The 2011 Kawasaki KX450F and KX250F have been released, with the latter considered Kawasaki’s ‘new’ cross bike. Both bikes are being released as “ready to race” models with new features including digital fuel injection and an optional data logging system called the ECU Setting Tool.

The KX450F has a single cylinder, 449 cm3 liquid-cooled motor and a new fuel system for more torque at lower revs. The Bridge-Boxed bottom piston first introduced on the 2010 model appears again on the new model, with the 450cc designed to be more powerful with better gear transition.

The chassis components remain mostly unchanged since last year, but the KX450F has a new Uni-Trak suspension system for racing riders at the rear, while the front of the bike has a Kayaba AOS fork with separate oil and air functions. The digital fuel injection system includes the small ECU which requires no battery, thus reducing weight.

The KX250F has some significant upgrades for 2011 and is also designed as a race bike with the new fuel injection system producing more power. It has a new chassis upgrade in the form of a Separate Function Fork which divides spring and damping functions. The highlights of the new KX250F are:

2011 Kawasaki KX250F and KX450F

* New Digital Fuel Injection (DFI®) system allows consistent fuel delivery, quick starts and easy adjustability; prevents engine hesitation after landing from jumps
* Optional ECU Setting Tool allows custom tuning and data logging
* New Showa Separate Function Fork (SFF) divides spring and damping functions – ­­ springing in the right leg and damping in left provide less friction, better performance and easier adjustability
* Revised suspension settings front and rear aimed at race-experienced riders
* Increased engine performance via higher compression and exhaust/intake changes
* Super-hard titanium nitride coating on the outside of the inner fork tubes reduces stiction and improves suspension action, while also helping to prevent scratches and tube damage
* High-performance piston featuring bridged-box-bottom design
* Engine tuned to achieve the widest possible torque band, maximizing traction through more of the rev range
* Stainless steel exhaust features longer header section and larger-volume muffler, quieting emissions to 94 dB

For more details including technical specs, on the new KX250F and KX450F from Kawasaki, check out the Kawasaki offroad site. Technical specs of the Kawasaki KX250F are as follows:

Engine

Engine type: Liquid-cooled, 4-stroke Single
Displacement: 249 cm³
Bore x stroke: 77.0 x 53.6 mm
Compression ratio: 13.2:1
Valve/Induction system: DOHC, 4 valves

Fuel system
Carburettor: Keihin FCR-MX37
Ignition: Digital AC-CDI
Starting: Primary kick
Lubrication: Forced lubrication, semi-dry sump

Transmission
Transmission: 5-speed, return
Final Drive: Chain
Primary reduction ratio: 3.350 (67/20)
Gear ratios: 1st: 2.142 (30/14)
Gear ratios: 2nd: 1.769 (23/13)
Gear ratios: 3rd: 1.444 (26/18)
Gear ratios: 4th: 1.200 (24/20)
Gear ratios: 5th: 1.045 (23/22)
Final reduction ratio: 3.692 (48/13)
Clutch: Wet multi-disc, manual

Frame

Frame type: Perimeter, aluminium
Rake/Trail: 27.7°/122.3 mm
Wheel travel, front: 315 mm
Wheel travel, rear: 310 mm
Tyre, front: 80/100-21 51M
Tyre, rear: 100/90-19 57M
Steering angle, left / right: 42° / 42°

Suspension
Suspension, front: 47 mm upside-down twin-chamber telescopic fork
Compression damping: 16-way
Rebound damping: 16-way
Suspension, rear: New Uni-Trak
Compression damping: 13-way (low-speed), 2-turns or more (high-speed)
Rebound damping: 17-way
Spring preload: Fully adjustable

Brakes
Brakes, front: Single semi-floating 250 mm petal disc
Caliper: Dual-piston
Brakes, rear: Single 240 mm petal disc
Caliper: Single-piston

Dimensions
Dimensions (L x W x H): 2170 mm x 820 mm x 1270 mm
Wheelbase: 1470 mm
Ground Clearance: 340 mm
Seat height: 955 mm
Fuel capacity: 8.0 litres
Curb Mass: 105,1 kg

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