2011 Kawasaki KX250F and KX450F Motocross Bikes - First Look

KX250F gets fuel injection and updated chassis, KX450F fine-tuned.

It should come as no surprise that Kawasaki joins Lites-class rivals Honda, Suzuki and KTM by adding fuel injection to its 2011 KX250F. After securing both the 2010 AMA East- and West-coast Lites Supercross titles with riders Christophe Pourcel and Jake Weimer at the helm of Monster Energy/Pro Circuit/Kawasaki-backed KXs, you would think that the Green machines were good enough. But staying at the top is hard business.

Starting with the headline-grabber: Kawasaki's Digital Fuel Injection system features the same 43mm, single-injector throttlebody and lightweight aluminum fuel pump as its big brother, the KX450F. Like on the 450, the system does not require a battery; the engine can be started within three rotations of the crankshaft using the energy generated by the initial kick to power the system. An optional ECU Setting Tool allows owners to select from several ECU maps or to be able to fine-tune a custom map for fuel and ignition to suit different conditions and rider preference.

Compression has been bumped up from 13.2 to 13.5:1 via a modified cylinder and changes to the Bridged-Box Bottom piston. A new intake camshaft provides more lift. Air-cleaner duct volume has been increased, while a longer exhaust header pipe helps produce more low-end and midrange power. A new exhaust silencer has more volume for reduced noise.

Engine changes aren't the only area where Kawasaki concentrated its efforts. The chassis receives significant updates, too. A new Separate Function Fork (SFF) differs from a conventional unit by separating the spring and damping tasks. The right leg contains the spring (the preload adjuster is atop the blue anodized cap), while the left leg incorporates the cartridge assembly and fork oil to manage compression and rebound damping. Additionally, the fork sliders feature a titanium-oxide coating which, combined with the rest of the new design, is said to reduce stiction and improve performance. The shock was revised to suit the new setup at the front.

An updated transmission, new bodywork and gripper seat round out the highlights.

#### SPECIFICATIONS: KX250F
Engine:|Four-stroke single with DOHC and four valves
Displacement:|249cc
Bore & stroke:|77.0 x 53.6mm
Compression ratio:|13.5:1
Fuel injection:|43mm Keihin throttle body
Ignition:|Digital CDI
Transmission:|Five-speed with wet multi-disc manual clutch
Rake/trail:|28.2º/4.7 in.
Front suspension/wheel travel:|47mm inverted Showa SFF telescopic fork with spring preload adjustability and 22 position compression and 20 position rebound damping adjustability/12.4 in.
Rear suspension/wheel travel:|Uni-Trak® linkage system and Showa shock with 19 position low-speed and stepless high-speed compression damping, 22 position rebound damping and fully adjustable spring preload/12.2 in.
Front tire:|80/100-21
Rear tire:|100/90-19
Front brake:|Single semi-floating 250mm petal disc with dual piston caliper
Rear brake:|Single 240mm petal disc with single-piston caliper
Overall length:|85.4 in.
Overall width:|32.3 in.
Overall height:|50.0 in.
Wheelbase:|58.1 in.
Ground clearance:|13.0 in.
Seat height:|37.2 in.
Curb weight:|232.7 lbs.
Fuel capacity:|1.9 gal.
Color:|Lime Green
MSRP:|N/A
#### SPECIFICATIONS: KX450F
Already one of the most potent MXers on the market, the KX450F has received a number of improvements. Among them are a new piston, a higher-volume and quieter muffler and a revised ECU with hotter and longer-duration spark for better low-end response. Upgraded engine mounts optimize chassis flex, while changes to the fork and shock improve damping characteristics.
Engine:|Liquid-cooled, four-stroke single with DOHC and four-valve cylinder head
Displacement:|449cc
Bore & stroke:|96.0 x 62.1mm
Compression ratio:|12.5:1
Fuel injection:|43mm Keihin throttle body
Ignition:|Digital DC-CDI
Transmission:|Five-speed
Rake/trail:|26.7º/4.6 in.
Front suspension/wheel travel:|48mm inverted, Kayaba AOS with DLC coated sliders, 22-position compression and 20-position rebound dampening adjustment/12.4 in.
Rear suspension/wheel travel:|Uni-Trak® linkage system and Kayaba shock with 50mm piston, 22-position low-speed and stepless high-speed compression dampening, 33-position rebound dampening and fully adjustable spring preload/12.4 in.
Front tire:|90/100-21
Rear tire:|120/80-19
Front brake:|Single semi-floating 250mm petal disc with dual piston caliper
Rear brake:|Single 240mm petal disc with single-piston caliper
Overall length:|86.0 in.
Overall width:|32.3 in.
Overall height:|50.4 in.
Wheelbase:|58.3 in.
Ground clearance:|13.2 in.
Seat height:|37.8 in.
Curb weight:|N/A
Fuel capacity:|1.9 gal.
Color:|Lime Green
MSRP:|N/A

2011 Kawasaki KX450F fork

2011 Kawasaki KX450F

2011 Kawasaki KX450F

ECU tool

2011 Kawasaki KX250F Fork

2011 Kawasaki KX250F Bridged-box bottom piston

2011 Kawasaki KX250 cylinder

2011 Kawasaki KX250F throttle body

2011 Kawasaki KX250F fork caps

2011 Kawasaki KX250F shock

2011 Kawasaki KX250F throttle body

2011 Kawasaki KX250F engine

2011 Kawasaki KX250F

2011 Kawasaki KX250F

2011 Kawasaki KX250F

2011 Kawasaki KX250F