Eighties Icon: Yamaha RD350LC

Words: Jon Bentman | Photos: Gary D Chapman

At the end of the Seventies, Yamaha took the decision to reconnect the link between their successful racing TZs and their RD road bikes. Combining British design talents with Japanese technology, the resultant LC exceeded all expectations, becoming a bike that changed laws and lives forever. Jon Bentman rides Niall Mackenzie’s mint example.

It’s 1980 and Yamaha’s existing twostroke light-middleweight sports offering is the RD400, by now in its fourth year, as the F model. Good for a steady 106mph, and a fair deal faster once a decent tuner has been at the barrels. Good enough to be spanking everything in proddie racing, but then what opposition does it have?

Suzuki has launched the instantly forgettable GS425 four-stroke twin, Kawasaki is hanging on with the KH400 (once quite a sharp racer, but no more), and Honda had replaced the jewel-like CB400F with the altogether more mundane CB400 Super Dream, no faster than the F, but a lot more dull.

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So, Yamaha had that lightmiddleweight sports category sewn up in 1980, but far from doing nothing, Yamaha instead pushed the whole game clear into the next century. The history books will tell you that at a time when USA legislators were vilifying the two-stroke, with sales there on the wane, Yamaha took the brave step of tasking their newly-formed European design team to come up with a new two-stroke sports model.

That European team had a lot of British bods in it, not least Paul Butler who was Product Planning Manager at Yamaha Europe. Butler had worked with Kenny Roberts in his early GP years and later would be part of the Marlboro Roberts team set up. Today he’s an IRTA boss and race director for MotoGP.

Butler had alongside him another planner in the form of Bob Trigg, pulled from the burning wreckage of Norton Villiers Triumph (NVT), and the services of another Norton refugee, designer Mick Ofield. Bearing in mind the British motorcycle industry had only recently written itself off on the unforgiving crash barrier of bankruptcy, Yamaha did well to locate and put trust in real British talent. So the LC had a surprising amount of British input in its development.

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Unlike that British industry, Yamaha had been learning their lessons over the previous decade. For instance, they were using common-platform engineering, something you hear a lot of today in automotive manufacturing. Already in 1973, when they coalesced their various two-stroke sports cycles into the one RD line, they’d managed to rationalise the models – 125 and 200 on one common base, the 250 and 350 (later the 400) on another.

This would carry on into the LC series, with the 250 and 350LCs sharing nearly all components, save for the larger bore in the barrels (same stroke), the cush drive in the rear wheel and the twin discs on the 350 (and an different master cylinder – but let’s not get too pedantic).

The 1973 RDs had also brought reed valves to the two-stroke market, which Yamaha marketed as ‘Torque Induction’ for the manner in which the valves cleaned up and boosted the low to mid-range, while at the same time allowing more racy cylinder porting, so more top-end, too. The RDs had nonetheless been left behind by the developments in Yamaha’s TZ road racer range.

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Before 1973 there had been strong familial linkages, reaching back into the 1960s when their YD roadsters and TR racers shared a fair deal of common design and componentry. But the 1973 TZ moved the racing game a fair way ahead; that first TZ was watercooled, and by 1976 the TZ had also gained Monoshock rear suspension.

By the end of the 1970s the two model streams were in effect miles apart. So the LC, when it arrived in May (250LC) and June (350LC) 1980, was intended very much to resurrect that racing connection. While the frame was very different, as well as the stylings, the LC’s cylinder barrels and head – all water-cooled – certainly looked very TZ.

The monoshock rear, while different in detail, in as much it sported a much shorter shock absorber, again still successfully mimicked the TZ. And the LC had expansion chamber exhausts. The TZ link was back and this underlined the sporting aspirations of the new models. In 1980 it was cutting-edge for a two stroke road bike; the LC proved to be a game changer of monumental proportions.

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Interestingly, Yamaha reversed the clock somewhat on the engine. The RD400 had grown away from its 250cc sibling by way of increased bore and stroke. But Yamaha returned to their classic architecture with the LC. The 250LC had, as ever, the perfectly square dimensions of 54 x 54mm, while the 350LC, as with the RD350 of 1973 (and all Yamaha TZ350s) was 64 x 54mm – simply the 250 with a bigger bore.

….For the full feature, pick up the February issue of Classic Motorcycle Mechanics. For more information on how to get your hands on a copy, click HERE.

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