Xreme Measures

Even with its bodywork on, the Graves Motorsports Formula Xtreme bike bears little resemblance to the stock Yamaha R1 parked nearby. You even have to look close to see the "50 percent by volume of the original frame structure" that must be retained according to the AMA rulebook. The engine looks familiar; its surroundings definitely don't. And what lurks inside the stock cases is anybody's guess.

You see, Chuck Graves--proprietor of Graves Motorsports, which runs the official Yamaha Formula Xtreme team with riders Damon Buckmaster and Aaron Gobert--is a tinkerer. And if the rules allow--or, more specifically, don't disallow --something, you can bet that the industrious team owner is hard at work in his shop experimenting and testing the limits of those rules. Graves, a Formula USA champion when that series had a run-whatcha-brung format, was at the center of the AMA FX controversy when the team ran its R1/R7 hybrids, and you could argue that he is largely the reason the 50 percent rule exists.

About the Bike
Most of us, when building a production-based racebike, would start with said streetbike and start removing what is unnecessary for the business of getting around a racetrack quickly. Graves, it would seem, takes the opposite tack, using only what's required as a starting point. For the Formula Xtreme engine, that means a stock crankcase, cylinder block and cylinder-head castings--what you do to them and what you put inside is all fair game.

Additional displacement--cubes that aren't allowed in the Superbike class--is the centerpiece of the typical Formula Xtreme bike, and these Yamahas are no exception. Depending on the track, Graves endows his R1s with a stroker crank, bigger pistons or some combination of both. While the bike we rode had stock internal dimensions, some window shopping shows that 76mm pistons (up 2mm from stock) are readily available for 1052cc, as is a 4mm stroker crank (62mm compared to the stock 58mm) for 1066cc. You just know that Graves has put it all together for a whopping 1125cc (or even more) at one time or another.

Elsewhere inside the engine, a plethora of Graves' own parts are used, including the cams, valve springs and retainers, and the slipper clutch. Other parts include a YEC (Yamaha Engineering Corporation) close-ratio transmission and ignition, and Carillo rods made to Graves' specifications. Upstream, the team experimented throughout 2003 with the stock 40mm throttle-body assembly, but sometimes reverted back to tried-and-true 41mm flat-slide carburetors, which make more manageable power at smaller throttle openings.

It's that characteristic--manageability--that Graves aimed most for in developing the R1 platform, the idea being that making the bike as easy to ride as possible would pay off more than big horsepower. To that end, the R1's chassis is heavily modified to incorporate a wide range of adjustments allowing the bike to be tailored to the rider, track and conditions. As with the engine, only the bare minimum of stock pieces are retained to meet the rules.

The stock Yamaha frame has its steering head cut off, and a Graves-fabricated piece welded on in its place. This new, bigger tube accepts various cones for the steering-stem bearings that allow the stem to be moved forward or rearward over a 14mm range, and adjustable for rake.

Similarly, Graves carves his own swingarm side plates from billet, incorporating a swingarm pivot that can be adjusted over a 12mm vertical and 8mm horizontal range. The rear end of the stock frame is cut off, and the new plates welded into place. The stock main spars are beefed up with additional sheet aluminum, and the finished frame checked for straightness by Computrack.