Cycle News - Archive Issues - 1990's

next-to-last rQund. Still, the Yamaha rider had a secure hold on second in the standings in front of Ducati-mounted Mauro Luchiari and a host of other 748 riders. Clearly, the Yamaha showed its mettle in both straight-line speed and handling prowess. Meregalli's upset victory on home ground at Monza underlined the Yamaha's speed on a fast circuit against twincylinder bikes carrying a 25-percent capacity advantage, while his close second places on handling tracks like Misano, Brno and Donington proved the four-cylinder YZF has the measure of the more nimble twins in the handling stakes, too - especially with the International Supersport class' new 378-pound weight limit applying to twins and fours alike this season. And in the parallel Thunderbike series run as a GP support class (but rumored to disappear next year when the mOre prestigious Supersport World Cup achieves world title status) from which the twins are excluded, Yamahas won four out of the first five rounds, with Dutchman Jeffrey de Vries a close second in the points table at that point with two victories, just five points behind Honda-mounted Yves Briguet, who didn't win a race during the same period. De Vries ultimately finished third in the championship after the final round at Catalunya, where he finished fourth. ot bad for the first year of racing development. Anyone who had the chance to race a Yamaha YZF600R in 1996 and didn't must be kicking themselves. The chance to ride Meregalli's bike at Monza - scene of his narrow but decisive win over the herd of 750cc desmo twins underlined what a competitive piece the new Yamaha is. It's easy to ride, with outstanding midrange engine pickup as well as top-end response, and a good chassis and suspension that makes the Thundercat the most competitive fourcylinder bike in the class right now. Maio's victory as a wild-card rider at Mugello in the Thunderbike round supporting the Italian GP really emphasized the YZF600R's excellence. "We treated it as a competitive prac-. tice session, and ran the bike in supersport form rather than convert it to the more liberal Thunderbike spec," says Belgarda team manager Giulio Bardi. "But we still won anyhow!" In doing so, Maio smashed defending T-Bike champion Yves Briguet's 1995 lap record by no fewer than 2.65 seconds, trapped at an amazing 165 mph past the pits as the Yamaha cruised home to untroubled victory. "1 tried to stay with Meregalli, but his bike was faster and handled better than mine," said Honda-mounted Briguet after the race. Impressive - but even more so when Bardi insists that there's nothing on the Belgarda team bike that a privateer can't buy and fit to his own YZF. "We use only the customer Yamaha race kit, an Ohlins shock and a Termignoni exhaust," Bardi says. "Plus lots of hours of dyno time and experimentation to find the ideal setup. We've got a lot of talented people working here, and that's what makes the difference - it's a real team effort, without any trick paits." The Yamaha engine kit includes a set of cams with longer duration (lift must remain the same under supersport rules); a revised wiring harness and new ignition box which, however, retains the stock 13,800-rpm limiter; stiffer valve springs, though valves must remain the same diameter and be made from the same material, but can be reshaped as (Left) On tight and long tracks alike, the VZF has proven Its ability to run with the 748SP Ducatis, so successful In European supersport racing. (Below) Careful tuning has yielded 118 horsepower from the FZR-derlved supersport powerplant. part of the extensive head work that Belgarda tuner Beppe Russo has invested in; heavy-duty clutch springs; a carburetion kit containing jets and needles; a close-ratio gearbox with higher first and second gears, and a much-smaller ignition rotor as part of the totalloss system which requires retention of the full-size battery to ensure that you can start the bike on the button in post-race tech (failing which, as Ducati rider Camillo Mariottini discovered after forgetting to switch off the ignition in his excitement at finishing third behind Maio at Misano, you get disqualified!). And, er, that's it. All you need to add on top of this are those hundreds of hours of patient work flowing the head, refining the engine, lightening and polishing parts like the crank and rods that you are allowed to work on, and gaining precious fractions of a horsepower with ongoing seasonlong development. Beppe Russo says the changes Yamaha wrought to the YZF compared to the previous FZR, including forged pistons that are lighter and stronger than the previous cast ones, and a new, lightweight cylinder block with ceramic-coated bores, have made it tougher and more reliable for race tuning, as well as five percent more powerful all through the rev range. Peak power on the Belgarda bike is now 118 bhp at 13,700 revs, compared to the 111 bhp he got from the FZR600, but with substantially improved acceleration, even with the bigger 36mm (up 2mm) Keihin CVKD carbs now fi tted. This is thanks mainly to the sophisticated new pressurized airbox system, with twin, side-mounted resonator boxes into which the airflow from the central entry duct splits to improve midrange torque by optimizing airbox resonance, as well as completely separating the airflow from engine and radiator heat. J;lelgarda uses the kit water radiator, based on the FZRl000 EXUP one (which kept the temperature down to a cool 170 degrees for my ride, even using lots of revs on a warm Italian summer's day) as well as retaining the stock liquid-cooled oil radiator. Another key factor is the throttle position sensor (TPS) fitted to the Keihins (which also have their float bowls vented to the same pressure as the ram air, to prevent leaning out at high speeds), which dials up more advance from the ignition, depending on the throttle opening and engine speed, in turn delivering a more responsive, crisper pickup at part-throttle openings. Two laps of Monza are enough to convince you how the T-Cat's astonishing throttle response and take-no-prisoners torque has transformed the bike into such a potent Dueati beater, negating the V-twin desmo's extra punch out of turns that's been its main edge over the fours until now. The Yamaha's midrange pickup is absolutely awesome for a 600cc supersport machine. Pulling a third-gear wheelie hard on the gas cranked over exiting the first chicane at Monza is the sort of thing you expect from a works superbike, but to have its kid brother pull the same trick on you wasn't in the script. It carburets cleanly from 8,000 rpm up in a tight corner, like fup-f1opping from side to side in that first chicane, but it's best to use that close-ratio gearbox with 700-1,000 rpm average drop per shift to keep the motor operating in the five-figure zone. Though Beppe Russo says the crank isn't lightened, it feels as if it is by the way the T-Cat revs so eagerly - from 9,500 to 12,000 rpm there's a really vivid pickup in engine speed, en route to your appointment with the 13,BOO-rpm rev- limiter, which when you do hit it just. flutters the engine, rather than killing it stone dead so you lose momentum. The T-Cat keeps pulling hard all the way to the redline, too, with the precise, light-action throttle delivering sharp, responsive carburetion which Giulio Bardi insists they rarely have to change from one circuit to another. "Once you dial in the CVKD carbs, they're very forgiving, so changes in humidity or altitude aren't so critical," he says. "But the trick to get such good midrange response is to set the carburetion up quite rich, without sacrificing top speed. When Maio slipstreamed past Pirovano to win here at Monza, we knew we'd got the balance right, so we leave well enough alone!" A supersport racer that makes the numbers without being as peaky and high-revving as the ZX6 Kawasaki it has completely eclipsed on European race tracks this year doesn't ask you to work the gearbox so hard, but the shift action on the Yamaha is sharp and precise, even when 1 ignored Giulio Bard's advice and started up-shifting without the clutch, as you'd expect to do with any racer. Giulio regrets that speed-shifters are banned from supersport racing, because he reckons they'd be an inexpensive safety measure, citing the speed of the primary gear fitted to the YZF as otherwise discouraging clutchless shifting. But in 28 laps of the Monza GP circuit, 1 didn't miss a gear once. And the motor's so torquey you can actually short-shift to settle the bike better and work the meaty part of the power curve, like in the middle of the

• Cover