Yamaha Yz250 Off-Road Racer
YAMAHA YZ250 OFF-ROAD RACER
A jack-of-all-trades
OBJECTIVE: BUILD A COMPETITIVE OFF-ROAD RACER that can win hare scrambles, Grand Prix and desert races, while still being a good all-around playbike.
Yamaha’s latest YZ250 has a really nice engine, one with a wide powerband that starts pulling at a low engine speed, continues building power through a healthy mid-range, and then extends into a good top-end. That’s excellent for this bike’s intended use, so we left the engine and pipe stock except for a switch to Boyesen reeds (about $29.95 at local motorcycle dealers) to sharpen throttle response. Otherwise, the YZ250 engine needed no major changes to be competitive and reliable.
We saw no reason to mess with the gearbox ratios, either; a close-ratio transmission is perfect for off-road racing in the West. For competing in a high-speed Grand Prix or desert event, we replace the countershaft sprocket with a one-tooth larger sprocket.
A $ 150, 3.5-gallon gas tank from IMS ([714] 781-5849) replaces the standard MX tank for these same events, giving the required 100-mile range. It fits perfectly and lets the rider move forward easily.
Our YZ250 has excellent suspension, thanks to an $87.65 damper kit from Terrycable ([619] 244-935 1 ). We also cut four coils from the stock springs to increase their rate, and made PVC plastic spacers that preload each spring 2mm. Those modifications have turned a terrible fork into one that soaks up the small hits comfortably, never hydraulic-locks, and seldom bottoms off big jumps.
Race Tech ([714] 594-7755) revalved the YZ shock and cut the stock spring. This cost $185, but turned a poor shock into an excellent one. Rear-end hop going into a bumpy downhill corner—a major problem with the stock shock—has been eliminated. The YZ also now lands smoothly from killer jumps.
This vast improvement in suspension lets a rider appreciate the YZ’s inherent handling capabilities. It will easily turn under other bikes in a tight, bumpy corner, and it goes where the rider wants it to go when railing through a berm. Straight-line stability is excellent down choppy, torn-up straights, and the overall handling in sand is precise and confidence-inspiring.
Personal touches to the YZ250 include a $29.95 Yamaha OW-style low handlebar from Answer Products ([805] 257-441 1), Honda CR grips (about $9 from Honda dealers), a Dunlop K-190 front tire, a Bridgestone M-22 rear tire, and Acerbis handguards with extenders. We add a $39.95 Sparky ([714] 779-5318) when the rules require a spark arrester; and we have installed an O-ring chain ($46.95), a stronger chain guide ($39.95) and a pipe protector ($32.65), all from Malcolm Smith ([714] 6871300).
The finished product is a fun, reliable off-road YZ250 that can be raced in many types of competition, yet it is an extremely nice playbike. We like it—a lot.
