Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/146701
GTEST Honda NSR500 ~I By Alan Cathcart Photos by Patrick Gosling t was the Sound of Suzuka that went straight to the top of the 1992 World Championship charts, and stayed there till cruel fate intervened, by targeting the OJ;le weak link in the whole arrangement - man, not machine. Not a hit single, but a fab four, the bike that ushered in a new era of two-stroke racing technology tq the 500cc class: the latest, greatest version of Honda's biggest and best the NSR500 single-crankshaft V-4. For race engineers in rival teams, hearing the dramatically different sound of the NSR500 when untimed practice for the Japanese Grand Prix back in March began must have . represented as much of a milestone in modern GP road racing as Elvis Presley or the Beatles meant to pop music when their early recordings first hit the airwaves. New, fresh-sounding, and so very, very different. But instead of having to wait for record sales to confirm whether new also meant better, the GP world had the answer right there on their trackside stopwatches: better, because faster, and so evidently easier for Honda's Aussie aces Mick Doohan and Wayne Gardner to ride in Suzuka's torrential downpour. on a 16 Instead of the raw-edged shriek of a factory 500 four aiming for the iedline, the new NSR sounded liKe a deeper, gruffer version of its 250cc V-twin kid brother, but with the same, unhurried, lazy-sounding lilt of a four-stroke Ytwin Ducati. Very different. What Honda had apparently done was to alter the firing intervals on their ll2-degree V-4 single-crankshaft crankcase reed-valve engine, to compress the individual firing strokes into a much narrower range - less than 90 degrees, for sure, judging by the way the new engiue sounded more like a super single than a· frantic four. Having all four cylinders firing more closely together gives improved traction, thanks to the uneven power delivery - a fact appreciated by Ducati and Harley-Davidson owners for many years. Indeed, Harley's dirt track dominance in U.S. oval racing with their 45-degree V-twins is commonly held to owe much to this characteristic, enabling the rear wheel to hook up better on a slippery surface. Honda obviously thought so, too - which is why some years ago they rephased the firing order of their 750cc V-twin dirt sled to ape the Harley's good traction out of turnsl Now, more than a decade later, Honda has applied the same dirt track philosophy to as different a bike as you could imagine: the NSR500. Other manufacturers realized at once what Honda had done, and Cagiva probably wasn't the only one to lay hands on an oscilloscope which apparently told them that the "Big Bang" NSR500 motor has all its cylinders firing together within a 66-degree crankshaft rotation. It wasn't even the first time this had been tried on a GP two-stroke - Suzuki engineers had tried the same thing some years ago with the square-four RG500, without any horsepower improvement, at the cost of substantially increased vibration. B.ut Honda, by adding a balance shaft to their single-crank motor, and beefing up the crankcase design (which was still being improved after the start of the season) had cleverly found the key to the secret treasure that has eluded two-stroke race engineers for many decades: how to make a bike that is mega-powerful (Honda claims "over 175 bhp" at 12,5000 rpm for the Big Bang NSR500) put that power down on the track out of turns. On a par with Suzuki's application of rotaryvalve erigine technology to fourcylinder 500cc bikes with the first RG500 back in 1974, and Honda's own intrOduction of the crankcase reedvalve era in 1982 with their NS500 triple, the arrival of the "Big Bang" engine format on the. 1992 NSR500 is one of the most significant steps ever made in the evolution of the two-stroke racing motorcycle. Future development for all manufacturers during the rest of this century will be based on Honda's initiative in this respect. Starting as of the Monday after Suzuka, in fact - for while Honda and Doohan continued to reap their just reward for such original thought by winning the first four 500cc GP races