With the introduction of the highly anticipated 2004 Kawasaki KX250F four-stroke, one might assume that the popular KX125 has been neglected in favor of its new-wave brother. After all, who could blame Kawasaki if it had decided to simply slap Bold New Graphics on the two-stroke tiddler and concentrate all of its efforts on the thumper? Not us! With the four-stroke revolution upon us, we could understand if the KX125 was forced to take a back seat to Kawasaki's first entry into the four-stroke motocross market.
Fortunately for KX125 fans, this was hardly the case, as plenty of upgrades and improvements have been made to the winningest 125cc machine of 2003. The new Kawasaki KX125 boasts numerous engine, chassis and suspension revisions that all add up to a significantly better bike for 2004.
Engine-wise, the new KX125 powerplant features reshaped ports and an all-new piston, plus redesigned power-valves that seal better. The exhaust pipe is all new, and is complimented by new dual-stage reeds and a straighter carburetor manifold for better throttle response. The ignition timing is revised to better match the aforementioned changes, and changes have been made to the engine crank for greater durability.
The biggest change made to the bike for 2004, however, is the all-new UNI-TRAK rear suspension system. Unlike previous KX models in which the UNI-TRAK link was anchored to the frame, the link on the new system is anchored on the swingarm. This drastically reduces front-to-back movement of the Kayaba shock as the suspension is compressed. This is said to improve traction under acceleration. Mated to the new suspension linkage is a new Kayaba shock, while a new Kayaba 48mm inverted, semi-sealed cartridge is found up front.
On the track, the changes made to the engine are readily apparent from the first lap. Where last year's KX125 seemed to lack good low-end torque, the new '04 bike has a healthy bottom-end punch. Throttle response is much improved and the bike has a torquey feel that can only be compared to that of the Yamaha YZ125, which has ruled the class for several years now. As the rpms begin to build, the KX125 engine continues to pull strong into a meaty mid-range surge and respectable top-end overrev. Jetting was spot-on, as delivered, as the bike carbureted cleanly throughout the powerband. In stock condition, the '04 pulls just as hard–or harder–than our '03 test bike, which had some mild porting and an aftermarket exhaust. After years of the Kawasaki KX125 being a lackluster turtle in the power department, it's refreshing to see the new generation ('03 and '04) bikes pumping out some serious ponies.
In the handling department, the '04 KX125 still feels like a typical Kawasaki, in spite of the new suspension linkage design. And that's a good thing! We've long admired the KX125 for its nimble, agile feel on the track, and the new bike has all of those same great qualities. The bike goes wherever it is pointed and responds immediately to rider input with little effort. Catching an inside line, sliding through the middle or railing the outside of a tricky corner is no problem on this bike; the KX does it all. The Kawasaki feels well-balanced, though it does feel a little rearward-biased in comparison to some of the other 125s. A few laps, however, is all it takes to become accustomed to the way the bike feels in the air and on the ground.
The new rear suspension tracks superbly under acceleration and keeps the rear wheel on the ground and clawing for traction. Small acceleration chop, G-outs and hard landings are all handled in a predictable, confidence-inspiring manner. The shock is mated perfectly to the revised Kayaba fork, which performs equally well. The front end of the bike is easy to loft over imperfections in the track's surface, but in the event that they are hit head on, bumps, square edges and holes are absorbed masterfully. While both ends are adequately sprung and valved for riders in the 150-165 lb. range, we would recommend heavier springs and a revalve for anyone heavier and/or faster.
For '04, the middle of the seat foam has been raised 8mm, the footpegs have been relocated 3mm higher on the frame and the brake pedal pivot is mounted 11.5mm higher. Though we didn't really expect to feel a difference on the track, the changes did, in fact, open up the rider compartment considerably. So much so, that riding the '03 bike afterwards felt cramped. The best thing about the change in ergonomics is that it helped eliminate our tendency to snag the tops of our boots on the bottom lip of the radiator shrouds.
Braking performance this year is much improved, mostly because Honda's direct front brake line mounting patent has finally expired and the KX lineup now has a shorter front brake hydraulic line. Last year's front brake was powerful, but this year's has even better feel at the lever and requires only one finger actuation. The rear binder is excellent, and not even our drag-happy testers could get it to squeal in protest.
As a package, the 2004 Kawasaki KX125 is a great bike that is much improved over its predecessor. It's obviously lethal in the hands of James Stewart, but the bike as a whole is so easy to ride and go fast on that even riders of “real world” speed can feel like champions in their own right.
On the outside, the 2004 Kawasaki KX125 doesn't look any different than the '03 bike. The second edition of the new-generation KX design, however, is actually much improved, thanks to small refinements that equal a big difference in the way the bike feels on the track. If it had Chevy Trucks bow ties on the shrouds, we could be convinced that this is Bubba's race bike.
Throttle response and low-end pulling power is much improved for 2004, and the Kawasaki KX125 remains one of our favorite tiddlers. Taller, faster, and better handling than the '03, the new KX125 will definitely be in the hunt for best 125 honors in '04. Here, our boy Nate Hawley rips through a Perris Raceway berm.