Cycle News - Archive Issues - 2000's

(Left) The author gets down to business on Andrew Pitt's factory Kawasaki ZX-6R - the bike that is cun-ently third in the World Supersport Championship. (Below) The naked version. The ZX-6R is right on the World Supersport weight limit of 367 pounds - without using carbon bodywork. dimensions, until the arrival of the current CBR600, had the shortest stroke in the Supersport paddock. But whereas Honda has only just started to take advantage of the extra revs such an engine permits in pursuit of top-end power, with 16,000 rpm engine speeds now a fact of life amongst its leading contenders after two seasons with revlimiters set 1500 rpm lower, Kawasaki has moved in the opposite direction. So says Team Eckl's Supersport tuning guru Martin Gopp - a man with a large letter 'K' carved on his heart and green Kawasaki blood running in his veins, who insists that, as before, it would be possible for any privateer team to build a complete replica of the Pitt/Macpherson mini-Meanie for no more than $13,000, using only parts readily available for customer sale. "On this bike we've used even more standard parts than on the old one," says Gopp proudly. "We've concentrated on improving materials via the factory kit parts, and aimed to improve the engine's spread of power, as much as top-end numbers. I'd rather not comment on the rumors about our engine's dyno figures from Akropovic (well - okay, but his smile as he says this speaks volumes), but if for instance this were to be true, it would only have come about as a side benefit to our main aim of making the bike even more rideable, and reliable. We only had one technical DNF last season, so that's a good basis for 2001." To achieve this, Gopp has raised the compression ratio to 13: 1, a full polnt higher than the older bike, fitted kit connecting rod bolts, big-end bearings, and a smaller oil pump to improve acceleration via reduced friction, plus the latest kit camshafts, still with stock lift as required by Supersport rules, but with longer dwell. In fact, these are the same as catalogued by Kawasaki from 1995-98, just as he used in the older bike rather than the '99 versions that affected reliability, because the cams opened the valves too fast. But kit cam sprockets now allow the valve timing to be varied a little, there are stiffer kit springs on the stock valves - now at last with dual springs on the inlet valves on the new model, though still a single one on the exhausts - and a kit igniter box to raise the rev limit, though this is in theory at least not as high as the street ZX-6R runs. "Kawasaki say the new ZX-6R is redlined at 14,500 rpm," says Gopp, "but our race engine is revlimited to 14,200 rpm, and makes peak power of 114 horsepower at the rear wheel at just 13,000 rpm, on a static dyno with only a little wind flow. I'm not convinced the single air intake 'mouth' on the new bodywork delivers such effective flow to the airbox as the old system with twin side intakes, and I believe the big central duct contributes to instability at high speed, especially in a crosswind, when the air gets under the lip of the duct and lifts the bike up. But for sure there's even more power at speed thanks to the ram-air effect." But even in real-world track use, this extra top-end power - Macpherson's '99 bike delivered 108 hp on the same dyno - hasn't been achieved at the cost of making the ZX-6R more peaky than before. Far from it: though it still likes to rev and feels strong and unburstable, the engine seems quite a bit more muscular than on· the old model, with a wider spread of more usable power, which paradoxically means you don't have to rev it right out to the revlimiter in every gear though neither rider's bike had the change-up light connected when I rode them, and lain Macpherson admits that he doesn't even look at the tach any more, just shifting gears around 13,500 rpm by the sound and feel of the engine. Doesn't stop him from buzzing it on the downshifts, though, which the street-pattern gearbox he favors does invite you to do as you stamp on the lever - the permanent on-board telemetry the bike carries (while still easily meeting the class 367 -pound weight limit, without using any carbon-fiber bodywork or titanium fasteners) reveals lain's record overrev as being 15,200 rpm, at Monza! The kit gearbox fitted now has a completely different set of ratios compared to the street ZX-6R, with a longer first, shorter top gear, and all the others in between closed up - plus Gopp has done a lot of work on the stock selector drum to smooth out the shift mechanism and speed up c1utchless changes, though of course there's no powershifter since Supersport rules don't allow one, and the Eckl team doesn't bother with the Alstare Corona-inspired way around this, with an ignition cutout button the riders can thumb as they hit a higher gear. That same telemetry tells them that Macpherson loses drive for just 2/1 OOths of a second when he changes up - so maybe there's no real need. Instead, the Kawasaki has a great, clean change action with a short lever travel, making sure I didn't miss a single shift in more than 50 laps spread over two days, and with the kit gearbox's ratios ideally chosen to suit the great-sounding engine's nature, allowing you to keep it revving in the fat part of the powerband between 10,000 and 13,000 revs. But it pulls cleanly out of the Most hairpin as low as 6000 rpm, where the K-TRIC system fitted to the 36mm Mikuni carbs helps deliver a crisp pickup and the beginning of a smooth, progressive power curve that sees engine speed build even more zestfully than before, thanks to the reduced inertia from the lightened engine internals. This sees almost seven pounds saved from the weight of the engine by adopting not only magnesium cylinder-head and clutch covers, but also a closed-deck cylinder block with electroplated bores, which does away with the previous iron liners, and results in a stiffer, as well as lighter, block. Even more importantly, just over two pounds has been shaved off the crank weight, which together with a sevenpercent lighter flywheel mass (including the rotor), results in much less bottom-end inertia, which helps explain the brisker throttle response and quicker pickup from low revs of the new bike. And to help produce that enhanced power output, the new ZX-6R motor now has a hemispherical combustion chamber developed directly from the factory ZX-7RR Superbike engine, with a 7mm shorter inlet port (alone responsible for 1 hp in extra power, as well as 500 rpm extra on top), and a straighter ram air hit of cool air to the airbox, which Kawasaki says improves cylinder filling at high speed, even if Gopp isn't convinced it's necessarily better. The Eckl bikes run differentially sized intake trumpets for the Mikuni carbs, with those on the middle two carbs 5mm shorter than the outer two, to improve midrange pickup between 8000-10,000 rpm, says Gopp, who also declares the carburetion on the bike is still just as sensitive to atmospheric changes and tricky to set up as before. I had a good illustration of that on my late aftemoon ride on Pitt's bike at the end of the first of the two days of

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