KX250F enters the high-revving arena of four-stroke MX bikes
After months of public speculation, Kawasaki Motors Corp., U.S.A., announced it is indeed entering the world of four-stroke motocross with the brand’s first-ever four-stroke motocross bike. The all-new Kawasaki KX250F for 2004 extends Kawasaki’s prestigious history of building championship-winning racing motorcycles, taking its place next to the entire race-winning KX model line.
With an all-new liquid-cooled four-stroke engine, new Kawasaki perimeter frame and suspension, the KX250F is designed for one purpose: victory in 125-class motocross and Supercross competition. “The KX250F is designed to be lighter, faster and better handling than the competition,” said Steve Fischer, off-road motorcycle product manager for Kawasaki. “Just as important, it’s easier to ride, so KX250F racers can look forward to more wins at the track.”
The KX250F is powered by a 249cc, liquid-cooled, four-stroke, single-cylinder engine featuring double overhead cams and four valves. With an over-square bore and stroke of 77.0 x 53.6mm to help ensure high revs, it features a forged piston, chrome composite plated aluminum cylinder, titanium valves, billet camshafts and alloy steel tappets.
The engine’s “semi-dry” oil sump contributes to a low center of gravity. Oil is routed internally through the cylinder’s bolt passageways, eliminating the weight and complexity of external oil lines and increasing the engine’s durability.
To help keep the KX250F as light as possible, several engine components are made from lightweight materials, including magnesium generator, outer clutch and cylinder head covers, titanium exhaust headpipe and aluminum silencer.
The KX250F is designed to start easily, whether hot or cold, due to its Kawasaki Automatic Compression Release (KACR) system and hot start circuit. KACR slightly opens one exhaust valve while the engine is being kick started to ease compression. The Keihin FCR37 flat-slide carburetor, which is operated by a push-pull throttle, is also equipped with hotstart circuit. If the KX250F is tipped over or stalled, the rider pulls a small lever that is unitized with the clutch lever, drawing extra air into the carburetor to give it a leaner, faster-burning fuel mixture, making starting easier.
Ignition is provided by a digital AC-CDI system featuring a dual ignition map and rev limiter. When the transmission is in neutral, the ignition allows for a low idling speed. When the transmission is in gear, the second ignition map is used, increasing idle rpm for reduced engine-braking effect.
The new engine is matched to a quick-shifting, five-speed transmission. The transmission uses a ratchet shift mechanism for light shifting action, and clutch components are the same as those used on the KX125.
The KX250F frame has new D-section tubes on the upper frame rails, enabling the slim bodywork to “hug” the frame more tightly. Plus, frame width has been narrowed 40mm at the footpegs. Combined with a steeper rake angle and foot pegs that are placed higher and closer together in the frame, the slimmer profile improves rider position on the bike for enhanced cornering performance.
A new Kayaba semi-sealed, 48mm inverted cartridge fork with 11.8 inches of travel handles front suspension duties for the KX250F and features 16-way compression and rebound damping settings. On the rear, a revamped UNI-TRAK® rear suspension provides 12.2 inches of travel with 16-way compression and rebound damping settings.
Unlike previous KX models in which the UNI-TRAK link was anchored to the frame, the link on the new system is anchored on the swingarm. This drastically reduces front-to-back movement of the Kayaba shock as the suspension is compressed, resulting in smoother suspension action and significantly improved traction, especially while accelerating.
Stopping power is provided by a dual-piston 250mm front disc brake. The brake hose is made of a single layer of Kevlar and is routed directly to the front caliper, improving brake feel and reducing weight. The 240mm rear brake features a more compact caliper to ensure adequate clearance for the muffler when the suspension is fully compressed, and the brake pedal is forged for high strength and light weight. The KX250F is fitted with lightweight wheels and mounted with 80/100-21 Bridgestone M51 front and 100/90-19 M57 rear tires. A 20-inch front wheel is also available as an option through Kawasaki dealers.
Restyled bodywork distinguishes the KX250F from its two-stroke cousins, including a longer rear fender, side covers that are more oblong in shape and sharply angled radiator shrouds that give the bike an aggressive, “streamlined” stance. Plus, the seat is flatter than on previous KX models and features a textured slip-resistant cover. In addition to redesigned fork guards, the KX250F also features an aluminum skid plate and plastic side guards to protect the engine.
Because the KX250F engine is more fuel efficient, the fuel tank has a 2.0-gallon capacity, providing additional weight savings.
Like all KX motorcycles, the new KX250F comes with the support of Team Green„¢, Kawasaki’s amateur support program. Team Green’s regional support vehicles and highly trained technicians provide technical information and assistance for anyone who rides or races a Kawasaki. Team Green also offers a comprehensive contingency program for amateur and professional riders who place well at designated events.
Information about the new KX250F motorcycle and Kawasaki’s complete line of family recreational products can be found on the Internet at www.kawasaki.com. Accessories for KX motocross bikes can also be purchased online at www.buykawasaki.com.
Kawasaki Motors Corp., U.S.A., (KMC) markets and sells at wholesale Kawasaki motorcycles, ATVs, JET SKI® watercraft, MULE„¢ utility vehicles, power products and small engines. Kawasaki’s tagline, Let the good times roll„¢, is recognized worldwide for the spirit of fun, adventure and high performance that characterizes the Kawasaki recreational vehicle line. Kawasaki product lines are sold through a network of more than 1,500 independent retailers. The company and its affiliates employ nearly 2,400 people in the United States, with approximately 550 of them located at the Irvine, California headquarters.
Features and Benefits:
- Liquid-cooled, four-stroke single cylinder engine was designed using the latest technology, resulting in a lightweight, compact and powerful engine that produces usable torque throughout the entire rpm range
- Automatic centrifugal decompression system to ease starting
- 37mm Keihin FCR flat-slide carburetor equipped with TPS, and the accelerator pump contributes to quick throttle response
- Over-square bore and stroke of 77.0 x 53.6mm helps ensure high reliability at high rpm
- Thin-wall cylinder head contributes to lightweight, compact design
- Chrome composite plated aluminum cylinder is extremely short to prevent over-cooling of crankcase and subsequent power loss
- Forged, two-ring piston is tin-plated to reduce wear and the piston skirts have fine grooves to help ensure oil retention and low friction
- Billet cam profiles are designed for wide powerband and high peak power
- Two-stage ignition system provides low idle speed when transmission is in neutral; when in gear, it increases idle rpm for reduced engine braking
- Semi-dry sump design keeps oil away from the crankshaft to reduce pumping loss and contributes to a lower center of gravity
- Reed valve located between the crankcase and transmission case reduces pumping loss and prevents oil from re-entering crank chamber
- Oil feed to top end is internal, via bolt passageways, eliminating the weight and complexity of external oil lines and increasing reliability
- One-piece water pump/oil filter cover saves weight and adds to compactness
- Lightweight 3-way (Y-shaped) molded cooling hose eliminates need for junction and clamps
- Titanium valves and headpipes, magnesium generator, outer clutch and cylinder head covers reduce overall weight
- Five-speed uses ratchet system for light shifting action
- Clutch utilizes the same dependable components as found on the KX125
- Kawasaki perimeter frame borrows proven technology from race-winning KX125 and KX250
- New D-section upper tubing allows bodywork to “hug” the frame more tightly—the slimmer profile improves rider position for enhanced cornering
- Adjustable rubber handlebar mounts help reduce vibration
- Steep rake angle enhances cornering performance
- Footpegs are located higher and more closely together, allowing more bank angle when turning
- New Kayaba semi-sealed, 48mm inverted cartridge fork features check valves to control internal pressure, resulting in precise damping and better fork action throughout the stroke
- New UNI-TRAK® rear suspension link is anchored on the swingarm, drastically reducing front-to-back movement of the shock, resulting in smoother, more stable action and improving traction at the rear wheel when accelerating
- Rear shock features a bleeder bolt to facilitate oil changes
- Because the link anchors on the swingarm rather than the frame, engineers were able to construct a lighter frame
- Front and rear rims feature an extremely light design
- Front spokes are stepped both at the nipple and at the hub for lighter weight
- Dual-piston front disc brake system uses Kevlar hose routed directly to the front caliper, producing strong brake performance
- Lightweight rear brake system uses a lighter, compact caliper to ensure adequate clearance for the muffler when the suspension is fully compressed
- Brake pedal is forged for high strength and light weight
- Restyled tank, seat, rear fender, side covers and radiator shrouds give it sharp, aggressive stance
- Right side cover has heat shielding to deal with higher temperatures from the large silencer
- Fuel tank capacity is 2.0 gallons; the more fuel-efficient four-stroke engine gives the KX250F an increased riding range
Kawasaki Options (Available Through Kawasaki Dealers)
- Aluminum and steel sprockets
- Carburetor setting parts
- Front fork and rear shock springs
- Flywheel rotors allow riders to alter the amount of engine inertia to suit riding style and track conditions
- Right handlebar-mounted lever allows manual operation of engine decompression, making it easier to clear a flooded engine
- 20-inch front wheel
2004 KX250F SPECIFICATIONS*
||Four-stroke single cylinder with DOHC, four valves
||Bore x stroke
||77.0 x 53.6
||Keihin FCR37 with hot start circuit
||Five-speed with wet multi-disc manual clutch
||Perimeter style, high-tensile steel with Dsection upper frame rails
||Suspension type, front
||48mm inverted, cartridge-type telescopic fork
||Suspension adjustments, front
||16-way compression and rebound damping
||Suspension type, rear
||UNI-TRAK® single shock system
||Suspension adjustments, rear
||16-way compression and rebound damping, spring preload
||Wheel travel, front
||Wheel travel, rear
||Brakes, front / rear
||Single semi-floating 250mm disc, dualpiston / single 240mm disc, single-piston
||Kawasaki Lime Green
*Specifications subject to change
*Specifications subject to change
*Specifications subject to change