Cycle News - Archive Issues - 1990's

GRIDING IMPRESSION ~ 1994YamahaYZF750RF "- 00 H Q) ~ Q) u Q) Q 6 hen was th e la st time Yamaha won' th e AMA Superb ik e Na ti onal Championship? If yo u sa id 199 1 w ith Thoma s St evens at the helm you 're right. That wa s only two ye ars ago, but for Yamah a it seems a whole lot longer. The year follow ing Stevens' title-w in- . ning performan ce, Kawasaki sna tched the numb er-one plate awa y with recently crowned World Sup erbike Champion Scott Russell providing the th rottletwistin g. In 1993, Doug Polen and his V~ tw in Ducat i 888 breezed to victory over Kawasaki.riders Dal e Quarterley and Miguel DuHamel. After ha ving relished the swee t taste o f a s u perbike cham pions hip for th e first tim e in '91, Yamaha quickly grew tired of playin g second-fid dle to the Kawasaki and Ducat i team s. 50 they d id somethin g ab o u t it - th ey completely r ed esigned their racebike, and what they ulti mately came up with is the all. new YZF750R. N o t on ly is this good news for Team Yam a ha rac er s Jam ie James and Co lin Edwards II, it's also extremely good news for you - for a cool $9799 yo u can buy basically th e same bike James and Edwards will rid e in the 1994 AMA Superbike National Championship. The YZF750R is Yamaha's firs t stateof-the-art production " racebike" si nce t h e ' 89 in troduction of the p op u lar FZR600R. (Yamaha already has an allnew YZF600R in the wo rks, but it won't be seen in the U.S. un til mid-'94, as a '95 model bike. The YZF600R is already ' available in Europe). The last up-to-d ate 750cc Yamaha production "superbike" was the FZR750, .w hich ma de its first ap pearance in 1987. The YZF750R is based on the race team 's YZ F750SP su perbikes, which mad e their track debu t earlier this year at Wiscon sin's Road America, for the fifth round of the Na tional Road Race Series. The 19-year-old Edwards immediately went out and qualified fastest on the new bike, but later crashed du ring the race while running second when he and Ducati's Pascal Picotte tan gled on the second-to-last lap . The other SP, ridd en b y James, finished third behind Polen's winning Ducati and DuHamel's Kawasaki ZXR750R. It wa s at Road Amer ica that Jame s commented on his new Vance & Hines . YZF750SP, which repla ced the aWOl : "It steers good and it sticks in the turns. It's really the perfect bike. The aw was a c ompr ~,m ise . This engine fee ls stronger... James and Edwards we nt on to finish fourth and sixth, respectivel y, in the series. Perhaps the new SPs arrived five races too late . A t leas t James a n d Ed wards wo uld like to think so. Never the less, the "street-Iega l" YZF750R that will be hitting showroom floors in Jan ua ry will, of course, be somewhat different tha t the SPs ridden by James and Edwa rds, but the found ation is the same. The new YZF750R is powered by a 749cc, slant block, parallel four-cylinder, five-valve-per-eylinder (three intake and tw o exha us t va lve s), liquid -cooled, DOHC Genesis engine, a direct descend ent of the Yamaha awol Superbike . Large-bore 38mm (39mm on the SP race bikes) do w nd ra ft Mikuni carburetors feed in to ne w, straigh t, narrow ports. Fuel is force-fed into th e carbs via an electronic fuel-p ump located insid e the gas tank. To accommodate the stra ighter ports an d redesigned combustion chamber, the ang les of the valves have been slightly chan ged . The combus tion cha mbe r vo lu me is slightly smaller in the YZF750R/SP's e ngi ne as compared to the aWOl 's ' engine, 15.3cc to 13.1cc. Yamaha also lighten ed u p th e crankshaft, and the EXUP (Exha ust Ultimate Power-valve) system is still used . The EXUP is a small, microcompu ter-eontrolled valve, or flap , that is located between the header pipes and the muffler of the 4-into-1 exhaust sys tem. At full throttle the valve opens to its maximum, while at idle, the valve ope ns only slightly. The EXUP va lve not on ly co ns ta n tly a n d automatically adj usts or "tun es" the exhaust system for o p timum performance, it also reduces exha ust note, especially at idle. Th e YZF750R is fitted with a sixspeed transmission, but, un like th e close- ratio tranny found in the SP race bikes, the R's tra nsmission uses wi der gear ra tios th at are better s ui ted for street riding. The lightweight, alumin um Deltabox frame feat ures a removable a lum inu m subframe an d is designed to be extremely r igid and smaller overall than the aWOl chassis. The smaller frame translates into a fairly short 55.9-inch wheelbase for quick er handling, but according to the folks at Yamaha, overall stability has not been sacrificed. Keeping th e ov e rall weight down was of prime concern. In addition to using an aluminum mainframe and subframe, weight was re d uced by using alum inum handlebars and triple clamps; newly designed aluminum cast wh eels; hollowed-out front (22mm) and rear (28mm) a xles; lighter forks; by installi ng shorter and lighter bolts, and using an assortment of aluminum-eonstructed stays and brackets. Just about every part on the motorcycle was made lighter. The claimed overall d ry weight is 428 pounds. The front suspen sion is handled by . an in ve r te d 41mm telescop ic, coil spring/ oil fork, and the back end is handled by a single, gas / oil shock, risingrate link suspension system. Both front and r ea r suspensions are full y ad jus ta ble for sp ring pre-load , and rebound a nd compress ion damping. The rear shock a lso fea tures a remote reservoir, and the tru ss-type aluminum swinga rm is designed to be lightweight and extreme ly rigid . Also, to improve rigidi ty up front, the width of the triple cl amp s is narro w er so there is less chance of "fork twisting. " Wheel travel up fro n t is 4.72 inches w hile th e rear boasts 5.12 inches of travel. A lot of atten tion wen t into the YZF's braking sys tem. Up front, super-powerful, 320mm du a l fron t ro tors with sixpiston calipers have been installed; in

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