New For '99: Dirt
NEW FOR '99: DIRT
TWO-STROKE OR FOUR? REED valves or camshafts? The debate continues as to what type of powerplant offroad riders favor. Here's what's coming on both fronts for 1999.
Heading the four-stroke contingent is Honda's muchanticipated XR600R replacement. Don't expect a Yamaha YZ400F-like motocrosser from the Red Riders, but rather an all-new, full-sized off-road machine. As rumored, it will have an aluminum frame, but not the CR125/250's twin-spar unit. Displacement is unknown, but the engine will be liquidcooled and offer performance comparable to that of the Bajawinning, XR-based factory racers. At presstime, company spokesmen would only confirm that the bike is on its way, and that it will be "really good."
As for the CR125 and CR250 MXers, the key word is re finement. Both bikes sport new fork internals and stiffer springs, revised rear linkages and up dated shock valving. There are equivalent changes to the engines, namely a new top end for the CR250 and transmis sion updates on the CR125. Even with the huge success of its YZ400F, Yamaha isn't resting on its lau rels. The YZ250, for example, has an all-new engine that sits more upright and is positioned lower in the frame. The long-stroke motor benefits from a YZF-type involute-spline transmis sion, more positive triple shift forks, and has a three-valve powervalve as sembly and a powerjet-equipped carburetor.
Chassis changes on both the YZ250 and YZ125 in clude lighter swingarms and shock linkages, plus modified forks with stronger tubes and friction reducing seals. The 125 also has a new cylinder and a power jet carb. As for the YZF Thumper, Yamaha hasn't final ized the `99 model's changes, but expect a slight weight reduc tion. Ditto the enduro-spec WR400F. Kawasaki's forthcoming `99 KX125 and KX250 will have new frames and improved power delivery. Significant effort has also gone into cutting weight. As such, aluminum has been used wherever possible. New, lower top frame rails and thin-wall tub ing have dropped the bikes' cen ters of gravity and helped reduce mass. More compact steering geometry and a shorter swingarm have sliced the 125's overall length by more than an inch. Both bikes get hydraulic/elas tomer bottoming devices in the forks, and external highand low-speed compression ad justers on the shocks. There's also a works-like casting on the shock body (a smart shock?), as seen on the facto ry racebikes.
Engine-wise, throttle-posi tion sensors aid low-end re sponse, while shortened intake runners boost top end. On a fu turistic note, there's a new port cast into the engine cases (transmission sensor, anyone?). The 125 also has a newly designed powervalve and altered cylinder porting. There are no rumors of a four-stroke MXer, but Team Green recently showed a bored and stroked, 400cc KLX300 to its dealers to gauge interest.
As for Suzuki, prototype RMs with inverted forks and revised powervalve assemblies have been spotted local test tracks. No word yet on the rumored, liquidcooled Thumper (CW, June, 1998). Stay tuned.
Jimmy Lewis
