Cycle News - Archive Issues - 1990's

Hour (with three Kawasakis in the first five, easily the best showing by any manufacturer) and winning races at the first and last rounds of the World Superbike season at Misano and Phillip Island. They also won another in the middle of the. year at Laguna Seca - which might have been two, before Gobert pushed his luck too far after zapping John Kocinski in a most improbable passing spot, only to fall off later on in the lead. He came even closer to winning another race in the next round at Brands Hatch, still rnore improbably leading the thundering herd of desmo V-twins on a track tailor-made for them, before finally surrendering to Pier-Francesco Chili's Ducati in the final few yards. Then carne the Sentul smash which sidelined Anthony for three rounds while he mended non-surgically, dropping him to a lowly eighth place in the final points table, one pla.ce below teammate Simon Crafar, who had a solid season with several top-four finishes, including a second at Donington. Either way, not a true reflection of the season for the factory or either rider. Didn't think Kawasaki won at Misano, huh? Well, in that case you must be Italian, because everyone else in the superbike world reckons the FIM needs to have its own rules explained to them after confirming the disqualification imposed on the Muzzy team after Gobert's second-race win in the Italian Opel1ing round, on the grounds that fitting restrictor inserts to the Kawasaki's carbs Hopes were high for the new short-stroke 750cc screamer but a' lack of top-end power plagued the team all season. represented an illegal modification: Presumably if they'd fitted them to the cylinder-head intakes, that would have been okay! aut compare and contrast Kawasaki's feat in making its new kid on the block into a race winner right out of the blocks, with Suzuki'sJess-successful season-long efforts at world level with its considerably more highly vaunted new GSXR750. Hrnmmm. However, not all went well after that debut "win," as the chance to ride the Gobert bike by taking part in a two-day pre-race test session at Albacete, while Anthony was off, underlined. While the ZX-7RR's new chassis delivered improved corner speed (see technical sidebar), optimum setup was critical and not easily achieved, though the team did do a lot of testing during the year, and Simon Crafar's experience plus the efforts of Ohlins suspension expert Jon Cornwell helped shorten th.e process. Inside the ZX·7RR K awasakVs success in develo.ping an all-new superbike that in its debut season won World Superbike rounds and defeated the all-conquering DuHamel/Honda combo to win the prestigious American title straight out of the box has been understated, and underestimated - especially since, according to Muzzy Kawasaki's WSC team boss Steve Johnson, the bike is radically different from the ZXR750 which took Scott Russell to the world title in '93. "This really is a 100-percent-new motorcycle, not just an update of the existing model, and one that we and the factory had to develop from ground zero for this season," Johnson affirms. "The only holdover from the '95 ZXR750 was the rear axle - everything else was new on it, including both th~ chassis and engin.e package. "But Kawasaki really did a good job getting the bike to us early, and we did lots of good testing over the winter, which got us up to speed in time for the first race. It wasn't a surprise winning in the first round at Misano; we knew we had a good package for tracks like that where top speed wasn't a factor." How come? "Well, corner speed was up straightaway with the new chassis, and even though we were down on top speed compared to before, we knew that would come eventually. But the new frame was better right out of the gate - not necessarily because it was stiffer of itself, but because it no longer caused the whole bike to flex. "The old ZXR would pump a lot in turns, regardless of whatever changes were made to the suspension or chassis setup, whereas while the new ·bike will still do that if it's not properly set up. The difference is now tltis can be dialed out - as you experienced for yourseU at Albacete." True, but e'(en then, I didn't sample the biggest fix of all, which the team made up d,e week after my test, when Crafar's last six laps in the dying sunset of th.e Albacete test session convinced them this was the way to go. "After the problems you guys were having last week, we made two lockup bolts for the adjustable rear swingarm pivot," said Johnson on race day at Albacete. "This means the swingarm bolt is fixed to one side of the chassis, so as you tighten it, ypu pull the other side over to it and lock everything up. This makes it all a much mOIe rigid package, and gets rid of a lot of the chassis. windup and suspension pumping, which was our main handling problem on the llew chassis this season/' Crafar's fine pair of fourth-place finishes on a Spanish track unsuitea to the peakier in-line fours, followed by Gobert's dou- Though he went out of his way to steepen his learning curve this season, Gobert's self-admitted inexperience in chassis setup was great!y offset this season by Cornwell's expertise, especially as the Canadian technician is an Expertlevel road racer himself, as well as being a fast man on dirt ovals. That allowed him to relate more closely to Gobert's MX-Elerived riding style and set the bike up accordingly, using much more balanced settings than Anthony's '95 combo of a hard rear and 'Soft front. Combined with Dunlop's comeback on the tite front after the disastrous aftermath of the Kobe earthquake, Kawasaki had a much better handling package this year; well, mostly.... ble-up Aussie race vic.tories, confirmed Kawasaki has surely cracked its handling hassles with the new setup. n,at leaves the new short-stroke engin.e as the main target of R&D attention over the close season, and in particular the worrying lack of straight-line speed, clearly apparent all season long, even on a short circuit like Brands Hatch, in Gobert's battle there with Pier-Fran.cesco Chili. Yet by fast Phillip Island, this was already better, though it was only thanks to Anthony's awesome speed in the last, fast turn heioIe the main pits straight that he could overcome this handicap, especially vs. Slight's much faster Honda in the second race. All the el1gjnes the team used this season in WSC were built in Japan by the factory, then maintained and updated by Muzzy. The basis for them however is the ZX-7RR kit parts, which include a lighter crank, a wide choice of gear ratios (even if the six-speed gearbox still isn't extractable, as it is on the new Suzuki, meaning the engine must be split to change a ratio), gear-driven oil pump, 13.7:1 forged pistol'S, valves, springs and camshafts - whether chain or gear driven. Titanium connecting rods and valves have. been tried and are still used occasionally, though without any significant performance improvement to justify the extra cost. The large radiator also is a kit part, though the stock one suffices in anything below 70 degrees ambient. Inlet tracts are now 3mm wider, up to 41mm to increase gas speed and help cylinder charging, and matched to newly homologated 41mm Keihin FCR flat-slides, though the smaller 39mm carbs- used before also were permitted - but not, says the FIM, fitted with inserts to further reduce choke size in pursuit of improved acceleration on tight tracks like Misano, at the expense of topend power. The '96 motor also has extra crankcase webbing for increased stiffness, as well as braced-in cylinder liners in the block, same as on the ZX-9 Ninja. But in developing the new 73 x 44.'7mm short-stroke 'engjne for the ZX-7 (compared to the old ZXR750's 71 x 47.3=), complete with shim-under-bucket valvetrain to replace the rocker-arm system used before to achieve greater reliability at higher rpm, Kawasaki presumably was aiming to obtain more power with increased revs - bu t it hasn't turned out that way. "It revs more, but to be honest it doesn't make power up there, at least not On the dyno," Johnson says. "But on the race .track, especially somewhere like here at Albacete where you squirt it wide open Just in short bursts, the only way to get it to accelerate is t6 tighten up the gearbox, using much closer ratios compared to the old engine - more like a 250 or something, then rev it tight. "Last year's longer-stroke motor actually made more peak power at higher rpm than this year's, so there's still something missing with the new engjne." Kawasaki is at the same point now as·it was at the end of '95 with the old bike in terms of horsepower figures, over 155 bhp at the gearbox. A year ago that was just about competitive, but The "mostly" part caIJ:le first for me at A1bacete, with 10 laps on a well-used 16.5-inch rear Dunlop, which uilderlined how important it is to have fresh rubber to get the kind of grip a lS0-plusbhp bike requires. Dunlop's 16.5 rear delivers. improved traction on the angle, compared to the same company's 17incher, whereas Michelin's 16.5-inch tire· used on the works Castrol Hondas 1'd test later that month in Australia offers improved side grip arid thus enhanced corner speed, at the expense of traction the opposite of the Anglo-Japanese rubber. But the 16.5 Dunlop does go off quicker than the 17-incher, a fact I experienced for myself at Albacete. As the after the huge leap forward by Honda and Ducati this season, it's off the pace. But whereas the old ZXR delivered that power right at the very top end, at 14,500 rpm, the new short-stroke motor peaks at 13,200-13,500 rpm, then holds that power right up to the 14,5OO-rpm rev limiter. "You might think from looking at the numbers that you'd need to short-shift the thing," Johnson says, "but that's not the case. You have to rev it out - Anthony hits the rev limiter in every gear, while peak torque is actually 700 revs lower on this bike than the old one, which is weird, because it's a short stroke. There's some secrets still to unlock, that's for sure." Still, you can't help getting the feeling that the new engine is part of Kawasaki's five-year plan for world domination of Superbike racing - short-stroking the motor puts the basic architecture in place for the kind of 16,000 rpm-plus engine revs and sky-high power outputs"'Formula One cars are now obtaining albeit with the aid of pneumatic valve gear and gear camshaft drive. Kawasaki may not have positive valve operation - yet but the· factory-built works engines used in WSC do indeed aheady have gear camshaft drive, even if the results so far haven't been what the team had hoped for. On the old bike, the Muzzy telemetry confirmed the geardrive engine accelerated better and it also felt crisper as well as providing more horsepower. Presumably, this was due to moreprecise eam timing, which tests show to be accurate 85 percent of the time with gear drive, comp=d to 60 percent with a chain - though a belt is still better than gears, because there's less frictional loss. ' But while. the gear camshaft drive was a definite improvement on the race track with the old ZXR motor, the new one has )'0 gain when you put the gear drive on, and the reason for that eludes the team. Though the bike 1 rode at Albacete announced it had gear-driven cams by the rattle it made soon as it was fired up in pit .Jane, Simon erafar ran a chain-drive motor all the second half of the season, just because that was the one he preferred. The jury's still out on Kawasaki's other experimental gizmo as well: the adjustable carburetor trumpets. The team began experimenting with these last season, and they might be expected to be even more of a benefit with the short-stroke motor, in terms of extending midrange power once the team starts to get serious numbers up high. "We have cried them," Johnson admits, "but they're still a prototype piece. The idea definitelJ' works, but the problem is the contamination from dirt and ensuring smooth 'operation over the length of a race. But it does do what it's supposed to do - just needs more development, which we can't do at a race meeting." Muzzy's hands-on work on the variable throttle venturis has come to an end, anyway, since they're banned under U.s. superbike rules and the team is reputed to be handing over Kawasaki's World Superbike operation to a German-run team for 1997. They'll be missed. 27

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