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Both members of the Extreme Lean Motorsports racing team ride 1993 Yamaha TZ250's. The TZ250 is a machine designed solely for road racing. A four-wheeled equivalent would be a Formula 1 or Indy car. The motor is a two-stroke, liquid cooled, 90-degree V-twin, with cylinders pointed 45 degrees up and down from horizontal. The lower cylinder's carburetor is in the middle of the V, the top behind the cylinder. A counter-balancer is included. Many motor parts from later models will bolt on (cylinders, head, ignition, stator and pipes), allowing you to get current-model power without having to buy a completely new bike. The gearbox is cassette-style; you can pull the gear cluster out with the motor in the frame. Gear changes can be done in something on the order of an hour (or less if you are in a hurry and know what you are doing). The frame is a twin-spar aluminum fabrication with cast steering-head and swingarm-pivot sections. The swing-arm is curved up on the right side to allow the lower exhaust pipe to tuck in close with adequate ground clearance. The lower carb is fed from a duct on the right-side, leading edge of the lower fairing. The top carb was fed via a NACA duct on the left side of the fairing leading into a scoop feeding air into the airbox. Later models of the TZ250 had slightly different arrangements for feeding air to each of the carbs. |
In most club-level Formula Two classes, the 250 GP machines run with the 600cc four-strokes. Even with the much smaller engine capacity, the 250 GP machines rule the F-2 class. A modern 250 makes about 85 hp, while a 600 makes about 100hp in stock trim. Most of the 600s have been tuned to some degree, but a fair number of them also attempt to run in the Modified Production or Superstock classes, limiting the full development potential. The difference is that the 250 weighs about 220 pounds and the 600s all start over 400 pounds. The 600 could be trimmed down to below 350 fairly easily, but it starts to get expensive after that. Suffice it to say that the good power and aerodynamics combine with the incredible cornering and braking ability to make an incredibly fast race machine. In the unlimited F-1 races at Willow Springs, a TZ250 often nabs a podium finish, and several times the win, at a track that is high-speed and horsepower hungry. The 250s are a joy to ride because of their incredible handling as well as having enough power to give incredible acceleration. Riding is effortless because of their quick steering and unflappable stability. If you ever think you have gone in to a corner too fast, just turn it in and the bike rails around the corner. The bike's limits are so high that you need to completely change your view of how to ride and react. Getting anywhere near the maximum potential out of this bike takes a lot of work. |
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