Just two short years after it was introduced to American motocross racers, the championship-winning KXâ„¢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.
Kawasaki KX250F Specifications
- 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: Multi-map digital CDI with K-TRIC throttle position sensor
- Transmission: Five-speed with wet multi-disc manual clutch
- Final drive: Chain
- Frame: Aluminum perimeter
- Rake / trail: 27.7 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 petal disc with dual piston caliper
- Rear brake: Single 240mm petal disc with single-piston caliper
- Overall length: 85.0 in.
- Overall width: 32.3 in.
- Overall height: 50.0 in.
- Wheelbase: 57.8 in.
- Ground clearance: 13.8 in.
- Seat height: 37.6 in.
- Dry weight: 204 lbs.
- Fuel capacity: 1.9 gal.
- Color: Lime Green / Black
- MSRP: $5,999
- 249cc, liquid-cooled, four-stroke engine delivers hard-hitting power from mid- to high-rpm
- Wider powerband extends low-rpm torque and increases over-rev
- New longer, straighter airbox funnel contributes to increased low-rpm response
- Revised carb tuning to suit the engine’s modifications
- New hand polished intake ports. This extremely-smooth surface improves intake flow at every rpm
- Ultra-light thin-stem titanium valves are strengthened by thicker skirts and held by longer guides for increased durability
- Special valve seat material helps prevent wear on the titanium valves
- K-TRIC digital microcomputer controlled ignition system with coil on plug “stick” ignition to save weight and improve performance
- Revised ignition timing improves top-end and over-rev
- Revised piston crown contributes to improved power at high-rpm
- New, looser-fitting piston ring with reduced tension for lower friction
- Crankshaft is surface-hardened for maximum rigidity
- Twin oil pumps ensure proper lubrication and oil scavenging for optimum performance
- Lightweight magnesium clutch, generator and cylinder head covers
- New 20mm taller right-side radiator offers increased cooling capacity
- High-capacity Denso radiators are designed to offer superior cooling in a slim profile
- Radiator features more tightly packed cores and a special fin design to deliver superior cooling efficiency
- An all-new 5-speed transmission with thicker gears offers improved shifting and increased durability
- New shift drum with modifications to the ratchet mechanism for more positive shifting
- New ball bearing shift shaft improves shifter feel
- New stiffer clutch springs (up roughly 20%) give a more direct feel at the lever
- Teflon lined clutch cable provides smooth action and clutch feel
- Five-speed transmission dogs are beefier to match the engine’s increased power
- Shift drum features new cam for improved shifting feel
- All-aluminum perimeter frame features composite structure, utilizing forged, extruded and cast components
- Revised frame stiffness works with new front fork tuning for lighter steering and quicker response both on the ground and in the air
- 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
- New works-style aluminum skid plate for added protection
- New sub springs and revised valving for the Showa twin-chamber fork offer a more progressive response and increased bottoming resistance for lighter, quicker handling and superior suspension action
- Showa twin-chamber fork keeps oil and air in separate chambers for stable damping performance during long motos
- New shock spring and revised valving for improved suspension action
- A new rear shock damping adjustment needle allows more precise tuning of the rear suspension
- 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
- New “sprocket-style” chain roller helps smooth engine braking by reducing drive lash
- Revised front brake master cylinder hose joint allows more lever position adjustment
- Front and rear brakes utilize petal discs, helping to reduce overall weight
- Petal discs help to clean the brake pads for more efficient braking performance
- Stronger rear rim is laced to a rib-less rear hub with new spoke design that helps reduce unsprung weight
From the Cockpit
- Renthal aluminum handlebar is ultra-strong and reduces overall weight
- Short-length grips feature a special pattern to reduce vibration transmitted from the bars to the rider
- Particular attention was paid to the body work underneath the seat to improve the rider‘s grip on the chassis when standing
- New graphics and seat cover have aggressive style that emulates Kawasaki’s race bikes
- Number plates now feature graphical highlights for a bolder appearance
- New colored surface treatment on wheel hubs and engine covers
- 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