After an ultra-successful Supercross campaign which saw Jake Weimer and Christophe Pourcel both capture championships aboard this year’s Kawasaki KX250F (learn more about this machine in the 2010 Kawasaki KX250F First Ride) Team Green is at it again releasing a moderately updated KX250F for 2011.
The big change in the motor department is the fitment of a simple and lightweight fuel-injection system. The setup is similar to the one employed on the 2009-and-up KX450F. A slew of componentry replaces the mechanics of a carburetor including an electronic control unit, 43mm diameter throttle body, aluminum fuel pump and a single injector which no doubt adds a small amount of weight. Fuel capacity is also down 0.2-gallons.
The system is powered without a battery by the electricity generated by the rotation of the crankshaft. Sufficient power is generated by the initial movement of the kickstart lever so the bike can be started with one kick.
Next to never having to worry about the bike bogging or hesitating during acceleration is the extreme engine tune-ability offered by Kawi’s system. With the optional Kawasaki Fuel Injection Calibration Kit the rider can alter engine fuel and ignition maps with their PC-compatible computer. Furthermore it also features a data logging feature. We tested it last year with fantastic results. Make sure to read the report for all the details.
Another important update is the piston, which has a reshaped surface and slides within a slightly shorter cylinder. This boosts compression to 13.5:1 (up 0.3). Additionally the intake camshaft allows for more valve lift. Stronger valve springs have been fitted to cope with the new design. Lastly, the crankshaft balance has been altered to complement the changes.
The engine sucks in air from a slightly larger air intake boot while exhaust gas is pumped out from a longer head pipe and a quieter muffler which is said to comply with the AMA’s 94 dB sound limit without compromising peak power production.
The spark plug is now longer and powered by an updated coil said to create a hotter spark. The shifting mechanism and second and fourth gear transmission ratios were modified and a 50-tooth rear sprocket was fitted to complement the engine changes.
The left fork leg provides compression and rebound damping while the right leg handles spring preload adjustment.
After an extensive chassis overhaul in ’09 (find out all the details in the 2009 Kawasaki KX250F First Ride), followed by subtle rigidity tweaks this year to the twin-spar aluminum frame and swingarm, there are no frame or swingarm changes for ‘11. What has been updated is the suspension with the inclusion of an innovative Showa Separate Function Fork.
As opposed to a conventional motocross fork, the new piece separates the spring and damping circuits between each leg. The right leg now accommodates the main spring and adds spring tension adjustability via a blue adjuster atop the fork cap – just like on a modern Superbike. The left leg handles damping with a conventional cartridge damper assembly inside. Compression and rebound damping can still be adjusted via a clicker atop the fork cap and at the bottom of the leg. One of the main benefits of this fork is a claimed 25% less stiction, less weight and easier adjustment.
The fork now sits in new triple clamps with a 1.0mm offset reduction to 22.5mm with the aim of making it steer even easier. The Showa gas-charged shock absorber has new damping settings to complement the massive fork upgrade and moves through the same linkage. It still offers four-way adjustability in the form of spring preload, high/low-speed compression and rebound damping. Other changes include a more grippy material used on the seat and a more durable chain guide.
All said and done the ’11 KX250F weights a little more than a pound over its predecessor. Price hasn’t yet been announced but expect it to be above $7000. The bike will arrive into US dealerships beginning in July, but you can expect a full Motorcycle USA test toward the end of June.