2013 Kawasaki KX450F & KX250F First Look

May 23, 2012
Bart Madson
By Bart Madson
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Bashing away at the MotoUSA keyboard for nine years now, Madson lends his scribbling and editorial input on everything from bike reviews to industry analysis and motorcycle racing reports.

Kawasaki has revealed a 2013 motocross lineup with significant upgrades. Team Green kept busy in the off-season, debuting a new pressurized air fork on its KX450F, while the KX250F also gets revisions for the 2013 model year.

2013 Kawasaki KX450F

2013 KX450F
The 2013 Kawasaki KX450F makes use of an all-new Pneumatic Spring Fork (PSF) design from KYB.

Kawasaki gave its 2012 450 MX thumper a serious redesign, but that didn’t stop the engineers from making some changes one year out. The big news is the Pneumatic Spring Fork (PSF) from KYB. The PSF design replaces traditional coil springs with pressurized air. The pneumatic system promises to reduce friction and oil contamination compared to the conventional setup, provides better bottoming resistance, and it shaves weight by 1.7 pounds. The new fork can be tuned via hand pump, and Kawasaki also claims the PSF “improves smoothness and enhances the fork’s ability to follow terrain contours.” The KX450F also sources a new swingarm with improved rigidity.

The big KX benefits from some engine tuning tweaks for, of course, more power. Kawi PR also states a revised piston crown and less lift from the intake cam improve bottom-end power. There have also been refinements to the braking system, with a new master cylinder and 240mm rear rotor. The KX still sports the adjustable ignition mapping and Launch Control from the 2012 model. Expect more explanation of the KX features, including the all-new air fork system, after a future testing opportunity.

2013 Kawasaki KX250F

2013 KX250F
The 2013 Kawasaki KX250F gets modest engine mods, upgraded fork and tweaks to its chassis and ergonomics.

The KX250F enters 2013 with some engine mods, revised fork and chassis/ergonomic tweaks. First to introduce EFI in the 250 class, the little Kwakker benefits from the plug-and-play adjustable ECU and ignition mapping found on its big brother. The 250 engine features claims of improved top end courtesy of new cam timing, wider intake ports and revised intake for more direct airflow. Team Green also shortened 0.1mm from the cylinder to bump compression. The KX250 also sports a new stainless steel exhaust, with shorter header and resonator chamber claiming to boost bottom-end power and cut down on noise. The muffler is also shorter, but with a larger cross section.

Kawasaki PR touts upgrades to the 250’s Separate Function Fork (SFF), with claims of “improved rigidity and less stiction.” Built by Showa, the SFF design divvies out spring and damping duties to the separate fork legs. Out back the Showa shock offers revised damping settings, with separate adjustments for high and low-speed damping.

The frame this year is 4mm narrower across main spars, and tweaks to the chassis (steering head gusseting, rear shock mount and left rear engine hanger bracket) are promised to “slightly reduce rigidity for lighter handling and increased rear wheel traction.” The ergos get slimmer, too, with the radiator shrouds trimmed and a fatter seat/tank interface – all of which provide for better movement and the ability to sit farther forward on the bike. Longer grips, also sourced on the 450, allow riders the ability to move their hands in further.

Expect a full report on the updated KX250F after MotoUSA attends the press launch early next month.