Cycle News - Archive Issues - 1990's

team in 1991, then to [ochen Schmid in '92. These bikes only sha red about 10% common parts with the YZR, says Yoda (and none at all with the new TZl 25, in case you wondered - not even the prototype that blitzed the Japanese 125cc title in 1993, though I bet the works cylinder would fit right on), but Harada's World Championsh ip-winning bike was a direct development of Schmid's '92 bike, which I rode a year ago at Hockenheim. That prepared me for the culture shock of riding a bike that, b y comparison with its works Honda and Aprilia rivals, is all mid-range, has a relatively narrow power band and sudden power d elivery, with no real appetite for high revs. Set up a little rich on a sunny afternoon, after a cold start to the press-day activities, it might have been a li ttle down on revs, bu t even so, the 13,100 rpm, which was all tha t regis tered on the tach while neg otia tin g Fu kur oi' s m ile-lon g s traight, were rat he r grudgingly delivered . N o rm al maxim u m over-rev is 13,500 rp m.isays Yoda, bu t . tha t' s over 500 rpm less than the '93 Hondas o r the rota ry-valve Aprilias, making the choice of internal ratios for the side-loading gearbox crucial at every circu il Even so, this wouldn't be such a big a deal if there was more power low down but, just like Schmid's bike a year ago, the Yamaha won 't really carburete below 8000 rpm, at which point everything starts to happen very suddenly as it begins to struggle onto the pipe. Then from 9000 rpm upwards, the engine takes off and builds revs very fast, up to the maximum power mark of 12,500 rpm, at which point 89 hp is available at the gear sprocket, which is 3 hp or so more than last year. After that, the power delivery trails off, so the trick is to try to keep it motoring in that envelop e of mid-range su perpower, where the Yamaha does feel at least as strong as its riva ls - but only there. This relatively narrow power band, by modem standards, means you have to use the gearbox a lot. You end up coming to appreciate Yam aha's own speed -sh ifter that's fitted to th e bike, enabling you to fla t-change smoothly wit h the throttle wi de open to save every precious rev yo u've managed to la y yo u r hands on. That system is derived from the Telle r t CTS design which [ochen Schmid introduced to GP racing last year on his TZM Yamaha, but this one has a smoother change, without the harshness of the crs, with a variable cutout time for the ignition in every gear. Still, it doesn't like being used on either part-throttle or unless the engine's pulling at least 12,000 rp m, and isn't so clean in the lower gears. Bu t then you have no business short-shifting the Yamaha in the first place - wide open, and with max revs in every gear is the only way to combat the lack of topend power. A t th e other end of the sc ale, the Yamaha is surprisingly slow to come on strong. It feels as if the guillotine power valve has a rather steep operating curve, though this may be alte red by fitting a d iffe ren t EPR OM chip to the contro l box. The power valve is linked to the operating curve of the digital ignition, itself EPROM-adjustable, bu t there 's no link to the th rottle position of the 39mm flatslide Mikuni carbs, as there is on the NSR250 Honda, for example. It may be the absence of this link whic h is a factor in the rather sudden low-rp m delivery. However, those very trick and very expensive magnesium-bod y carbs, with their ang led floatbowls to offer a deadstraight hit at the reed-valve boxes and inlet tract, have electronic powerjets whose timing can also be al tered by Now Available Through Cycle News Video Theater 1993 ISLE of MAN TT - A Place In History (#940 ) Eighty-six years after the first TTtook place on the Isle of M there seems no limit to the numberof an, fans whowant to be partof an event which is now totally unique inthe worldof motorsports. They come - over 40,000 of them in 1993 - from all over the world to see far more than the most thrilling motorcycle sport anywhere. They wantto enjoy high speed racing on real roads where you can watch from just a fewfeet away; to personally sample the most demanding course in the world on the notorious"Mad Sunday"and other non-racedays; to take part in a massive festival of motorcycling wtth everything from beach races to street parties, bungee jumping, bike rallies and air displays; and of course to follow TT heroes like Joey Dunlop, Nick Jefferies and Phil McCallen. The extensive race action In this videocelebrates Joey's historic 15th TT victory, Nick's first TT win, Phil's Senior victoryand the other thrilling solo and sidecar races. Thisvideo includes over 1-112 hours of action, while on-board cameras put you in the seat with the top bikes and sidecars - including, for the first time, on-screen RPMand speed data from McCallen's RVF Honda. 100 minutes from Duke Video USA. "- 0'> T'""'i 23

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