Cycle News - Archive Issues - 1990's

play of power-understeer that is quite ha rd to overcome. This might be a function of geome try an d setup, so cou ld be d ialed out with less trail with the use of different offsets. Butin fact the Birnota did steer quick ly an d chan ged direction rea lly well in the ch ican es, probabl y because of the lo w cen ter of gravity the SLC chassis design delivers. Right now the Bimot a' s chassis.is a lo t better than the engine. Handling is light, the steering p o s it iv e, and the Oh lins suspension p ackage is nice ly set , up an d quite responsive. You can keep corner spe ed up to un likely extremes for a four-cylinder Su perbike, tha nks to a combination of the low cen ter of gravity, 54 / 46 percent fro n t-end weight bias, a good choic e of Michelin fron t tire an d rea lly good setup on forks , All I w ould have changed would have been a little mor e rebound damping on the front, to stop it bouncing off com pression when yo u hit th e bump a t th e e n d of the strai ght under heavy braking. Speak ing of which, the Brembo stee l discs fitted to the Bimo ta were a real d isappointment, with not nearly as much bite as I have come to expect from their metal brakes; why not cast-iron, like on the Ducat i? Th e net resul t is th a t you have to brake earlier than you'd exp ect for a bike w eighing 356.4-poun ds , the four-cylinder weight limit. Back to the engine aga in , though . Forget short-shifting to keep th e,bi ke stable through the tr io o f le ft-h anders leadi ng on to the Misano back straig ht, as yo u mi ght d o on a Su perbi ke with more midrange torqu e than the Bimota. The 138 rea r-wheel horsepower is delivered at 13,100 rpm, but the engine is safe to just 13,700 revs - w ell, th at's w here the limit er is set, anyway! The actua l p ow erband is quite ha rrow - abo u t 200 revs of stro ng punch, making the lack of fierce engine acceleration a bit of a problem '; an d one th at you have to wo rk th e gearbox hard to overcome by keepin g the revs up high. The rather m echani ca l-feeli n g sp ee dshifter obvio us ly help s you do this, but I can't say it feels as if it' s doing the gear box a lot of good, and per haps this is one exp lan ation for the fac t that they keep br eaking fourth gea r in the closerat io Suzu ki RR gearbox. Bott om gea r on this is too low to be ever u sed once you're o ff the line, but second is too high, which furt he r affects th e p ickup ou t of slow turns like th e tight left in the new section of the Misana track. It just doesn' t get up and go till the digital tachometer is in five-figure forma t. The tach , by the way, is even more illegible than the one fitted to the works Tesi I raced for Bimota a cou p le of seasons ago. You can 't make out how many revs the engine's d oing w hen the sun is shining - so no choice but to ride it on the rev-limiter. Tough! N ice bike, shame abou t the motor that was m y bottom line to M a rconi af ter th e end of m y 20-lap spin. H ow come? Does Bimot a have work to do on the m appin g for the EFT / engine m anagement that wo u ld cu re that disjoint ed p ow e r delivery and u nru ly t hrottl e response? "It' s a combi nation of electronic and mech anical developmen t tha t we sti ll need to do," says Ma rconi. "Remem ber that we o nly s tarte d th is p roj ec t just before th e season began, so we're n ot yet very far along the road to perfection. Most other manu facturers w ou ld have spent a year developing the bike before they eve r came to a race with it - but we es ta blis he d a th ree-yea r program for Superbike racin g when we d ecided to return to it officially. This year we want- (Left) Powered by Suzuki's "old" GSXR750 motor, midrange power leaves something to be desired. Large, 46mm throttle bodies have variable-length intakes to help keep Intake velocities high at lower eng ine sp eeds, but the fuel injection need s more development to be effective. (Left) Brembo brakes are steel, and less effect ive than expected. (Above) The digital tachometer is virtually illegible in bright sunlight. Redllne is 13,700 rpm. ed to ge t the handling 100 percent right, w ork on d eveloping th e engine to the p oint w e cou ld make a d ecision wha t to do with it, and establish our partnership with Team Greco, who are Bimota's official factory race team. For '96 we consi dered adop ting the new Suzuki GSXR750 engine, wh ich is obviously designed to be raced , but there are tw o prob lems. . One, we have to d eve lop a new ,SB8 mod el fitted with this engine, and then build sufficient quantity to ho mo loga te it . Even th ou gh th at number ha s just been reduced to 100 bikes, it's still a big commitment we'd h ave to make in a short tim e; Two, we'd have to throw away the resu lts of our season of work on the older engine, which we now kno w we ll. So I thi nk we prefer to compl etely re-engineer the in ternals of the older Suzu ki engine to make it rev nigh e noug h t o gi ve good p ow e r an d improve reliability , like Yoshi mu ra did in th e USA w ith th eir bikes. Th en for 1997 - ye s, p erh aps an SB8, once th e Suzuki factory team has ironed out the inevi ta b le prob lems you m u st surel y come across with an all-new mo to r in its first season." In raci ng the engine dur in g 1995 , Bimo t a identified four ma in weak p oints: the clu tch (which exp lo d ed on the bike Russell Wood was riding alongside me at Misano!); the big-end connecting rod bearings, which last ju st a sing le meeting; the gearbox - wi th fourth gear the main culprit; and the low rev ceiling - exceed 13,700 rp m, an d you' re gu ar an- teed to brea k valves an d spri ngs, says M a r con i. "We lost a lo t of tim e be cau se w e designed the camshaft and exhaust syste m, an d mapp e d the engi ne- management system, on the basis that the engine w ould rev safely to 14, 000, " h e says. "Whe n it wouldn't with out breaking, due to valve float, we had to red esign everythi ng, and that set us back." Bimo ta h as flowed and ported th e Su zuk i eng ine's cy linder h ead, res h aped th e combust ion chamber, fitted thei r own cams haft and u ltraslip per tw o-rin g pistons (mounted on titanium rods with a lighten ed crank an d light er alternator), and Marconi also wants to lighten the clutc h considerably. "I 'm sure that's th e main reason it won' t acce lerate," Ma rconi says, "an d the Japanese kit dry clutch is almost as heavy. I'm not worried about whee lsp in if we li ghten e ve ry th in g, so th a t' s a main p riority. But for '96 we'll also have o u r own closed- up gearbox with a choice of ra tios, titanium valves and specia l springs to sto p th e va lve floa t and let the engine rev, improv ed cooling wi th a new radiator - it runs much too hot at presen t, instead of 70 degrees max - and a better airbox with different du ctin g. I h on estl y believe we can becom e regular top -10 finishers with this engi ne in co m plete ly re-engineered form in 1996, especially if we can impro ve th e curved in let tra ct, which is the greatest h a n di cap to co m petitive p ow er . But we 're working on it. Though our biggest objective next season is to win the European Supersport 600 title with our new fuel-injected YB9, the Superbike project is very im po rtan t, because it's p art o f our overa ll plans for Bimota' s fu ture. We're a company de pende nt on su ccess in racin g for our image, our prod ucts, our whole existence. We can't afford to just make up the numbers." f~ BiMOTA SB7R Specification Engine Liquid-cooled, DOHC, four-cylinder, in-line four-stroke withfour valves per cylinder and central chain camshaftdrive Bore x stroke , , 70 x 48.7 mm Displacement _ , 748 cc Output _.... ..... ..... .... . . .•... . . .. . .. . 138 bhp at 13,100 rpm Cat wheelJ Compression ratio _ 11.8:1 Fuel/ignition system . TDD/Bimota electronic fuel-lnjectlon and engine-management system. with one injecter per cylinder and four 46mmthrottle bodies Gearbox ' s -speed Clutch , Multiplate oil-bath Chassis _ Aluminumtwio-spar Suspension Front , 46mm Ohlins inverted telescopic forks Rear Fabricated aluminum swingarmwith rising·rate linkage and single Ohlins shock Head angle , 23.5 degrees Trail. , , ,, 96mm Wheelbase ' , , _ 1380mm Weight , , ,. , 356.4 lbs, with oil/water, no fuel '" 54/46 % Weight distribution, front/rear .. , Brakes Front Dual 320mm Brembo cast-iron discs with four-pisto n Brembo calipers Rear , .. Single 21Omm Brembo cast-iron disc with two-piston Brembo caliper Wheels/tires Front 12/6 1·17 Michelin radial on 3.5Q.in. Marchesini wheel Rear , 18/ 67·17 Michelin radial on 6,OO·in. Marchesini wheel Top speed ' ' .' _. . . . . . . . . . _ 181 mph C SalzburgringJ Year of construction , , , . 1995 Owner . . . . . . . . . . . , Bimota SpA. Rlm inl, Ita ly 3

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