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Issue link: https://magazine.cyclenews.com/i/127291
denso comp uterized ignition, but as set up norm all y for Sn etterton the valve o pens very quickly fro m ' 7000-7500 rp m, making for a smooth transition in to the real powerband from SO Orpm O upwards. From there, the Yamah a just takes off, with th e engi ne accelera tio n between 10,000 rpm and the 11 ,750 rev mark at which maximum horsepower of 165 bhp is produced literall y mindboggling - ' th e revcou nter needle flashes ro und the dial quicker than the eye can see - that is, if you hap pen to be do ing anything so unw ise as not to be loo king at the road an d trying to ha ng on for dear life as the Yamaha gets into its rocket-powered stride! Hanging on for dear life is something you do a lot of in th e lo wer gears till you rea lize the sma rt move is to short -shift a t abou t 11 ,000 i n th e bot tom three ratios exiu ng a tigh t corner' like th e .Sneu er to n esses o r Mickey Mouse chicane, simply to keep the front whee l mo re or less in sem ipermanent contact with the ground. Last year 's Yamaha liked to wheelie, too - bu t not to anything like th e extent of this year 's bike, with its shorter swi ngarm and more rearwards weight bias, whic h reaches for the sky with the ease of an F-16 if you cra nk the throttle hard open at lower speeds. Un like so me rece nt works 500s, thoug h , the Yama ha is excep tio na lly stable in a stra ig ht lin e and ro und fast sweepers, thanks no doubt to the relat ively conservative steer ing geometry the bike adopts - a 26-degree head angle as tested is quite unusua l by today's raci ng sta ndards, mor e like a roa d bike than a racer, as too was the 10l mm of trail em p loyed with the o ffse ts filled . Rai n ey expe ri me nts constant ly wiih the chassis geo metry in race practice, usin g the offsets and eccentric inserts to vary th e. trail and . head angle, so th ere's no standard setti ng as suc h, but th e range of adj ustments offered by the Yam ah a is mu ch less extreme tha n the 22-24.5 degrees and SO-90mm tra il of today's average race bike, which similarly has a mor e fro ntal weig h t bias than the Yam ah a 's co nserva tive 53 /4 7% balance. The result of a ll this is a bike tha t can 't be described as nimble, but also isn 't twitchy or nervous either, whi ch has good traction at the expe nse of being front wh eel happy under accelera tio n in lower gears, and whi ch thanks to the excelle nce of the Ohlins suspension and its com p uterized setup - sadly not available for our test day , which is probably just as well since it wou ld have charted every one of my mistakes I - rides the many bumps to be found on Sn euerton's car-ravaged surface superbly. So when you hit one of those bumps flat out in fift h gear h a lf wa y down th e straig ht, th e Yam ah a just rides it wi th scarcely a shrug of the sho u lder , where a mach ine like the 'S9 Cag iva would have staried to tie itself in kno ts, tha nks to its steep head ang le an d minim al trail. Or agai n at th e lon g fast right-hand sweeper at Cora m, wh ere the 'S9 Honda NSR500 would hav e determ inedl y. headed for the bu shes under power thanks to its . inbuilt understeer, the Yamaha held a tight line as bid - thoug h it still ta kes some effort to stop the front end was hing o ut as the power is fed in once the corne r opens up. Bu t the differe nce is that wh ile the Honda would no t have responded to a get tough policy, for cin g the rid er to close the throttle to bring it back into lin e and thus waste precious tim e, the Yamaha will do what you tell It to do - o n ly at the cost o f some physical a nd me nta l effort. It 's th e same in slower turns the Yam ah a can ' t just be flopped on its side, th en fli pped upwards for accelera tio n like the dain ty-handl ing Suzu ki: it requires a conscious effort to pull it over into a turn, and then the same aga in 'in reverse o n the exit, perh ap s a trad e-off for that conservative. steeri ng geom etry and th e stable handling it produces. Sometimes, you can have t06 mu ch of a good thing. The least predictable part is the way the bike suddenly falls on its side o nce you 've heaved it over intoa slow corner - the tran sit ion is quite abrupt, and is not ideal , espec ially when tracks like ' J erez and Le Mans are starti ng to o utn umber the lik es of Salzburgring and Phillip Island I If th e Yamaha's low -speed handling is less than perfect, its poise in medium to fast co rne rs compensates for this, and its stability under braking is superb: all it takes is a rider brave eno ug h to find the limits, wh ich sure ai n 't mel But mu ch to my surprise, the actua l brak ing performa nce of th e bike was less than I expec ted, since the AP fo ur-pot calipe r and 320mm steel discs filled to the bik e for o ur test day had a very wooden feel, and needed a very hard sq ueeze to get effective sto pp ing power. T his is norm all y th e least of your prob lems, even with a 300 kph rocket sh ip, thanks to today's hi gh level of braking technology, and AP steel discs I' ve tr ied on o ther bikes work ed well. Maybe my extra weigh t compared to Rain ey is a factor (tho ug h it didn't seem so on hi s last year's bike I tried ), but overa ll the result was disappo in ti ng : th e bik e stops, but only a t the expense of' a lot of pr essure, which after a few laps caused my arm tos tart p umping up. Rainey' started the season wit h steel bra kes, till one cracked in the first (ra in-abo rted) race at Misano - he was lucky th e team was ab le to rep lace it for the fin al sp rint wh ich neu ed him overa ll. victory whereaf ter he used carbo n brakes for the most part of the rest of the year. But the World Champion prefers the greater sensitivity of the steel discs, wh ich leads me to be sure there was somethi ng wron g with the brake setup at Sneuerton - sens itive they weren't. Bad choi ce , ma yb e or ma ster cylinder size? Is this why Eddie Lawson op ts for six-p iston ISR calipers? But such criticism pales beside the Yam aha's trump card - its flexibl e friend of an engine, torquey and usable from low down, though surprisingly reluctant to rev hi gh: 12,600 rpm, and the V4 motor's all don e, unlike the Suzuki .and this year the H onda too wh ich have a consi derable overrev capa bi lity into the 13,000 rev range. T here isn 't a brick wall a t tha t engi ne speed like on the Cagiva, only tha t tne engi ne just sto ps ' acce lera ting and ho lds its revs without the power falling off. No doubt thi s is one secret to Yamaha 's relia bili ty - their em phasis on producin g more po wer low down and increasin g rid eability, rather than going for lots o f revs and a stratospheric overrev capacity. Effectivel y, what Yamaha has done is to move their powerband 1000 revs down th e scale, resulting in less wear and stress on engine components, without sacrificing performance - well , not too much in relative terms, anyway ! Faster th ough . the Suzuki and Honda ma y have been , it was th e Yamaha that took the titl e, and that speaks volumes for the bike that, like the Porsch e 911,has becom e justly recognized as the best a ll-ro under of its genera tio n. But wh ether that jack-of-all -trades ap proach to overa ll performance will be sufficient to ena ble Yama ha to hang o n to the titl e in 1991 remains to be seen, though havin g won th e champ ionship in 1990 with a bike that was 22 lb. heavier than the Suzuki, itself sca ling right on th e 500cc class limit. Yam ah a mu st be relishing the advent of th e new 2S6 lb. minimum weight rul e. That wei ght pen alty was significant factor in the YZR's lack of performance com pared to the Honda I and Suzuki this seaso n, yet Rainey still wo n th e title thanks to the bik e's stable handling and sweet power delivery; especially in the midran ge: usability! defea ted po wer. ,8 Thou gh the extra po unds may hav been a factor in the heavy handlingj I discove red at Sne tter ton, thi s hasi} n:ver been anythi ng new with th ~ YZR, wh ich has won four titl es thank~ i} to Yamah a 's in sistenceon building a ) rugged bike that will fini sh races rath er than a lightweight o ne that won 't. m r> take qui te some combina tio n of rider r and mach in e to stop th em making it ) ai a fifth in 1991. a ' Specifications Yamaha YZR500 Engi ne type Water-cooled reed valve V4 two-stroke with twin contraro tating cranksha fts and drum-type electro nic power-valve Bore x stroke 56x50.6mm Displacement :; 498cc Horsepower 162 bhp at 11 ,750 rpm Carburetor Ax35.5mm Mikuni dual-body flat-slide Igni tion Nippondenso pre-programmable computerized CD! Gearbox 6-speed extractable Clutch Multiplate dry (7 friction /6 steel) Chassis , : Aluminium twin-spar (fabricated) Front suspension Ohlins inverted telescopi c forks (42 mm stanchions) Rear suspens ion , Fabricated aluminum swingarm with Ohlins unit/titanium spring and rising rate linkage .Head angle 26 degrees Trail. 97-106 mm depending on offset Wheelbase 1395 mm Weight 125 kg. with oil/water, no fuel Weight distribution _ 53/47% Front brakes 2x320 mm AP steel discs with four-piston AP calipers Rear brakes lx2oo mm Yamaha disc with two-piston Nissin caliper Front wheel/tire 12/60-17 Michelin radial on 3.50 in Marchesini wheel . Rear wheel/ tire IS/ 67-17 Michelin radia l on 6.00 in Marchesini wheel Top speed : 310 kph (at Yamaha test track) Year of construction , . .... . . ...... . . . . . . . . . . . ...• . , 1990 Owner ... . . Yamaha Motor Co., Iwata , Japan - leased to Marlboro Team Roberts, Amsterdam , Holland --