Cycle News - Archive Issues - 2000's

Akira Yanagawa's Kawasaki ZX-7RR sends the rev-limiter cutting in 300 rpm higher. Now for the first time since it was introduced back in 1996, the Kawasaki's short-stroke engine has a genuine appetite for revs with an extra 500 rpm on top compared to previous years, and a sense that revving it that hard is genuinely worthwhile - quite apart from the extra over-rev this offers, this allows you to hold a gear and save two shifts - like between the two left handers coming down the hill at Zeltweg. The extra revs not only give a little more power, they make the power band wider, and this is a big help in improving performance in the gears. "Kawasaki engineers delivered a big improvement this year in the power delivery," says team manager Harald Eckl. "We had quite a good bike in '97, but '98's was too peaky, plus we had a rear shock problem that only made it worse. But the main By ALAN CATHCART PHOTOS BY MARK WERNHAM !'1st, but not least. One of the 1999 Wortd Superbike Championship's most popular wins was Akira Yanagawa's victory at Sugo in the final race of the year - indeed, of the century. After four solid rides at Assen and Hockenheim, while still experiencing the effects of the concussion he suffered in the pre-race warm-up in Austria, the win on home ground was just reward for Yanagawa's efforts - and for a muchimproved Kawasaki. It was an improvement indeed with Yanagawa visiting the rostrum a total of nine times in 1999, compared to just once the year before. So, after a '98 season they'll want to forget, Kawasaki has found the way back with the only bike in the World Superbike paddock that is still fitted with carburetors rather than fuel-injection. Riding Yanagawa's ZX-7RR at Austria's A-I Ring only underlined how far the bike had progressed back down the path of four-cylinder righteousness since the last time I'd tested the works Kawasaki a year earlier at Assen. There, I'd had a vivid demonstration of why the team was struggling to build on the successes of the previous season, when I found myself perched astride a bike that was frankly intimidating to ride - eager to spin the back wheel out of turns, thanks to a very aggressive power delivery, with pretty unstable handling when you tried to put the power down hard and hook up the rear end. It was a real handful, which I can't say I enjoyed riding very much: I doubt if Yanagawa did either. "Our '98 machine was very hard to control," Yanagawa admitted. "Bottom power was too fierce, and this led to wheelspin and bad traction exiting turns, which suspension prob- 26 JANUARY 26, 2000' cue lems we suffered only made worse. Kawasaki engineers must work very hard to adjust this character during the winter months - but as I hope you will see for yourself in a moment, their work is very successful, and this year's machine is a big improvement." I'll say. Dialing up some power on a dry Zeltweg track once the raln had passed wasn't an entry ticket to the two-wheeled funny farm, like it had been the year before at Assen. Instead of the '98 bike's vicious burst of barely controllable power - worthy of a badly mapped fuel-injected fourstroke! - as soon as you opened the throttle on the bank of 41mm Keihin f1atslides in mid-turn, the '99 Kawasaki had a smoother, more controllable power delivery. It was still very punchy, with a meaty th rottle response that was vivid without being snatchy. On last year's bike, getting hard on the gas while cranked over was an invitation to disaster: the suddenaction throttle response not only spun the back wheel, it also sent the Kawasaki into a shake. You had to wait until you. could pUll it upright then get ready to cope with the wheelspin. Doing that cost precious time, in comparison to the smootherdriVing Honda and Ducati. Now, twisting the wrist is the key to unlocking an even more potent powerplant one that produces 3 hp more at the top-end than the '98 bike, yet with a smoothed-out pickup that allows you to put that to good use via the rear ] 6.5-inch Dunlop's fat contact patch. While the Kawasaki is still happy to pull third-gear power-wheelies out of either of the Austrian track's slow first two turns, it'll now do so without trying to unhook the rear tire via an I e n e _ s explosion of power and a steep dose of torque as it does so, nor does it send you shaking and wobbling. It also goes down the straight like never before. After the wheelspin stops and the Dunlop finally grips properly, the ultra-short-stroke 73 x 44.7 mm engine - still by some distance the most oversquare in the World Superbike paddock - drives hard and strong from low down (another improvement) with a potent, linear pull from ]0,000 rpm upwards. There's also a smooth transition to the serious powerband and the bike drives out of the A-I Ring's first-gear second corner from as low as 8000 revs without a hiccup. There's not the same jerky pickup from a closed throttle as in '98, but at 12.000 rpm there's a rush of extra revs as the Kawasaki picks up engine speed even faster, delivering awesome acceleration 'that's surely now the equal of anything else on the grid. Now, though, you can make proper use of this performance, especially by using the race-pattern gearshift to keep the Kaweseki engine revving hard up high, via the well-chosen ratios that keep the engine singing above 12,000 rpm in every gear. The power-shifter built into the programmable ignition is perfectly set up. It's just firm enough to require a prod on the lever with your left toe, rather than changing gear practically by itself whenever you wave a foot at it, as some over-sensitive wide-open gearshifts (like the one on Fogarty's Ducati) do. So when the Kawasaki's trademark junior searchlight mounted on the dash flashes its beam in your eyes as the tach needle hits the ] 4,500 rpm mark, you've just got time to hit the next gear at ] 5,000 rpm before the eager-revving engine factor were the engine characteristics; these may have looked good running on the dyno in Japan, but we have to do a track job, and it didn't work in terms of lap times. Besides that, I've been pushing Japan for some time for more revs, and so more top-end power, which I've always believed was the whole purpose of shortening the stroke back in ] 996 - except to begin with, the bike was slower. Now Kawasaki managed to provide both - a more linear delivery like in '97, but more power, thanks to higher revs. They did a really good job." To achieve the more linear, more controllable power delivery, R&D on the Kawasaki engine's internals needed some serious redirection, as Yanagawa's race engineer Larry Kano explains. "Basically, we were using the wrong combination of camshaft, cylinder head porting, ignition curve and carb settings," he says, "plus the fact all this ran such a high] 5:1 compression ratio, only made it worse. When the short-stroke bike came out in '96, it was slow - so we gave it a heady dose of compression to get it driving out of turns, and it helped get the bike going faster, sooner. So even though in theory it impacts on top speed, we kept upping the compression to try to stay on terms with the competition under acceleration - but then when the other factors in the motor went astray, this suddenly became a big negative. We needed some major juggling with engine specification to fix it - but the guys in Japan did that, and it's worked." For '99, this included a new design of two-ring piston, rebalanced crankshaft, completely altered porting to

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