Cycle News - Archive Issues - 1990's

eTECHNICAL e 22 W C am shipSup_rbike_ _ es orld h pion e _ _ Seri_ bias the rid ers had to live with befo re, wh ich gave the Du ca ti its less th an ideal handl in g in certai n circu m sta nces. In addi tio n to working on red uci ng weigh t, Bordi has also developed new bodywork in the Pininfarina wi nd tu n nel, since homo loga ted o n th e 85 1SP sport production ro adst er s: a nother 'u nfa ir' advantage Du cat i has as a small -volu me producer is th at suc h a fundamental change can be more quickl y introduced and legitimized for SBK raci ng, since th ey need o nly build 200 mach in es to th e new format in o rder to homol oga te it , agains t the 1000 of a j a panese mak er. The '9 1 desm o therefore has a 5% improve m ent in wind pen etration, as measured in Cx , th anks to a new fro nt m ud guard sha pe , a rear mud guard th at ru ns under th e swi ngarm to reduce turbulence, a stra ig h ter, high er run to the ex ha usts which tu cks th e silence rs closer to th e sea t unit, and a closedin front fai ring sectio n which on ly a llows ai r to flow through th e radiat or, not arou nd it. T he in creased aerodynamic efficie nc y th ese changes offer not o nly improve th e Du cati 's stra igh tline spee d, but a lso ma ke it more stable at speed. Ap art fro m new-t ype Ohli ns forks - bu t no sig n yet in Superbike raci ng o f the Swedis h co mpany's semi-active rea r suspens ion system presen tly bein g developed with T eam Rob er ts in 500 CPs - th e rest of th e Ital ian bik es' chassis spec is unchanged from last yea r, thou gh o n e inter esti n g but crucial factor has tend ed to go u nob served as th e season go t u nderway. Du cati is the o nly factory to have a t least one of its works riders o n each of th e three ma jor br a nds of tires Mich elin (Roc he and Falappa, Dunlop (Polen) and P ir ell i (Mert en s, plus Tardozzi wh en he join s in after doub tless wi nning the Eu ro pean ti tle by m id -year, a graceless piece of che rrypicking th at has earnt Du ca ti few bro wn ie points a mo ng th e impecunious priva teers making up th e Euroseries grids). This eac h-way bet may be acci dental, or deliberate, bu t what it has don e is to ens u re th at at least (Left) The Kawasaki uses Nissin sixpiston calipers and Ohlins suspens ion front and rear. Last year the team used Kayaba fork s, but excellent service support at the races by Ohlins ca used th e change. _ suffered at Doningt on by Polen and Roche. Instead, these were down to a lack o f oi l to th e gudgeo n pin, a p robl em su ffered by priva teers last season a nd resol ved by Carillo rods with a n oi lway drilled up th e shaft to the little en d. Rather lat e in the da y, the factory are now fitting rods fro m the ir Austria n su ppliers Pankl to this spec ific a tio n , wh i ch resolved th e p robl em. Bo rd i adm its to testin g titanium ro ds in search of reduced reciproca ting weigh t, but says that the rep lace me n t cost is too high for th em to be fitted to all engi nes. Only to th e trick ones, eh Massimo? . Talking of which, the SBK pa ddock is co nvi nced that Roche has a spec ia l q ua lifyi ng engine a t his disposal, whi ch is o n ly fitt ed for th e Sa tu rday timed qual ifyi ng, and is replaced for Su nday's rac ing by a nothe r, presumabl y longe r- lived un it. T h is tr ick improves on - his bike noticeabl y jumped away from Polen's out of th e slower turns at jarama. Bordi knows this: "We're still using 94x64 mm and an 888cc configuration," he says, "but th e next step will be a full IOOOcc engine based on the 502cc 4-valve single we have under development, which has a 70 mm stroke. We'll fit it to th e new chassis which Massimo Tamburini has designed for us , which has a better weight distribution and altered rear suspension," It also has a single-sided rear sw ingarm, a fact which will no doubt give th e ELF/ Honda patent law yers some potentiall y abortive wo rk, with a Fu ll Floater-type linkage and interestingly enough, the swingarm pivoting ou tside the cran kcases, rather than within them as at present, Whether the new one-liter 8-valv e desmo employing th is frame debuts at the Milan Show in motor certai n ly tak es three stro ng men abou t a 50-yard run to coax into life , a nd sou nds quite unlike any of the othe r Du ca ti .m o to rs in pit lane. Though Bordi d iscla ims the use of q ualifying mot ors , a nd a lso sa ys the rev limi ter is set at 11,500 rpm on the '9 1 motors , riders have let slip th e fact that th ey're now running th e 88&c engine to over 12,000 where nec essary - th e 95.6 mm bore, 920cc 'ju mbo ' mot or expe r imented last year has been set asi de in favor o f th e smaller unit, says Bo rd i. Com pressi on has a lso defin itely been rai sed , to aro u nd 13:1, whi le 36 m m inlets /3 1 mm exhaust valve sizes are employed (34/30 on th e 'stock' 8-val ve), th ough Bord i says he thin ks 35/30 may be a better co mp ro mise. Cam profiles are unch anged from last sea so n, but a n ew crosso:e r exha ust syste m di spensing with th e usual 'sta r ' (and unquest ionab ly based o n th e Bimota design for th e sa me en gi nel) has yielded a n extra 3 bhp a nd 500 rp m a t the top en d, as well as improving m idra nge performance, says Bordi, wh o al so admits to having done co nsiderable wo rk on reduci ng internal frict io n inside th e motor, in order to im prove engine accelera tio n - Roche's tr ick mot or sou nds espe cialy free-revving when bei ng warmed up. As Kawasaki 's Doyl e has remarked, Duca ti have achieved th eir cu rrent supremacy without ta king fu ll advan tage of the rules - th ough th ey are no w a t las t respec ta bly close to th e twi n-cy li nder weight lim it, which a rider o f Roche's small build further November, in time to be homologated for the 1992 SBK season, will doubtless depend on how close the opposition gets to th e all-conquering Italian bikes th is season. As things stand at present, Ducati won't need to bother with th e new bike just yet. (Righ t)Ya maha's effort in the series is still spearheaded by the OWOI. The 1991 model features a new radiator. one Du ca ti rid er is o n the right rubber . Smart move! So far , Pol en 's Dunlops a ppear to be th e ho t tip, just as in the 500cc CPs, but P irell i is right up there, while Michelin ru n ne rs are struggling with basically just o ne set of usa ble prod uc tion co mpounds, and a soft 'special' rea r (SC I860) which won 't last the distance, even th oug h the Miche li n men keep th ro win g it at people like Phill is a nd P irov ano, who no w kn ow better. Dunlop have made h uge strides in d urabi lity in the pa st year or less, and are deservedl y reaping th e rewards, especia lly with Pol en at the throttle end. Metzeler services some of the privatee rs a t the en d o f the field looking for a good dea l, but do esn 't rea lly have the product, while persist ent rumors indicate that Bridgestone is testin g new Superbi ke rea rs in j apa n at present - they don 't have on e right now - a nd are set to join in nex t season. Tha t' ll raise the ante ... Wh il e concentrating on th e weight and aerodynamics, Bordi has not forgo tte n th e Du cat i's engine, though winter devel opment was aimed a t im proving re liabi li ty rather than upping power. So for exa m p le a new grade o f a lum in um sourced from Alcan in Ca na da is now used in eng ine cas ti ngs, which he claims has comp letely so lved the vexed problem of cracked cra n kcases suffered last year by not o nly privateers, but also th e works team (Roche at Hocken heim). Crankcase l if e is va st ly in creased, a n d likewise p isto n s after a switch to Bri tish-mad e Omga s, which were no t to bl am e for the two race bl ow-u ps KAW ASAKI: High Hopes OSt consistent th M Phillissoon thechallengerhasworkse Ducatis far this season been Rob sing leton to ZXR750R Kawasaki, and indeed the gritty Aussi e led the World Championship points table briefly after the first leg at j arama , before being punted off at the first turn in the second race , thus regi stering his firs t DNF o f th e season th rough no fault of his or his newmodel mot orcycle, which has otherwise mi ghtily im p ressed so far this year. Kawasa ki op ted to design a completely new short-stro ke engine to go Superbike racing with this seaso n, and at 7lx47.3 mm, the R-type engine has a con siderable appetit e for revs whi ch resu lts i n the best-sounding fourcylinder bi ke in th e field, and makes quite a con trast with th e lu sty boom o f th e Du catis. Though it pulls fairl y well fro m 8000 rpm .u p wards, Phillis says he needs to keep th e engine in th e five-figure band to get competitive power, and redlines it at 14,200 rpm, with peak power of HI .b h p at the gearbox del iver ed at 14,000 rpm on the Kawasaki Au stralia d yno. That's the - - - - - - Continued on page 73

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