Cycle News - Archive Issues - 1990's

RACERJEST Michael Doohan's Honda NSR500 It') 0\ 0\ ~ 00 I-< Q) ~ ~ z 18 performance that Doohan debuted in the Catalunya GP a year ago; and the Showa semiactive electronically programmable rear suspension that Criville has been using on and off for the past year, but has now cast aside in favor of a conventional rear shock. "We achieved the same level of performance and rider control with fuelinjection as with carburetors," says Hattori. "But we could not obtain any additional performance, so for the time being we have put this to one side, though our research will be valuable for future twostroke applications (like an NSRSOO roadster, eh, Hattori-san?). Mr. Criville used the electronic rear shock to adjust the suspension to his liking last season, but now he prefers to keep the same setting throughout a race, and Honda did not push him to use it. The electronic suspension is only ari additional factor to be used at the rider's option. His choice: Mick-san never used it ("One more thing to go wrong," was the reason he gave us). And we preferred not to pursue further development of the water injection, because of the weight penalty, which is more than 6 kilograms (12 pounds) at the start of a race. Instead, we developed a new electronics system aimed at achieving the same result without adding greatly to the weigh t." Weight is a factor with the NSR500, hence the magnesium crankcases fitted to the Doohan bike I rode, which allow it to scale close to the 130kg (286-pound) weight limit. The aluminum cases fitted to the other NSR riders' bikes add almost seven pounds to that figure'. . "The magriesium crankcases are less stiff, which can cause the crankshaft to twist and bring problems with conrods," says Hattori. "Also, we must replace them every two to three races, whereas the aluminum ones last four times longer, so for reasons of budget as well as reliability, we prefer to concentrate on aluminum cases in the future." That's one reason that all four exhaust pipes are now titanium, rather than only the top two like last year. But developing a new electronics package to yield the same improvement in midrange power and ridability, without the extra weight of the water injection system, was a big step forward and presumably accounts for the roadster-like behavior of the single-crank, lI2-degree, V-four engine, wmch otherwise is little changed from last year: Minor improvements in porting and ignition have added an extra 3-4 bhp, bringing the output to over 190 bhp at 12,500 rpm for the first time. But it's the improved pickup from 8000 to 9000 rpm or so that you really notice: There's no jerk when you get on the gas again to exit a turn, and the already meaty midrange power delivery has been made, well, T-bone sized. The completely new carburetors Kei!Un developed for this season are part of the equation: Still a 36mm, dual-body ty,pe, they have a completely different internal design with different valving aimed at improved response from a closed throttle. The new electronics system combines a prograJ:!lffillble RC valve for the exhaust (still with a sensor on one of the carbs to monitor slide position) with the ignition curve and engine speed to deliver the same variable response but in programmable form, so you can choose a different option for a wet track, or a track like Rio de Janeiro without much grip. This gives Honda improved control over engine behavior in the vital midrange that Mick Doohan focuses on. By following his advice and changing up at just over 12,000 rpm, I was able to (Left) The exhausts are made of titanium. The water· Injection system tested early In the season was abandoned because of Its weight penatly. crew and engineers, there's obviously a sincere desire for one or more teams to start pushing them harder - a race like Argentina, where Doohan had to ride through the pack to win, gives a greater buzz than an. easy victory. There's no doubt that Honda's decision to develop a V-twin 500 for the privateer market is partly aimed at stimulating their capable engineers with a new challenge. The only problem is, it'll have to compete against the NSR500, with Doohan riding the V-four. Now that's a chalIen~. appreciate that. Sure, the Honda has heaps of top-end power, but it's that mega midrange that propels you out of the turn as if you had a rocket strapped to your back. Now accustomed to a speed slUfter on my own race bikes, as well as most of the other ones I test, it was a surprise to find that Honda still doesn't fit one to the NSRSOO. Okada's NSR2S0 I rode the same day had one. "Frankly, it's not good for the gearbox and we did have problems when we tried one out," says Jerry Burgess. "But Mick's technique is so good, he doesn't really need it. Our telemetry shows us he closes the throttle only five percent to change gear, compared to other riders' 30 percent, but he's still kind to the gearbox." Honda did use a primitive form of traction control for starts this season, but this wasn't fitted to the bike I rode. The device retards the ignition in the first two gears off the start line to limit wheelspin, then automatically disengages when third gear is selected. The rider has the option of switching it off altogether via a button on the dash. It might have come in handy for outsprinting the Airfence truck to the next turn, if he'd been going in the same direction on the track as me. Honda has also experimented with a hydraulic clutch, with a softer operation that would give the rider's left hand, which also has to work the thumb brake, an easier time. But that wasn't fitted, either: Instead, it was noticeable that the clutch action on the Doohan bike was lighter than before, thanks to lighter springs being fitted because he is so easy on the clutch. But apart from minor improvements like this, Honda is in danger of running out of development on the NSR5OO: Four years down the line, it's been refined into the nearest thing to perfection on two wheels, a motorcycle so effective and ridable it's effectively competing against itself, as the clean sweep of the first four positions in the Calalunya GP the day before the test showed. Nothing succeeds like success, but talking to Honda pit ~ (Right) New Brembo carbon brakes work at a lower temperature than In the past, and so offer better feel, without a sacrifice in outright power. HONDA NSR500 "'4' WaI8fOlOl8d, 112-degr8e V..four, aankl:ase IllIld vaJve. ~ wllh computerized eIectJonIc power valve DlmelIIions 54 x 54.5mm CIpIclty : 499cc Output Over 190 bhp al12,500 IJlIR {at ge&Jtlox) CIrbInlIan 4 xCUll ~ 36 nvn Keihin will electIOI it powBr YIIIve SIlIlSOr IgnIlIon ................•.................... PI8prognIIllnabIe compuIllrized eIednJnic COl ~ &-speed extradIlbIe CIutdI MuItiplaIe dry alIIIiI ExIrudecI-aIumi twin-spar lnlme wllh faIllical8d swingarm and steeri'Ig-head pNols SutpenIIon Front........•......•....... 43 mm Showa irMll1ed lBIescopic forks with C8Jb0n..llber sliders ReIr FlIbricaIrlckIum swingalm will Pro Unk rising-IaIe linkage and Showa shock wMh IIlanium spIilg Held 22.5 degnles TraI 95nm . . .Ire 1Gna1 1fIWlt 2118.2 pounds dry (as tIlIt8d) WIIghI dIIItIlbulIan : 55145% EngIne .... FNnt AIIr _ 2 x__ a.mboCllban diIca. tour ar.nbo~ 1 X, _ HAC atl~ It8el dI8c wlIIl1Wo-pfllllA HFIC ~ ~ FNnt , '_'7 Mldllllllladal an 3.5D in., HFIC wbIlII ....................................... 181&717 IId"'ualllCll &.00 In., HAC wIlIIIl '1_,,_., 0iIIr 195. Top 0- 1 •••• ; - _ HrlndlRlcill Cocp _ .. SIIIaIII.. . .

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