Yoshimura Hayabusa X-1 - Heavy Bus

The Street Version Of Yoshimura's 200-Horse Formula X Hayabusa Racer Stops Wherever It Wants

Photography by Hiroshi Sato, Kevin Wing, Phil Masters

Well, what would you do in the off-season if you worked for Yoshimura R&D U.S. and found a Suzuki GSX1300R Hayabusa lying around? You'd ransack the candy store, that's what, especially if your pipeline to Yoshimura Japan was expectorating tasty chunks of Hayabusa Formula X racer. The Formula X bike not only won its class at the last Suzuka 8-Hour, beating all sorts of Yamaha R1s and Kawasaki ZX-9Rs, it also qualified on the tail of Noriyuki Haga's factory Yamaha YZF-R7 in the process, and finished 12th overall. Hai! It's a little bigger and heavier, but you can get more power from 1300cc than you can from 750, can't you? Let's see, that's, ahhh, 550cc more-very damn near a GSX-R750 and a 600. Now all we need to do is find somebody crazy enough to ride it. Where's that Gobert guy?

In the land of the rising sun, Fujio Yoshimura-son of Pops-believes in racing what people can buy, not just exotic factory superbikes. Hence Yoshimura's Hayabusa X1-R-or "Heavy Bus" as Yosh mechanics soon dubbed it. Very commendable.

Meanwhile back in Chino, California, at Yoshimura R&D of America Inc., just because you're Mat Mladin's crew chief by day-like Ammar Bazzaz-doesn't mean you're immune to the lure of highly cool toys. Co-conspirator and Yosh marketing guy Doug Wells has a full-blown '86 Yoshimura superbike in his living room and a bad hardware bug. Wells gave up a job piloting tourists to his native Bahamas to fondle hardware at Yoshimura. When an innocent, box-stock Hayabusa somehow found its way into the shop, no way was it going to escape unsullied. It had no chance.

Seeing as how an unmolested 'Busa already makes a reasonably frisky 160-ish horsepower and 99 foot-pounds of torque, Ammar and the kids decided not to emulate the Japanese Formula X racer too closely in the engine department. (At one time the racing 'Busa made 225 horses, but tires wouldn't live under it so it was "detuned" to around 208-barely enough to get out of its own way.) What you're looking at here, believe it or not, is destined to be a streetbike at some point, so Yosh went with a mild engine tune-only 182 horses and 108 foot-pounds of torque. Stage One billet cams, a little porting, 12.5:1 forged pistons, Carrillo 4340 rods, that type of thing, move the power peak up to around a nice, safe 10,500 rpm and the torque peak to 7500. Runs on pump gas, Ammar says, but what's that sweet smell?

Since they were in there anyway, Yoshimura yanked out the stock engine counterbalancer-though Falicon did such a nice job polishing and balancing the 2.5-pound-lighter crankshaft you'd never notice.

MoTeC (www.motec.com) of Australia, having already proved itself in auto racing, is moving into bike electronics and provided its mondo-megabyte military-spec M48 engine controller, which directs the stock fuel injection. MoTeC also makes the bike's data-logger, which displays comprehensive real-time data on the LCD dash while storing all manner of information for later reference. Since the logger uses the same sensors as the engine controller, all that connects logger to controller is a two-wire serial connector; simple and light.

Heck, with MoTeC's lambda sensor telling you the exhaust's oxygen content at any given rpm, under any load, you really don't need a rider to help you get the jetting perfect, do you, Ammar?

Wrong again. A good rider is still critical to making the bike work right, and a guy like Aaron Yates, who's particularly good with carburetion since he worked on his own for so long, is able to use the in-flight dashboard's lambda display (lower left on the LCD dash) and throttle position indicator (lower right) as another really useful tool in making the engine run as hard and smooth as possible.

Proven rock-steady in Formula X, there's no reason to fool with the bike's frame, really, except that you can. As on the racebike, then, Yosh added a GSX-R superbike swingarm-which shortens the wheelbase 25mm-and a kit hlins fork carried in kit superbike magnesium triple clamps (30mm offset keeps the front wheel from scraping the fairing's chin).

Ammar was a Harvard-educated mathematician before the bike bug hit him 11 years ago, at 20, and he enjoys nothing more than figuring out which combination of hlins spring and dampers is needed out back to make the Yosh swingarm linkage work. Less progressivity, or rising-rate, is the way to go on the track; that keeps damping consistent throughout the stroke.

Nice of the Yoshimura people to truck their completed X1 out to the track for us to get a test ride, wasn't it? Who wants to go first? Listen, why don't you go? I feel fat in these leathers, a little bloated.

From the beady tip of its 8-Hour headlight to the smooth blended-in-ness of its LED taillight, this bike sitting on its stand reminds you of a nicely mounted, well-fed Carcharodon: You don't want to get too close, just in case it suddenly reanimates and starts snapping. Even after losing all the street equipment and adding the Ti pipe, Marchesini wheels, etc., the thing still weighs just under 500 pounds full of fluids. The tail-section/seat sits two or three inches higher, too, for cornering clearance.

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