KX250F Motocross

Just two short years after it was introduced to American motocross racers, the championship-winning KX™250F motorcycle has been revamped – even though it already has five titles under its proverbial belt.

Numerous changes have been made to the potent KX250F. It produces significantly more power than the 2005 model it replaces, and like the new flagship KX450F, the KX250F sports an all-aluminum perimeter frame.

The 249cc, liquid-cooled, four-stroke engine now gives the KX250F a harder-hitting powerband, especially from mid- to high-rpm, and it extends that smooth, traction-grabbing power into the over-rev range.

Additional enhancements include revised intake and exhaust ports, and a revised combustion chamber for stronger low- to mid-rpm performance, while new cam profiles and a higher 13.5:1 compression ratio improve high-rpm performance. To compensate for the increased output, the piston now has a thicker crown.

Other engine modifications include stiffer valve springs to help ensure reliable valve control at high rpm; a surface-hardened crankshaft for additional rigidity; more efficient oil pumps that increase oil flow by nearly 20 percent; a new stick ignition coil that reduces overall weight; and newly designed, high-capacity Denso radiators that deliver superior cooling performance due to their more tightly packed cores and new fin design. Kawasaki also revised the timing and lift of the decompression system, so starting the KX250F is even easier.

The clutch and five-speed transmission have also been modified to include new friction plate material and stiffer clutch springs for improved clutch feel, and the gears have beefier dogs to match the more-powerful engine. Kawasaki engineers have also given the KX250F shift drum a new cam to improve shifting feel.

The most visible change to the KX250F is the aluminum perimeter frame. As with the KX450F, Kawasaki engineers combined their experience designing steel perimeter KX frames and techniques used to construct the Ninja® ZX™-10R sport bike chassis to create an all-new aluminum perimeter frame. Comprised of forged, extruded and cast aluminum parts, the strong but light design gives the KX250F the best possible balance of torsional and longitudinal rigidity necessary for superior handling characteristics.

The frame was designed so that the center of gravity and key chassis dimensions would work together to enhance the rear tire’s ability to drive the KX250F forward instead of squatting under acceleration. Additionally, the four-stroke engine sits in an upright position within the new frame to further aid overall traction.

The slim profile of the KX250F frame, two-piece radiator shrouds that leave the upper frame spars exposed, and careful design of the remaining bodywork make the KX250F feel light and narrow beneath the rider.

The KX250F’s high-performance suspension has been designed to complement the new frame. Up front, a Showa twin-chamber fork keeps the oil and air in separate chambers for consistent damping performance during long motos. On the rear, a new UNI-TRAK® rear suspension system, featuring an alloy swingarm with tapered spars and revised linkage ratios maximizes traction under acceleration.

Front and rear petal disc brakes provide stopping power for the KX250F. This design not only helps to reduce unsprung weight, but the petal shape of the discs helps to clean the brake pads for more efficient braking performance.

In addition to aggressive new bodywork and a new seat, the KX250F comes with a Renthal aluminum handlebar and an aluminum skid plate as standard.

To minimize overall weight, the KX250F utilizes aluminum instead of steel for several components, including the clutch cable elbow, clutch cable fitting nuts, fuel tank fitting nuts, seat mounting brackets, front brake hose clamp and igniter stay bracket. Kawasaki engineers also eliminated the upper mounting brackets of previous designs for the plastic fork protectors.

Optional parts for the KX250F include magneto rotors with different inertias, a 12-tooth countershaft sprocket, top mounting clamp for an oversized handlebar, aluminum and steel rear sprockets, solid petal brake rotors for wet races, different springs for the front fork and rear shock, manual decompression lever and cable, and a 20-inch front wheel.

Those who race their KX250F at designated events are eligible to receive support from Team Green™, Kawasaki’s amateur racing support program. Each year, Team Green provides regional support vehicles and highly trained technicians at more than 100 events, offering technical information and assistance to those who race Kawasaki products. Kawasaki also offers a comprehensive contingency program for amateur and professional riders who place well at designated events.

Engine: Four-stroke single with DOHC and four valves
Displacement: 249cc
Bore x stroke: 77.0 x 53.6mm
Cooling: Liquid
Carburetion: Keihin FCR37 and hot start circuit
Compression ratio: 13.5:1
Ignition: Digital AC-CDI
Transmission: Five-speed with wet multi-disc manual clutch
Final drive: Chain
Frame: Aluminum perimeter
Rake / trail: 27.5 degrees / 4.7 in.
Front suspension / wheel travel: 47mm inverted twin-chamber telescopic fork with 16-way compression and rebound damping / 12.4 in.
Rear suspension / wheel travel: UNI-TRAK® linkage system with 13-way low-speed and 2-turn high-speed compression damping, 17-way rebound damping and fully adjustable spring preload / 12.2 in.
Front tire: 80/100-21 51M
Rear tire: 100/90-19 57M
Front brake: Single semi-floating 250mm disc with dual piston caliper
Rear brake: Single 240mm disc with single-piston caliper
Overall length: TBA
Overall width: TBA
Overall height: TBA
Ground clearance: TBA
Seat height: TBA
Dry weight: TBA
Wheelbase: TBA
Fuel capacity: TBA
Color: Kawasaki Lime Green / Black
* Price and specifications subject to change

Engine
- 249cc, liquid-cooled, four-stroke engine delivers hard-hitting power from mid- to high-rpm
- Wide powerband extends smoothly into the over-rev

Top End
- Revised intake and exhaust ports, and revised combustion chamber improve low- to mid-range performance
- Rev-limiter settings and ignition timing have been revised to extend the engine’s over-rev capability
- New cam profiles help increase high-rpm performance without sacrificing low-end performance
- Piston features a thicker crown to compensate for increased power and higher compression ratio
- Once-piece magneto rotor offers improved reliability
- New stick ignition coil saves weight and offers improved performance

Bottom End
- Crankshaft is surface-hardened for additional rigidity
- Countershaft sprocket has more – and smaller – splines to increase reliability
- More efficient oil pumps increase oil flow by nearly 20 percent

Cooling
- Newly designed, high-capacity Denso radiators are slimmer
- Radiator features more tightly packed cores and a new fin design to deliver superior cooling efficiency

Shifting
- New friction plate material and stiffer clutch springs improve clutch feel
- New clutch lever design compensates for higher spring rate
- Five-speed transmission dogs are beefier to match the engine’s increased power
- Shift drum features new cam for improved shifting feel

Frame
- All-aluminum perimeter frame features composite structure, utilizing forged, extruded and cast components
- The slim profile of the frame, two-piece radiator shrouds that leave the upper frame spars exposed, and careful design of the remaining bodywork make the KX™250F feel light and narrow beneath the rider

Front Suspension
- Showa twin-chamber fork keeps oil and air in separate chambers for stable damping performance during long motos

Rear Suspension
- New UNI-TRAK® rear suspension system features revised linkage ratios to suit the new fame and swingarm
- Alloy swingarm uses cast front section, tapered hydroformed spars and forged chain pullers; the tapered spars are shaped to match the balance of flex and rigidity required of the aluminum frame, and allow additional clearance for the rear brake caliper when the rear suspension is fully compressed
- Smaller rear chain guide reduces overall weight

Brakes
- Front and rear brakes utilize new petal discs, helping to reduce overall weight
- Petal discs help to clean the brake pads for more efficient braking performance

Wheels
- New rear wheel helps to reduce unsprung weight

From the Cockpit
- Renthal aluminum handlebar is strong and reduces overall weight
- Short-length grips feature a special pattern to reduce vibration transmitted from the bars to the rider

New Styling
- New bodywork and new seat have aggressive style

Options
- Different inertia magneto rotors
- 12-tooth countershaft sprocket
- Top handlebar clamp for an oversized bar
- Aluminum and steel rear sprockets with optional tooth sizes
- Solid petal brake rotors for wet racing conditions
- Optional springs for the front fork and rear shock
- Manual decompression lever and cable
- 20-inch front wheel