Cycle News - Archive Issues - 1990's

through th e lef t fra me s par as on the works F-l racers, leadi ng the team to pressu ri ze the air box differen tly than before, but just as effectively. The gea rbox problems of last season ha ve been resolved on the kit bikes as well as the Muzzy machines by transferring muc h of the tech nology from the Fl/Endurance racers, with bigger shafts and redesigned gears and selectors, and n ow there are no problems. However, the wide choice of ratios from before has been red uced , so now there are "only" three d ifferent ratios per gea r in the sixspeed gea rbox, except for third where there's only one. choice. But the chan ge action is mu ch improved, say the riders. St ill n o s ig n o f a dry clu tch o n th e Kawasakis, though - and no need, says Mu zzy. "First of all, it depends on the d egr ee of w etness as to how much advantage you mig ht ga in from having one," he say s. "Bu t I also remember when I worked for Ho nda 10 yea rs ago, I was always asking them for a dry clu tch, till eventu all y they gave me one, even though they said it would make no differen ce. Darned if I d id n' t pu t it on the dyno an d fi nd th ey were completely rig ht - no power d iffere nce a t all: was m y face red! Same thing about large carbs: people say we must get a lot more power from the 41mm Keihin CRs we ca n run in America, compared to the 39 mm ones we run here, b ut there's h o n e s tl y no difference in absolu te p ow er - only we use the big ca rbs a t some tracks in the USA to get a softer midrange and less wheelspin compared to the smaller ones. Once you get the minim u m op timum carb size fo r the engine, and especially the righ t type of carburetor, the rest doesn't matte r a whole lot." The s tiffe r, h e a v ie r chass is a n d swingarm - only braced on Slight's bike, b e it no ted - mea n th a t Kawasaki no longe r need to fit a n on- funct ion ing starter motor and generator to beat the we igh t limit, with the bikes scaling 367 pound s without the benefi t of any titanium or magnesium, or any carbo n (fibe r) a p a r t fro m the bra k es a n d shrou ds . Getti ng down to the new 352- pou nd limit next season shouldn't be at all difficult, though - but Kawasaki hope the rel iability and s peed of thei r bikes (Slight was the only works rider to score in every one of the first six races) will be good enough to make them World Champions this season, without having to wait for another little ed ge from the rulemakers. This could indeed be their year. Yamaha: New kid on the block The arrival of the new YZF750 has boosted Yamaha's chances of success in World Superbike racin g, but as with any new model, it's taking a while for the teams to complete their learning curve in setting the bike up ideally, not helped by the fact that both the BYRD and Pepsi -Galp teams, who are Yamaha's main contenders for honors, got their bikes only a couple of weeks before the firs t round at Brands Hatch, and have been playin g catch-up ever since. Still, Fabrizio Piro vano especially, as well as a Rymer riding injured for most of the first part of the season, have impressed with their ea rly showings on the YZF, w hich is evid en tly a step up fro m th e old OWOl - thanks to a number of changes learned from racing the older model. Main improvements o n the 72 x 46mm 20-valve engine are the arrival of flat-slide carbs - the sa me 39mm Keihins that Kawasaki uses, and a break with tradition for a company previousl y wedded to Mikuni - and an all-new cylinder head, with different inle t port- .... 00 ~ Q) ..0 S Q) ~ 0.. Q) CJ) Th e Yamaha YZF750 is competitive, but as is the case with any new model - the race teams a re struggling to find the ideal setups. ing to take advantage of the new carbs, plus a different design of combustion cha mber, with a slightly wider valve angle. BYRD's eng ine wizard Beppe Russo has do ne some extra work on the head himself, but says that the combination of kit and factory parts he has to work with are excellent - he has no need to sou rce any parts in Italy . " Basically, Yamaha have done everything I cou ld have asked for in revamping the engine," says Bepp e. "A nd it's already very pow erful, even at this early s tage in d evel o pm en t. The on ly rea l problem we 've encountered is learning how to set the carb uretion up properly, whi ch is just a matter of testing and getting used to the d ifferent settings compa red to the CV carbs we used before. On the chassis side, we've had a lot of p roblems wit h the rear suspe nsion, but now Yam aha has delivered a new rea r link, I th ink we've cured that. But the bike is very fast Fabrizio says he hasn't yet been passed by another bike in a straight line ." That claim is born out by trap times (see Honda chapter), making the BYRD Yamaha a real contender right off the blocks. Ru sso says the engines in th e BYRD bikes are fitted with the limitedav ailability 'A ' kit parts, comprising of s p eci a l camshafts, a lighter cr a n k, a cl ose-ra ti o gearbox (with a choice of alternative ratios to com e later), a dry clutch. sourced from the fa ctory ' s Suzuka 8-hour program - comp lete with blanked-off oil filler - a carbon fiber airbox, speci al va lve s the same s ize as stock, a works e xh a us t w ith out a ny EXUP fitted , two ev en th icker water radiators than last year, and a special ignition with rev limiter set at 14,100 rpm - but still non-programmable, in sp ite of Russo's pleas to the factory for a digital unit with a t lea st a ch oice of curves, or one he can reprogr am . The result is an eng ine that delivers exactly 150 bhp at the gearbox on the BYRD dyno, at 13,800 rpm, yet wh ich Pirovano says gives good midrange and is easier to ride than last year's aWOl but on ly once the carbura tion is dialled in, something that takes longer with the flatslides than with the old CVs. "We hav e the same top speed as the Muzzy Kawasaki s," he says. "Bu t they can pull two or three len gths on us in midrange. Mertens tried to pull out and pass me on his Ducati down the long straight at Hockenheirn, but couldn't - he had to get bac k in m y draft. The Ducatis only have the edge on braking and acceleration out of turns , because of their lig ht weight. Now we 've ca ught the m up on engine performance." The Yamaha has a nas ty hab it the teams are working to c ure, th o u g h , which is tha t when it hits the rev lim iter, the ignition cuts out completely, ra ther than switching to intermi ttent firing of th e cylinders as is more us ual now a days. If th e rider is h ar d on th e gas w hy else would he hit the red line - this allows mi xture to bu ild up in the inl et tract wh ich s ud denly de nona tes when the ignition cuts in agai n. The loud ban g th is ca uses coul d b e h eard ec hoi ng ro und the stadi um at Hoc kenheim, and the exp losion is strong enough to have bl own the ex h a us t h ead ers off th e e ng ine o n Merk e l' s b ik e a t Brand s ! Luck less Fred had the sa me thing ha ppen to him again at Hockenheirn, which is wha t caused him to crash in the first hea t, when the engine exploded into life coming o ut of the first turn and unhooked the back wheel. A new rev ' limiter program is a necessity, says Russo . Bet the riders agree. The YZF chassis is completely new compared to the older aWOl , with the engine rotated backw ard s five degrees in the chassis to enable the wheelbase to be shortened , just as Ducati are doing with the V-twin desmo on the for thcoming 916. The result is a shorter, smaller bike tha t has more weight on the back wheel compared to the OW , a feature that is further promoted on the BYRD machines by the factory swingarm that is 30mm shorter than standa rd. Ohl ins sus pens ion is fitted to the BYRD bikes (the forks the new 46mm golden goodies), bu t a lot of work has been need ed on th e rear suspension to get the bike handling remotely well. All YZF owners have been compla ining of the same thing - a standard rear link that gives progressive susp ens ion response over the first ha lf of its curve, then freezes u p: if yo u're unfortunate enoug h to h it a b ump a t this po int, it goes righ t through to the bu mp stop and bottoms ou t, with imaginable result. "Considering th at Kawa saki h ad exactly the same problem two years ago with th e ZXR , you'd th in k Yamaha wouldn't have made the same mistake," says one YZF rider who better remain anonymous if he wants any more help from the factory. "It makes you wo nder what on earth the Japanese test riders do with the bikes before they sign them as fit for p roduction - a novice could have told you the bike didn't h an d le with the stock link." Ha rsh words, maybe - but a fair point: lightning can strike twice - well, in adjacent fields! Bu t that apart, the new YZF is right on the p ace almost straight out of the box, a t this very ea rly stage in its develop me n t cycle. The b ike is very light, scali ng right on the 363-pound weigh t limit eve n w ith a 6.6-po und alt ernat or and 4.4-p ound starter motor filled as ballast- Yam ah a will find it easy to meet the new 352-pound weight limit n ext seaso n, even fi lled with Pi rova nos trad emark sea t pad , whic h help s pu sh his sligh t weight fur ther forward to load up the front end, yet we ighs a cool four pounds. The BYRD team run Brernb o's new 290m m carbon di scs, shroude d for fast t ra ck s like in Germany, w hi le th e Italian-entered bikes are now fitted with a new and very capable telemetry package developed in conjunction with a n Italia n com p uter company, which has 16 potential channels of data record ing, of which at present they're using only eight. "Th e diagnostic sys tem has really helped us in developing the new bike in . th e short time available," says Bep pe Russo. " And the fact we've become as competitive as we have with it so fast is partly thanks to having it. But there are many other areas we plan to monitor in the future, to take full advantage of its capacity." Yamaha has taken an important step forward with the d ebut of th e YZF, tho ugh rumors continue to circu late that there's a fuel-injected version waiting in the w ings for next season, to meet the challenge from Honda, that will supersede the present carbureto r bike..Maybe, but befo re that turns a wheel in public, Yama h a may have made it to vic to ry lane with the present YZF. off Honda: Still waiting and hoping With the RC45' s arrival p ostp oned until next se as on, Honda 's sole rep rese n ta tiv e in World Superbike, Oscar Rumi's team, must have had a big temptation to sit the season ou t, and use the convenient fact that the Hond a CBR600 single- marq ue class known as the Supersport Championship was be ing 29

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