners have claimed to hold on a long as 10,500 rpm but this is the cause of many a crank failure as the big end cage is not capable of reliably maintaining these figures and any dyno sheet will accurately show the engine gave up any hope of increasing the power output long before. A well set up “Valve” can show a clean pair of heals to most machines under the right conditions particularly if you do have a good look at the way the torque and power curves peak and the gears are shifted accordingly without over rev. Any overrev is about as good as standing still when it comes to the accelerating game, so give the lever on the left a quick prod and get another ratio working for its living.
As far as maintenance goes the engine is generally very good and hardy, especially when left in standard or very near original specification. RD350’s have been seen with 40k on the clock and still on the same bore size. The cylinders are the old type iron lined affairs and this means that up to ten rebores can be carried out from new and the relevant sizes of piston be fitted giving effectively 400,000 miles if well looked after even then the barrels can be easily re lined back down to the standard 64mm bore size ready to start off again! This re lining can be carried out almost endless so providing the parts are still available the good old RD/LC should still be around for a while yet. The pattern parts people love the RD/LC set up and virtually every reciprocating part and gasket is available as a cheaper alternative part to the genuine version. Clutch parts and baskets are also readily available as is every seal and o ring making engine repairs no great expense to carry out properly. Unfortunately this hasn’t stretched to pinions and other gearbox parts but these are generally tough cookies and can last a lifetime if not unnecessarily abused.
RD350R YPVS Time Line
The RD first appeared in air cooled format in 1973, looks wise it had moved on little from its predecessor the piston ported R5 and YDS7, and ran almost unchanged albeit a few cosmetic touches for the next seven years. There was little in the way of power improvements with the 30bhp 250, while the 38bhp 350 grew into the long stroke RD400, kicking out just over 40bhp. The radical LC emerged as a result of the super light and fast Suzuki X7 and, even though the PR and AD men claimed a direct link between the TZ race bikes and the latest Yam, the differences were greater than the general public could ever imagine.
By 1983 the LC had been surpassed by the more technically advanced YPVS. Yamaha hadn’t actually taken any chances with the new bike however sharing as it did many components and design details with the first LC and in turn the early RD’s, but the top end of the engine was where it was all at with the electronically operated rotating exhaust valves that gave a much wider, four stroke like, spread of power. A 250 version was advertised alongside the larger model during 1983 but was never officially imported into the UK by Mitsui Yamaha, although some continental countries did get it, as well as the Far East and Australia.
The YPVS saw a few purely cosmetic changes throughout its life with the original bikini faired version making way for both naked and fully faired variants. Mechanically the type stayed true to the original, all the way through the production run. The TZR 250 did carry on the embodiment of the early YPVS, but the miniature engine was a completely fresh design with more in common, parts wise, with the RD500LC than the 350 twin.
The end of Japanese production in 1992 saw the type re hashed and manufactured in Brazil, all parts still fit but as previously mentioned build quality leaves a bit to be desired, especially if the bike has seen a few UK winters.
Had the 350 cc grand prix class not been discontinued then without doubt we would have seen some fine V twin or even multi cylinder RD’s filter down in to the dealers showrooms in later years, especially as the 500 class diminished around the late eighties and early nineties and a few small bikes grew in capacity to fill some gaps on the grids. As it is however the whole RD dynasty ended with the 1983 YPVS and now is long gone never to return.
RD350R PYVS Specifications
Engine – liquid cooled twin cylinder reed valve induction electronic power valve
Capacity – 347cc
Bore & stroke – 64mm x 54mm
Power – 59bhp @ 9000 rpm
Torque – 36.2ft lb @ 9000rpm
Carbs – 26 mm power jet Mikuni
Transmission – 6-speed wet clutch chain final drive
Chassis – Steel frame twin loop
Suspension – 35mm telescopic air assisted. Yamaha rising rate rear
Brakes – 2 x 267mm disc twin piston calipers. 267mm twin piston caliper
Wheels – 90/90 x 18 110/80 x 18
Weight – 155 kgs
Top speed – 120mph
Wheelbase – 1385mm
Fuel capacity – 17ltrs
Yamaha RD350R YPVS Gallery
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