Kawasaki Kx250 Desert/ Enduro
KAWASAKI KX250 DESERT/ ENDURO
As good as a factory model
OBJECTIVE: CHANGE A 1987 KAWASAKI KX250 MOTOcross machine into an off-road bike for trail riding in the mountains and desert, and for use in an occasional enduro. After a few not-so-radical engine and chassis modifications, our transformed KX250 became an excellent enduro machine and a blast to ride in just about any off-road situation. We enhanced the long-stroke engine’s inherently good low-end pulling power by switching to an ignition system from a 250 Tecate Four ATV. Not only does that $386 system have a flywheel that’s a pound heavier for smoother, more-controllable low-rpm power, but it also has a 35-watt lighting coil to power a headlight and taillight. We hand-made a plastic spacer that allowed us to use the stock KX ignition cover.
To increase the mid-range and top-end power without losing low-end (not an easy trick), we installed a Roost Boost ($52.95) from Answer Products ([818] 257-4411 ), a little electronic black box that modifies the stock ignitionadvance curve. That single change gave the engine a more powerful and responsive mid-range that easily flies the front wheel to clear rocks or logs in the trail. And the engine has a rush of top-end power that’s more like what you'd find on a heavily ported 125 motocross bike. With the new ignition curve, however, we chose to lower the compression ratio to eliminate pinging under load by using a stock Kawasaki Tecate head gasket ($7.88).
Since we ended up with an engine that produces enough power over a wide enough rpm range to humble many Open-class bikes, we found no need for a wide-ratio transmission. With the standard MX final gearing, low gear will handle most tight trail conditions; dropping the countershaft sprocket one tooth lets the KX250 deal with deepwoods conditions very comfortably; and installing a onetooth larger countershaft sprocket turns the woods bike into a desert screamer that Open bikes have trouble outrunning. For anyone who does need a wider-ratio gearbox for a KX250, however, Kawasaki offers a four-gear, $ 133 set of cogs that spaces fourth gear farther away from third, and fifth farther from fourth.
Turning to the chassis, we tried two different ways to improve the fork action. First we installed an $87.65 damper kit from Terrycable ([619] 244-9351 ), along with new fork springs ($49.95) from Progressive Suspension ([619] 948-4012). With 10-weight suspension fluid set at a level of 6.5 inches from the tops of the tubes, this combination worked well. Fork action was smooth, comfortable and controllable on most types of enduro terrain.
We also tried a Kawasaki KYB cartridge-type fork kit that raises front-fork performance a notch higher than any conventional damper can match. At $300, this is an expensive modification, but worth the price for a serious rider. There is less front-end dive, and the fork imparts a solid, confidence-inspiring feel that a conventional fork can't match. This added degree of confidence invariably results in faster speeds through nasty sections of trail.
Getting the rear suspension to behave in a like manner wasn’t easy, but we succeeded. We had Works Performance ([818] 710-1010) do what it calls a “Heart Transplant” on the rear shock by installing new damping valves, refilling the unit with good damping fluid and recharging with nitrogen, all for $ 129.95. That’s cheaper than replacing the entire shock, and undoubtedly works better, as well. The rear suspension now is very compliant on square-edged obstacles, and it provides incredible control when skipping across sand whoops, blasting down highspeed trails and landing from killer jumps. And the bike always is stable and precise, on rough ground as well as smooth, and whether going straight or carving through corners.
To get adequate fuel capacity, we installed a 3.5-gallon gas tank ($150 from IMS at [714] 781-5849]. The tank holds an adequate supply of gasoline for long loops, yet its slim shape lets the rider easily slide forward for tight turns. We also fitted a KDX200 headlight/numberplate ($63.59) for enduro use, and added Acerbis handguards ($24 at motorcycle dealers) to protect the rider’s hands. To protect the low-hanging parts of the KX’s exhaust pipe, we bolted up a pipe guard ($32.65) from Malcolm Smith ([714] 687-1300). The pipe also needed a spark arrester, of course, so we chose the $39.95, slip-on Sparky ([714] 779-5318) unit because it is so inexpensive and easy to install. While we were at Malcolm Smith’s outlet, we also picked up an MS Products O-ring chain for the KX, a $46.95 replacement for the short-lived stock chain.
While testing this KX250 project enduro bike, we had a chance to run it head-to-head against an ’87 KTM 250 and an ’87 Husky 250; and that comparison confirmed our success with the Kawasaki, for everyone felt that the KX was just as good as those specialized enduro bikes at most things, and maybe a bit better at others. On top of that, the majority of the riders who tested all four of the project bikes detailed here picked the KX as the best one of the bunch for riding in a variety of terrain. Some of them thought the Kawasaki would be hard to beat in the desert; but a couple of them felt the KX enduro would just be hard to beat, period.
