Cycle News - Archive Issues - 1980's

Bimota Superbike (Continued from page 11) Birnota had to narrow . th e powerban d a nd go for revs - a nd lots of th em. The power del ivery is fierce. Though i t' ll trickl e off fro m a standstill just like a mod ern two stro ke race r does, no t mu ch happen s till the read out o n th e T DD di gi ta l tachom eter indicates 8000 rpm and the Bimota starts to " ca rbura te" if yo u ca n use th at term for a bik e fitt ed with EFI ! From 9500 rpm upwards there is trul y exp losive horsepower o n tap. But since the. rev limiter o n the Weber/Marell i EMS is set a t 13,000 rp m, a nd peak power is deliv ered at 12,200 rpm , you have a lmos t exac tly th e sa me po werb and as wi th a GP two-stroke - witho ut th e ben efit of a power valve system to smooth o ut th e delivery! The result is lik e riding a mod ern GP bik e with th e power valve di scon nec ted. You mu st try at all costs not to let th e revs drop too low, so th at yo u don't hav e to cope with the sudden tra nsitio n betw een power off and power o n. You can' t rid e th e Birnota lik e, say, a V-four Honda, with its much wider spread of torque and far easier power delivery. 'T he It al ian b ik e is a h ighl y-strung, excitable La tin lovely, compared to th e more in scrutabl e, p lac id-but sti ll-po werful J apan ese bike. This mak es use of the gea rbo x much more o f a key factor th an yo u might otherwise expect wi th a four-stroke, hen ce Bim ota's decis ion to alter th e internal ratios to obtain better use of the availab le power. It also means th at cha nging up without use of the clutch is desirab le, to make sure th at not a single vital rpm is lost, though to my surp rise the Bimota crank still has a lot of flywheel effect, so th ere's a fair degr ee of in erti a to keep th e sho w on the road , revs-wise, as well as for purposes of engine braking not that th e massive and highly effective Brernb os need a lot of help. Having said that, I ca n think of anoth er bit of dat a they co u ld usefull y slot into the co mprehensive disp lay on th e u ltra- light, ca rbo nfiber TD D unit, which in addition to thousands of rpm across the top, also advises the rid er of su ch fascina ting deta ils as th e air pressure inside th e airbox, fue l co nsump tio n , wat er and oi l temperatures a nd rpm in hundreds in the bottom, righthand corner. All this is overkill , and Fal appa cheerfu lly admits he almost. These cool air ducts were tested for the f i rst time at Rijeka. never looks at anything excep t th e 1000s of rpm, which I personall y found much harder to read than an old-fashioned, analog ins trument with a need le, which you can read instinctively simply by its position on th e dial, without looking at the numbers. New is not always better. However, a digital readout to tell you what gear you 're in would be useful , as with the ratios so clo se together and the engine note scarcely varying between ratios, it 's hard to tell if you're in £ifth or sixth co m ing past the pits. If the YB4EI R is much more difficult to ride than I expected on acco u nt of th e hyper-dev el oped nature of th e engine, this impression is heightened, rather th an lessen ed by the EFI. Wh ereas o n th e YB4EI roa ds ter th e Weber/ Marell i system resu lts in a smoothe r, more deli cat e a nd lighter th ro ttle, whi ch pe rm its a grea ter deg ree of precisio n iiI use (espec ia lly in pa rt ial openings), the race bike is quite the opposi te. Not o nly is the action stiffer, presuma bly o n acco unt of the stro nger spring needed to co u nterac t the su ctio n effect of th e race motor, but the abru p tness with whi ch th e power co mes on in part- throttle situations mak es the Birnota a ver y ha rd bi ke to ri de around slow co rners off the po werband - or, I would im agine, in the wet , as T ardozzi found to his cos t in New Zealand a t the end of last seaso n wh en he lost the World titl e. If you close th e th rottle fully or partl y, like in Rij eka 's tri ck y hairpin which tightens up as yo u , exi t it, th e eng ine chimes back in aga in very sudde nly, making a jerk y progression a ro und slo w co rners hard to avoid. Again, it hasn 't the flexibility o f a H onda , a nd . th e sudden power delivery also makes it easy to unhook th e rear tire, as I d iscovered more th an o nce comi ng o ut of th is slow turn. Bu t the coro llary of this hard- tolive-with power deliver y is th a t o nce poin ted in a reasonably stra ight line, and with the engine howling in five D igital instruments keep tabs on all v ital functions. i n cl ud ing rpm. figures, the Bimota simply rock ets forward, wr iggling and weaving as great gobs of power are unleashed to the rear Michelin. Scaling right on the Superbike class minimum a t 165 kg. (363 lbs.) dry , the Bimota's 132 bhp doe sn 't give it quite suc h a dramatic power-to-weight ratio as a modern GP 500, but not by much . Acceleration is trul y impressi ve, while o n top speed this 750cc fourstro ke wouldn't be giving a lot away to a 500cc two-stroke, having been timed at nearly 170 mph at Brainerd, a nd 180 mph expec ted as gea red for th e long straights of Hoc kenheirn, Germany. One reason for th e noticeable degree of flywh eel inertia is perhaps to obtain this top speed , but whatever th e case, th e Bimota is certa in ly amongst th e fastest, if not the fastest bike in the Superbike class at present exce p t for that am a zing Du cati . .. It 's al so a lmos t certa in ly th e besthandling, a fa ct whi ch ena b les Falappa to make hi s breathtaking runs up th e in side of th e leading group of riders with impunity. A key factor here is the su perb Brernbo brakes, which have lo ts of feel but the abili ty to stop a truck if used to their maximum potential. Braking · from the YB4's top speed (around 160 mph on Rij eka gearing) into th e first turn past the pits, I eve ntua ll y wound myself up to doing so at th e 175-meter board for the third-gear Ieft-hander, though wa tching Falappa later, he was waiting a good 25 meters more. Fantastic. Yet, T h e Bimota YB4EIR Superbike employs the o lder. Yamaha FZ750 engine. ra t her than t he newer FZR. and w raps it i n huge twin aluminum spars. hav in g waited that long to th ro w o ut th e an chors, you ca n do so secure in th e know led ge th at th e Bimo ra chassis a nd Ohlins suspensio n will get yo u arou nd th e ens u ing co rner as if you were o n ra ils. Big Ears' Marzocchi forks felt less responsive by co mparison , being too stiff on co m pression so th at I co uld n' t feel th e roa d a nd wh at th e fro nt tire wa s doi ng in the same way as wi th the Ohlins, a nd th ey a lso mad e th e bike feel a b it h igher in fron t, with co rres pon d in gly slo wer st eering . The Ohlins a re, of co urse, a nother .factor in mak ing fu ll use of th e Brernbo's massive braking potential, never deflecting th anks to . th eir sturdy 53mm ou ter upper tu bes, and 44mm low er inner s, so th at th e su spension keeps working a t all times to full advan tage. It 's th e first time I've ever ridden a bike fitted with th e scarce Swed ish-ma de forks, a nd now I can begin to appreciate w hy so m an y team s a n d r iders co ns ider th em The Business. At th e rear, both Marzocchi a nd Ohlin s-equipped bikes felt eq ually good, especially in th e last co rner at Rijeka, a 270-degree left where you have to gas it ha rd to get maximum drive down the straigh t just as you ride into a litt le dip. The Bimota never thought twice about how to ha nd le this awkward undulation in th e road surface, met while th e rid er's cran ked over and th e suspe nsio n already partiall y co mp ressed by the wid e-open throttle: th e rear end just co mp ressed so me more, withou t . freezin g or bottomin g ou t and caus - in g a slide , e na blin g the fierce ho rsepower of the engine to catap u lt me down th e 'stra ig ht again; off for anoth er lap in vain pursuit o f Fal appa o n th e pro tot yp e T esi . . . If I th ough t Falappa was a star after watch ing him terrorizing th e more expe rienced opposi tion aboa rd the Birnota thi s seaso n , after rid ing the bike he does so wit h, I know he is! The ultimat e version of th e YB4 lin e is a fast , fierce motorcycle whose exp los ive p ow er de livery is o n ly made usable by its fi ne ly-hone d chassis. Even so, it's a bike that few riders would take readily to ex trac ting th e most from week after week, so perhaps it 's just as well ·tha t Fa lappa's road racing experience is so . lim ited. That way, he doe sn 't kn ow how much easier it is to rid e a H onda! T o ach ieve what he has done on a bike tha t is so diff icult to ride is a tru e mark of Fal appa's tal ent; no wonder o the r team man age rs are already cas ting covetous eyes on the rid er wh o co uld well be one of th e sta rs of road raci ng at th e high est level in th e 1990s. The thought of him o n a GP 500, esp ecially a works V-four, sets th e taste buds tingl ing. At the same time, Bim o ta ha s shown by th e way th ey'v e developed the FZ motor, a nd have succeeded in harnessing its exp losive power su ccessfully, that th ey still have few riva ls in th e black art of cha ssis design. Together, th ey and Fal appa will represent stiff co mpe titio n in whatever field of raci ng th ey pl an to move into in th e fut ure. • Bimota YB4EIR Engine type DOHC, water-cooled. transverse. in-line . four-stroke four 68.3 x 51 .5mm Bore x stroke Displacement 749cc Compression rati o , 12:1 Fuel / ignit ion Weber/ M arell electronic EFI /EMS Horsepower 13 2 bhp Torque N /A Valves per cy linder Five Lubrication Oil . wet sump Redl ine 13.000 rpm Primary drive : Gear Final dr ive Chain . Final dr ive ratio N /A Frame Aluminium twin-spar Rake . . ; 24.3 degrees Trail 3 .92 in. Front suspension Ohlins . inverted telescopic forks Fork tube diameter 44mm Fron t wheel travel , , N/ A Rear suspension Swingarm with ris ing rate li nkage and monoshock Ohlins un it .Rear wheehravel N/ A Front brakes Twin 320mm Brembo discs with fourpiston Brembo cal ipers Rear brakes Sing le 230mm Brembo disc with two-p iston caliper Front wheel 3 .50in. Marchesin i Rear wheel 5.50in. Ma rchesin i Fron t t ire 12/6 0- 17 M ichelin radial slick Rear t ire 180/67-17 M ichelin radial slick Claimed dry weight 363 Ibs. N/ A Overall length Overall width N /A Overa ll height N/ A Wheelbase ' 54.8 in. Seat height N/ A Ground Clearance : . N/A Fuel capacity N/ A Top speed · 170 mph (as timed at Brainerd. MN) Manufacturer Bimota SpA. Rimini. Italy 37

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