THUMPER RACING KLX 340 TEST–JULY 8
With all of the hi-performance four-strokes scorching the tracks and trails, you?d think that the Kawasaki KLX300 would go the way of the dinosaurs, but you?d be wrong. Hop-up shops are doing more KLXs now than ever before, and the comparatively inexpensive Kawasaki has a lot of things going for it. The first water-cooled Japanese thumper to hit our shores, the KLX has modern suspension and a perimeter frame that?s great for smaller riders. Back when the KLX was first introduced, Gary Hazel was working at Team Green, so he knows the machine inside and out. Those first 250s were hard to start and had cam-chain problems. Kawasaki fixed weak points and punched displacement to 300cc for the 1997 model year. Now in its eighth year, the KLX has gained a following like the XR250R, and the aftermarket knows how to make it rip.
From The July Issue Of Dirt Bike Magazine
Just as the KLX benefitted from a jump from 250cc to 300cc, more displacement equals more bark. Thumper Racing bored the Nikasil cylinder to accept a sleeve and an 84mm piston, bumping displacement to 340cc and dropping compression to 10.5:1 for the kit. Pistons with compression of 11:1 (stock) and even 12:1 were tried (YZFs are 12.5:1), but the intake valves would cup and fail with the added pressures and temperatures. Hazel felt the lower compression and extra torque of the larger piston would give better low-end without having to pour thousands of dollars into the engine.
Hazel tried a few carburetors, including a pumper FCR Keihin, and saw gains, but fitment was a problem, so the stock carb was rejetted for the mods. More for durability than performance, the project 340 also got a Hinson clutch, heavy-duty clutch springs and Thumper serviceable oil filter. Lastly, Hazel felt the KLX was geared too low, especially with the added boost, so he raised overall gearing by going from a 50 to a 47.
Also, the kitted KLX is easy to start and keep running. Lump got first-kick starts every time, while Dick Burleson usually took three to light her up, and we never stalled it on the trail.
FROM MUSH TO PLUSH
ARM FOR NO HARM