Cycle News - Archive Issues - 1990's

Colin Edwards II's Yamaha YZF750 (Left) Form idabl e peak power from the 2o-valve engine, and the quick transition Into It, makes gear se lection crit ica l on the Yamaha. (Right) Wheelspin made th e VZF a ch all enge exiti ng any of Mugello's four chica nes . 18 A choice of two different glorio us so u nding tit anium ex haust syste ms, each w ith a haunting wail at high revs, help deliver th is vi vid power. One is equ ipped with the EXUP exhaust valve and used for faste r tracks to allow th e bike to be tuned for top-end power without being too peaky, the other without this for use on tighter courses. Still, th e v ivid power delivery isn 't tam ed , 'even th ough the works bikes use the variable-len gth carb tr umpets to help fatten midrange and smooth out power deliver y th a t Bel garda tuner Beppe Ru sso (wh o loo ks aft er th e w orks engines, too) has been de veloping since last season on Mere galli's bike. But pickup is amazi ng . Th e wa y the needl e scoo ts round th e tacho d ia l delivers acceleration that is even more dramatic than the punchy, lighter Ducati - and impress ive, too . Only, it's no t such usable power - or as forgiving. You can mak e a mistake on the Ducati, like gas it at too low revs or hit the wrong gear for a tum, and it'll pardon you . The Yamaha requires total commitment. You must take care to be in the right gear at the rig ht time, always maki ng the engine rev high to p roduce its imp re ssive power output. This means u sing the gearbox qui te hard, wi th its rather m echanical, slightly notchy action . Despite this, the ge arbox works okay, and of course has a s p ee d- s h ifter h ooked up which you ha ve to forc e yourself to hit abo ut twice as often as with the Ducati to keep the Yamaha m otor working in its relatively narrow 3000-rpm-wide optimum powerband. The bottom line of all this is that the Yam aha is a missile in a straight line, a fact confirmed at Mugello wh en one of the stars of the future, testing the Fogarty Ducati, obligingly ou tbraked me into the last tum, got the jump on me out of it as the Yamaha did its usual party trick I'll tell you abou t in a moment - then got gobbled up tw o third s of th e way d own the pit straight by the YZF, allowing me to draw level with him as we headed into tum one. The Yamaha's metal Nissin brakes, new for this season, have good bite from their six-piston calipers; but not as much sen siti vit y as the equival ent Brembos. One-finger braking is not an op tion, becau se you need a good squeeze to get an y resu lts o n a bike that a t 347.6 pounds, is right on the '95 four-cylinder .weight limit. Still , I managed to ou tbr ake the even-lig hter Du cati into the first turn - onl y, I ou tbr ake d m yself as well, running way too wid e and getting passed on the way out! Dam - no works contract ... Still, by the end of 20 laps or so I was coming to terms with the Yamaha 's fiery ' engine performance, even if the inst ant response from the ligh t-switch thr ottle . took a lot of getting used to. But gettin g hard on the gas exiting any of the quartet of Mugello chicanes was an invitation to get the rear Dunl op spinni ng as it tried to hook up , which ma y be all part of life's rich pa geant fo r th e likes of Texan road racers like Colin and Kev, but for li'I 0 1' me is an acquired tast e. Especially when what happens next on the YZF is a power wobble that flaps the bars in your hands as you' re leaned over in the middle of a tum, while the Yamaha pushes the fron t wheel toward th e outside of th e track in a di spl ay of power understeer that I never felt with the same chassis riding Pirov ano's or Casoli' s bikes. Phew! Add in th e fact that the bi ke feel s surp risingly top heavy, and yo u h a ve a p hy s ic all y demanding p ack age tha t mu st have taxed the rid ers' stamina ra cing it twice a da y at each Superb ike rou nd . Colin has the bike se t u p so tha t it steers into a turn ve ry fast, .which his distinctive ridin g position - upper body far forward over the tan k and elbo ws bent backwards .:only accentua tes. Yet in spite of wha t feels like a tall rear ride height and shortish 55.5-inch wheelbase (the swingarm was slightl y len gthened com p a r ed to ' 94, a n d its p ivot is adjus table vertically for th e first time), the Yamaha is hard to change d irection with quickly in turns - you need a lot of mu scle to flip it over from side to side in a chicane. This is a strong-minded bike w ith a wi ll of its ow n, wher eas Carl ' s Ducati felt less extreme and more riderfriend ly, in handling as we ll as engine perform ance. The bot tom line from all this is that the YZF is both daunting and demoralizing. Daunting, because it' s even more of a mi ssile in a s traight line than th e Belgarda bikes I' ve,ridden in th e past, but d emo ral izin g becau se the lightswitch p ower d elivery means getting the engine's mega-power to the ground requires carefully d ialed-in su sp en sion and a' critical choice of tires - and I lost out on both counts. Former right-hand man to Kel Carruthers with King Kenny a nd Fast Eddi e on the title-winning Yamah a 500 ,GP team , then more recently Lawson and Kocinski' s race engineer with Cagiva, Fiorenzo Fanali explained why when I stop pe d to whin e at him abou t the handling. "You' re riding th e bike the way Colin had to race it ear lie r thi s ye a r," sai d Fan ali, "because the tires you ha ve are early- '95 English Dunlops that we had to use at the start of the season. At least you can experience the kind of problem he had to handle while Dunlop Japan wer e get ting ba ck to normal after th e earthquake! In fact, for Colin the biggest problem wa s the front tire, because he d o esn't like a s tab le bike - not like Nag ai, wh o rod e more smoothly like I think is necessary with Superbikes. He pr eferred more trail and stability, ju st like Eddi e Laws on. Col in 's s ty le is maybe better suited to 500 GP, because he p ref ers to have t he bike m oving around a lot, so he can fee l how the front tir e is behaving - it's hi s biggest concern. He likes th e bike to feel nervous, to change direction very quickly in the chicane . YamahaYZF750 Specifications Engine Liquid-cooled. DOHC . in-line four-cylinder four-stroke wit h five valves per cylinder and central chain camshaft drive Bore x stroke 72 x 46mm Displace_ 749cc Output ' '" Over 160 bhp at 13.800 rpm Compression ratio 13.2: 1 Carburetion ,(4) 39mm Keihin flat-slide Ignition _ Digital electronic COl (non-programmable) Gearbox ... . .. .. ..... . ....• . . . .. . .. .. .. .. ....' 6·speed Clutch ...... . .. . . . . . ... . . .•. . ... .. ... .... . . . . . . . . .Multiplate dry (8 metal/9 friction ) Chassis Aluminum twin-spar Deltabox Suspension Front : . . .46mm Ohlins inverted telescop ic forks Rear Fabricated aluminum swinganm with rising-rate linkage and single Ohlins shock Rake/trail , .24°/98mm Wheelba _ 55.5 in. Weight _ 347.6 Ibs. without fuel tank/with oil and water Weight distribution, front/rear '. ' 53/47 % Brake. Front Dual 320mm Ntssln cast -iron discs with six-piston Nissin calipers Re a r .Sinqle 192mm Yamaha steel disc with two-piston Yamaha caliper Wheel./ tires Front 125/70-17 Dunlop KR106 radial on 3.75-in. Marchesini wheel Re ar 185/50- 17 Dunlop ER108 radial on 6.00-in. Marchesini wheel Top speed . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . • . . . . 181 mph (Hockenheim) Vear of manufacture 1995 Owner Yamaha Motor Co.. Iwata. Japan

• Cover