Cycle News - Archive Issues - 1990's

of the 1992 season, their rivals in Italy and Japan worked feverishly to emulate Honda's achievement by adapting the Big Bang theory to their own engine designs. That's when the biggest home truth of all - and the most ironic - became apparent: for years Honda's quirky insistence on sticking to a single-crank "true" V-4 design, rather than a twin-crank motor like their competitors, has drawn persistent criticism from some of their riders and lots of outsiders. The extra bulk and increased gyroscopic effect of the .single crankshaft were supposedly major drawbacks to a design whose main advantage was held to be simply the fact that it was different from all its rivals. True, Honda likes to do it their way - but now they can have the last laugh on all those who predicted it was just a matter of time before they'd have to build a twincrank V-4 like everyone else, or sugg~sted they already had one under development. For though Suzuki, Cagiva and finally Yamaha all tasted success with their revamped 'Big Bang' designs, it was at the cost of a degree of mechanical fragility that the Honda has never experienced. If, as is reported, Yamaha really has decided to do it Honda's way, and have their own single-crank V-4 Big Bang motor under development for 1993, the men at HRC can't be blamed for an inward smile of self-satisfaction. A new page in 500cc two-stroke development has been turned - and it's embossed WIth the letters HRC, just as the 1992 500cc World Manufacturers title is, too. But this is poor reward for Honda losing the most coveted crown of all - the riders title - in spite of winning seven out of the 13 races counting for the 1992 World Championship (five with Doohan, one each for Criville and Gardner); Dpohan's terrible leg injuries suffered in a practice crash at Assen put paid to that - cruel and unusual punishment of a kind that only serves to empQasize how great a role the human factor still plays in GP motor,cycle racing, in contrast to the Formula One car world it now seeks to emulate in the Ecclestone Era. Doohan and Honda were every bit as dominant in the first half of the bike season as Mansell and Williams-Renault were on four wheels - till the Human Factor intervened. No pain, no gain - but too much of one leads to less than you merit of the other! The chance to sample the Big Bang theory in practical form from the hot seat of Doohan's NSR was something to look forward to, so when the summons to Suzuka came in midOctober, I was knocking at the circuit door while the fax line was still hot! And unlike lots of bikes which promise only to deceive, the 1992 NSR500 should-have-been-a-champion not only lived right up to expectations, it exceeded them. Here's how - and why. The big problem about riding works 500 Hondas in the eight successive years I've been fortunate enough to test them has always been what happens when you crack the throttle open as soon as you think it's halfway safe to do so exiting a tum: True, HRC's development in recent years has concentrated on widening the spread of power and smoothing the transition into the strong power band via a . combination of the flap-type 'RCvalve' power valve (latterly controlled by a micro-computer fed by sensors which monitor the tacho needle position and carb slide height), the ignition curve (also in recent years capable of wide alteration by pre-programmed EPROM chip), and exhaust pipe (Above) The 112-degree V-four produces a claimed 175 horsepower at 12,500 rpm. (Left) The engine sits in an extruded aluminum twin-spar frame which features fabricated swingarm and steering head pivots. (Above) The Honda uses 290mm Brembo carbon discs with four-piston calipers. (Left) What is it? Cathcart has no idea, and we have no idea. design. The por,ting on the five transfer/two exhaust port cylinders is also a factor too, of course, in that periodic modifications have, helped raise the power output from the 145 bhp delivered by Freddie Spencer's title-winning NSR500 in 1985, to "over 170 bhp" on Doohan's 1991 bike. But though outright power is obviously vital in terms of blitzing the opposition in a straight line, even Honda - who has traditionally placed more emphasis on this than the other manufacturers in 500cc GP racing - have lately been much more interested in improving engine usability. Hence the ildoPtion two years ago of the 'double strike' (aka 'two-up') engine configuration, with each pair of pistons rising and falling together in a 180-degree layout, rather than firing individually at 90 degrees to each other as befbre. But, however tractab-Ie and easy to ride the NSR500 was low down, the moment of truth inevitably came when you hit the supersport band a~ around 9500 rpm and the engine caught first big time, sending the tachoneedle scudding round the dial to the accom. paniment of a mu££led shriek from the engine. It was a big thrill - unless you happened to be riding the bike on a damp track, when it was mindbogglingly difficult to master. And in the dry - well, even at the comparatively gentle speeds someone like me would ride the bike at, you had to accept that the back wheel had a mind of its own coming out of a turn, and treat the throttle with extreme care. Sure, it was easy to light up the back wheel - only don't get burned doing sol Throttle control was so allimporta~t: not enough, and you lose - but too much, and you crash. You don't even need a full lap of Suzuka to appreciate what a major advance the Big Bang NSR500 represents in user-friendliness - not only for a part-timer like nie, but on a different level, for Mick and Wayne and Alex, too, the traction out of turns is literally unbelievable to anyone who ever rode a works V-4 before - yet you have to pinch yourself mentally to appreciate how potent the bike is you're riding. It doesn't feel so awesomely powerful as it certainly is, because the lazy beat to the engine, coupled with the uncanny lack of vibration thanks to the secondary shaft driving the ignition and waterpump, which acts as a counterbalancer, completely disguises its true nature. A Big Bang motor is actually smoother to ride than the previous Double Strike version - more like the old evenlyspaced firing' order engines. Like its predecessor, the '92 NSR pulls from way down low - 7000 rpm at the expletive-deleted Suzuka chicane, with a practically linear power curve up to and well beyond the 12,500 rpm peak power mark. Not only is the NSR500 motor 'so tractable low .down, it has a massive amount of overrev before the power starts to drop off about 13,500 rpm upwards, making it easy to hold a gear like between the Dunlop Curve and Degner One, to save two unnecessary gear changes. Yet climbing the hill behind the paddock, winding from side to side through left- and righthand turns in third gear at fotir-figure revs, confirms how responsive and tractable the engine is low down. However, it's not till you get somewhere like Degner Two or the exit from the Spoon Curve that you realize just what an advance the new NSR represents. Instead of feeding in the power nervously on the old bike, and hoping to catch the inevitable slide okay when it comes, after a handful of laps on the Big Bang bike, you can actually start to kid yourself you could keep up with Mick Doohan - well, we can all dream ... The bike will accept more throttle much earlier, because assuming the Big Bang firing space is 66 degrees as Cagiva says (another team says 72 degrees: maybe they need to retune their oscilloscope?I), that leaves 294 degrees of crankshaft rotation when the engine isn't doing anything. this precious breathing space gives the rear tire a chance to find some muchneeded grip - before the next Big Bang sends it scrabbling momentarily again as up to "over 175 bhp" is fed through it all of a sudden. But then it can recover once more over the next 294-degree power shut-down - and so on. This new approach to GP-winning power delivery allows you to use handfuls of throttle far earlier and harder coming out of a turn without unhooking the back wheel, where before even part throttle incautiously applied would make you think up new grammar in body English to correct the resulting slide. That, and closing the throttle in sheer panic, which of course is not the Doohan way: on the old bike, he lived with the slides but turned them into his trademark "darkies," the long black calling-cards on the tarmac to say 'Mick woz here' via the rear tire. Now, you can use full throttle much sooner in the corner, without the rear wheel losing grip. At the same time, this gives the rear tire a much easier time and, I should imagine, allows you to use a softer compound in race trim than would have been necessary in Darkie Mode. Because the engine's power delivery is so much easier to cope with, the whole bike is less tiring to ride - a crucial factor in a long and arduous 500cc Grand Prix. You don't have to expend precious energy physically willing it back into line, only concentrate instead on making the most of the opportunities the new engine layout offers you. In my case, that meant lapping Suzuka three seconds faster than I'd ever done before on any' bike, entirely thanks to the confidence the NSR500 now inspires, mixed with respect - and only a dash of fear! Part of this sustantial improvement also goes for the chassis, which I originally thought had been quite drastically improved over previous versions, that tended to understeer under power and be hard to lay into turns. Imagine my confusion therefore, when HRC staff insisted there were no major changes between the 1991 and 1992 chassis designs! Yet the newer bike is unquestionably better steering and more

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