Cycle News - Archive Issues - 1990's

G TECH e HondaNR750 just outside the points-scoring top 10 places, but his 11th pl ace at Spa the closest the NRSOO woul d ever get to scoring a World Champ ionsh ip poi nt was overshadowed by Spen cer 's maiden GP victory, th e first win for th e NS500 two-stroke. Even Hond a couldn' t a lter the truth of time. Wh at they could do was to build on the legacy of the NRSOO, which did not race again after H aslam 's 15th place in the 1982 British GP. Firstl y, a pro ject bike was assembled and sent on th e sho w circuit, nominall y th e ultimate versio n of the NRSOO but in reality a sho wcase for Honda's use of advan ced technol ogy and materi als, incl uding a car bon fiber chassis and o ther components . But in Nove mber '8.'1, work bega n o n th e NR250 Turbo, to see if such a machin e could be competi tiv e under th e FIM rul es perm itting turbocharged engines in the 500cc class with a 50% capacity handicap. It was the heyda y of FI car racing's turbo era, with over 1000 bhp obtainable in q ua lifying form fro m l500cc turbo engines, incl udi ng Honda's, and the decision to experiment with some of this techno logy on the N R was irresi stible. Th ere a re obvi ously two ways to cut a go-degr ee V-4 in half, and Honda tried it both ways, firstl y producing a parallel twin 250 wh ich started tests in January '84, then in July a V-twin version. Both In 1980, Japan's Takazumi Katayama finished 15th in the British GP, giving the NRSOO its first-ever race finish, =- - - - - - - - - - - - - - -==== In 1981, the 18 ~ featwed a new engine, dub bed the 2X; it won a race in Japan. employed the same (93.4x41) x 36 mm dimensions of the NRSOO, had twin IHI turbos and originally used carburetors, later replaced with fuel injection - surprisingly, this was the first time EFI was employed on the oval piston engine. By the end of the year , the parallel twin proved to be the most powerful, delivering a remarkable 153 bhp at 20,000 rpm, but only at some cost, Turbo lag was a constant problem, plus power delivery was very fierce and taming the result had it ever been fitted into a chassis would probably give new meaning to th e term rear wheel steering. But the biggest problem of all was heat - vast amounts of it which took a massive network of intercoolers and radiators to reduce, in tu m adding such bulk and weight that it negated the wh ol e advantage of an ultra-powerful 250cc twin. Nice try .but no cigar: early in 1985, th e tu rbo project was terminated. Instead, Honda turned their attention to an altogether different kind of motorcycle - a 750cc oval-piston machine, code -named the NZO. Work on this commenced in March 1985 with the first prototype completed in December of that year. Testing ' and development continued throughout '86, with a B:type version of the and again in the race before it retired after three hours with an engine problem later attributed to human erro r. Surprisingly, the engine was running on carbs again, while cylinder a ng le h ad been further narrowed sligh tly to 85 degrees and camshaft drive moved back to the right side of the engine; otherwise.. th e NZO followed the same 8-valve!I tw in-conrod format as its predecessor; and in due course development yielded 159.7 bhp, with the bike scaling a more-thanrespectable 347.6 pounds in endurance form. Suddenly, people were talking abou t the possibility of a street version of this motorcycle. Wh en Honda took a couple of bikes to Australia for the Swann Series that winter, and Campbell won one of the rounds fair and square on the NR, to place third in the series on his oval -piston 750 behind In 1985, H onda built the NR750 racer, paving the way for the N R750 street bike. (106.9x46) x 42 mm engine achi eving 157 bhp at 15,000 rpm earl y th e following year. The decision was taken to enter the bike in the Le Mans 24 Hour race in April, wh ich with a team of riders led by Australian Malcolm Campbell, the NR750 impressed with a strong second place behind the leading Honda RVF750 in qualifying, the round-piston 1000cc Yamahas of Kevin Magee and Michael Dowson.ut was further confirmation that Honda had in de ed succeed ed in making lemonade out of th e lemon: 'th e Never Ready had ended up showing a New Road for four-s troke motorcycle engine design, one that worked and had finally achieved concrete resu lts. The NR750 street bike is the proof of that: Irimajiri and his team had the last laugh I Honda NR750 technical description n developing th e NR.750 roadster, Honda drew heavy i nsp iratio n from the oval-piston 750cc endu ran ce racer, code-numbered NZO, which appeared a solitary time in the 1987 Le Mans 24 Hours; two 'spri nt' versions, effectively the same bike with a slightly more powerful engine and without lights or a charging system, were later raced in the Swann Series in Australia that same year in the NR's final competitive appearance. Now comes the street version, whose internal Honda designation will cause a wry smile to those eagerly awaiting the upcoming fuel-injected successor to the round-piston ROO Superbike, for the NR750 roadster is indeed the RC401 It is also not intended to be raced, one of many factors behind Honda's decision to limit the power delivery of the NR750 /RC40 in production form to 125 bhp at the most, and even just I()() bhp for several key markets like France and Japan. And to discourage some smart ass from figuring out how to release the 'missing ' 15 bhp and more (H onda admits the engine makes 140 bhp in street-legal form before strangulation), always assuming he can figure out how to tune an ovalpiston motor and re-program the multipoint EFI l em s, Honda will limit production of the NR750 to prevent it ever being capa ble of homologation for Superbike racing. The reason for this is simple, and not altogether altruistic: Honda claims su ch an advantage in engineering terms for the oval piston concept that on an equal basis, it sho uld theoretically outperform any conventional round-piston fo ur-stro ke design of equivalent capacity. That being the case, the advent of an NR750 Superbike would kill that class of racing stone dead, even with the weight handicap I

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