Light and Faster 250cc Motocrosser
The KX design philosophy – to put midlevel to expert riders on the top step of the podium – has not changed since the brand was launched over 40 years ago. The KX250F has a history of winning: in the extremely competitive 4-stroke 250cc class it is the racer with the most AMA Supercross and Motocross titles. Adding to its highly acclaimed engine and chassis performance, numerous industry firsts and advanced technology, the 2018 model offers a more powerful engine, a light chassis, and matched with the slim ergonomics, making the new model the fastest KX250F yet.
Key Features of the 2018 KX250F
- 4 position adjustable handlebar
- Separate Function front Fork (SFF) Type 2 with revised settings
- Oversized petal disc brakes
- Factory styling – graphics and finishes
- 2 position adjustable footpegs
- Uni-Trak rear suspension with revised settings
- Next-level Power, Torque and Performance
- Shorter Downdraft-style intake system
- 249cm³ liquid cooled, 4-stroke single with revised dual injectors
- Larger diameter and reshaped longer length exhaust header pipe to help improve bottom-end and mid-range power
- Setting adjustable motocross ECU
- Slim and light aluminium perimeter frame
- The KX design philosophy – to put mid-level to expert riders in the top step of the podium – has not changed since the brand was launched over 40 years ago. The KX250F is perhaps the motocross bike to put you out the front of the pack and keep you there.
Advanced Suspension Technology
Separate Function Front Fork (SFF) Type 2
The KX250F was the first mass-production motocrosser to feature Showa’s Separate Function front Fork (SFF), which separates damping and shock absorption duties:
- Left fork tube: damping assembly
- Right fork tube: spring
The configuration offers both smooth action and firm damping performance – a combination difficult to achieve with a conventional fork.
- Using large φ48 mm inner tubes contributes to greater fork rigidity, resulting in a more planted feel from the front wheel.
- With only one spring, the friction generated between the spring(s) and fork inner tube(s) is greatly reduced (approximately 25% less), resulting in extremely smooth action throughout the fork stroke.
- Being able to use larger damper pistons not only enables smoother action, it also makes firm damping performance possible.
- The large diameter fork tubes enable larger damper components.
Main piston diameter 30 mm
Sub-piston diameter 35 mm
With the larger components, the same damping force as the 47 mm SFF Type 1 can be achieved with a lower internal pressure. With the lower pressure, the 48 mm SFF Type 2 is even better equipped to offer both increased riding comfort and firmer damping performance.
For 2018, the light inner-tube design optimizes fork rigidity. Together with revised shim stack layout and softer spring rate (9.8 N/mm >>9.4 N/mm), the busy pitching effect over braking bumps is reduced, and cornering stability is increased while sharp turn-in is maintained. High-speed stability is of course uncompromised..
Race Ready Front Suspension
A super-hard titanium coating on the outer surface of the inner fork tubes helps prevent wear abrasion. The fork’s surface hardness of the dark navy blue coating also helps to prevent scratches and damage to the tubes. Because the surface remains smooth for a longer period, sliding friction (and stiction) is reduced and action is improved, contributing to a smoother ride. (The KX250F is the only motocrosser in its class to feature this race-ready coating standard.)
Removing the damper assembly from the right fork tube frees up space for a pre-load adjuster. Having a preload adjuster simplifies the task of setting the fork preload or front height. The racer friendly SFF Type 2 also facilitates other maintainence chores like adjusting damping and changing springs.
Race Ready Rear Suspension
The rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately. A self-lubricating anodised coating on the tank cylinder helps prevent wear abrasion, and reduces friction for smoother suspension action.
Revised valve settings contribute to improved ride feel and increased rear-end feedback.
Rear shock spring 52 N/mm and the fine tuned damping settings offering greater composure when braking and accelerating.
Uni-Trak rear suspension system mounts the suspension arm below the swingarm, allowing a longer rear suspension stroke. The longer stroke in turn allows more precise rear suspension tuning. Extensive rider testing was conducted to determine the ideal linkage ratios and rear shock absorber damping settings to achieve maximum rear wheel traction.
For 2018, the ultra slim frame is one of the many components contributing to the KX250F’s trim form. The light weighing 2018 KX250F model is quicker both in the straights and through the corners. Suspension settings for the high-spec SFF Type 2 front fork and Uni-Trak rear shock were revised to deliver greater stability over braking bumps and through corners. A slim, flat rider interface further enhances the adjustable racer-friendly ergonomics, helping racers to rider even faster.
Oversize New Petal Disc
Large oversized 270mm front disc contributes to race winning braking power and control.
The radical design front and rear petal discs offer strong braking performance, excellent competitive edge with high quality factory looks.
Bridged Box Bottom Piston Design
High-performance piston, featuring the same design used on our factory racers, contributes to strong performance at all rpm. A short skirt, reinforced external ribs and the use of a bridged-box bottom, featuring internal bracing, contributes to a light, strong piston design. Already the lightest piston in its class, the pistons design and strength optimisation help lower reciprocating mass and contribute to the engine’s strong performance. Piston pin is offset 0.25 mm, complementing the offset cylinder and help reduce mechanical losses. Strength optimisation results in a light piston pin design. Coating and striation on the piston outer surface ensure good wear resistance and oil retention for minimal sliding friction. The molybdenum coating also helps reduce mechanical loss.
Easy engine tuning: DFI Setting Data Selection (3 map choices)
Adjusting engine settings to suit conditions has never been easier than with the KX’s FI couplers. Plug-and-play style system is quick, easy and stress-free. Instead of a single engine map, the ECU features three (four, counting the Launch Control Mode map). Initial settings for the three maps are: Standard (green), Hard (conditions)(black) and Soft (conditions)(white). Using provided FI couplers, riders are able to easily switch between the three maps to suit riding conditions. Plugging in each of the 4-pin couplers activates the corresponding engine map. (Plug is conveniently located on the right side of the head pipe for easy access without having to remove any parts.)
Each of the three maps can be reprogrammed using the optional KX FI Calibration Kit.
Precision engine tuning: KX FI Calibration Kit (Accessory)
The updated KX FI Calibration Kit features the handheld KX FI Calibration Controller, which enables expert riders to adjust engine characteristics (by rewriting actual data maps) to suit their preference. This simple tool can be used without a PC, simply by plugging into the engine’s ECU.
The KX FI Calibration Controller is handheld tool with a built in colour LCD screen. It comes with transfer and diagnostic cables, SD memory card, user manual and a carrying case.
Ask you Authorised Kawasaki Dealer for more information on this option.
The Holeshot Advantage: Launch Control Mode
The KX250F features a launch control system similar to that on our factory racers. With the simple press of a button, riders can activate a separate engine map designed to ensure efficient race starts in slippery conditions. The Launch Control Mode map retards ignition timing, allowing tyres to gain grip in low traction situations.
Launch Control Mode has the greatest effect within the first few seconds of releasing the clutch off the start. This is the most crucial time for the rider to get ahead of their rivals and line up the first corner.
To activate the Launch Control Mode riders depress the launch control button (for 2 seconds) located at the left handle. when activated the light next to the button will flash quickly to let the rider know it is on. Launch Control Mode works in 1st and 2nd gear. Once the rider shifts into 3rd gear, the system is automatically disengaged, switching back to the normal engine mapping.
43mm Throttle Body
43 mm throttle body is both compact and light. The main injector is now mounted at 30° in the throttle body and the FI settings have been optimised for the updated engine settings.
Designed specifically for motocrossers, the fuel injection system incorporates a small lightweight ECU and operates without a battery to further eliminate unnecessary weight. And of course, fuel injection eliminates the need to adjust engine settings to suit track and climate conditions
The 2018 KX250F new fuel pump, located in the fuel tank, is a lightweight aluminium construction. The fuel pump pressure has been increased from 294kPa to 343kPa.
Adjustable Handlebar Position
A choice of four positions allows riders to tailor their riding position. Factory-style Renthal handlebar and pad come standard.
Upper triple clamp with two sets of handle mount slots and reversible handle mounts offers riders a choice of four handle positions to choose from: 25 mm FWD, 15 mm FWD, STD and 10 mm BK.
Powerful, High-Revving, Dual Injection Engine with Factory-Style Tuning
Tuned to best suit race-experienced riders, the 249 cm3 liquid-cooled, 4-stroke Single’s wide power-band focuses on high-rpm performance and extends way into the over-rev. Highly acclaimed for its high output and smooth power delivery, the 2018 model KX250F backs up its dual-injected power and race-inspired tuning with a revised shorter downdraft-style intake duct and with a larger diameter and longer exhaust header pipe and with the intake camshafts timing is advanced by 6°, matched to the advance EFI system results in improved power/torque feeling make it easier to ride faster, enabling quicker lap times. Bottom-end to mid-range: The improved power/torque translates to smoother power engagement, making it easier to use the power band and requiring less attention to be spent on clutch work. Top-end: Thanks to the smoother power engagement, the high-rpm range is easier to use.
The use of the world’s first dual injectors for a production motocrosser is a key component of the KX250F’s highly acclaimed fuel-injected performance. Tuned for high performance, its high-revving character is complemented by superb response. For 2018, downdraft-style intake duct has been revised and is shorter to enhance the power and torque across the mid-top-end engine speed range.
The downstream injector is used to ensure smooth instant response while the upstream injector is chanrged with providing power. As RPM and throttle postion increase, primary operation switches from the downstream injector to the upstream injector.
Both fuel injection are fine atomising injectors with 4 holes, dispersing spray particles with a droplet size of 120 µm from the upstream injector and 75 µm fro the downstream injector. The downstream injector’s finer droplet size and wider spray angle contribute to stronger low-mid range power feeling, improved response and quicker acceleration.
Adjustable Footpeg Position
Riders can choose from two positions on the footpegs to suit their body size and personal preferences.
The adjustable brackets enable riders to lower the footpeg postion 5mm. In the lower position, centre of gravity is lowered as is the rider’s point of view, adding to both the physical and psychological stability.
Matching the KX250F’s light weight, the KX450F-inspired minimalist bodywork makes the bike look compact. Its shroud, fender and number plate designs ensure it is the sharpest looking bike in the paddock. Factory-style graphics further reflect the KX250F’s highly tuned performance, while the in-mould graphics give the design high durability. Green highlights on the suspension adjusters and engine oil cap and generator cover plugs contribute to a distinctive Kawasaki look.
- Kawasaki’s in-mould graphics used on the shrouds result in an ultra-smooth surface and ensure the racy graphics are not easily damaged.
- Sharp and aggressive design of the front fender adds to the racy appearance. The rear fender’s sharp design contributes to the overall design.
- Rims are coated in black alumite1–just like our factory racers.
- Fork and rear shock adjusters have a green alumite1 finish like our U.S. factory racers.
- Embossed Kawasaki logo on the clutch cover made to appear as the contact from your riding boots wears off the paint.
- Green finish on the oil cap and the two plugs on the generator cover further contribute to factory looks.
- Embossed design on the clutch cover designed to gradually appear as contact from riding boots wears off the paint.
- Engine covers are finished in silver paint, further reinforcing the KX250F’s factory image.
1 Alumite: an anodic oxidation finishing treatment for aluminium resulting in a coloured, corrosion/scratch-resistant film coating.
|Engine Type||4-stroke, liquid cooled, single cylinder|
|Bore x Stroke||77.0 x 53.6 mm|
|Valve System||DOHC, 4 valves|
|Fuel System||Fuel injection: ø43 mm x 1 with dual injectors|
|Clutch||Wet multi-disc, manual|
|Wheel travel – front||310 mm|
|Wheel travel – rear||310 mm|
|Tyre Size-front||80/100-21 (51M)|
|Tyre Size-rear||100/90-19 (57M)|
|Suspension – front||ø48 mm inverted telescopic Separate Function front Fork (SFF) Type 2, 22-way compression damping, 20-way rebound damping and 40-way spring preload adustability|
|Suspension – rear||Uni-Trak with adjustable dual-range (2 turns high speed / 19-way low-speed) compression damping, adjustable 22-way rebound damping and fully adjustable spring preload|
|Brakes – front||Single semi-floating 250 mm semi-floating petal disc with dual piston caliper.|
|Brakes – rear||Single 240 mm petal disc with single piston caliper.|
|L x W x H||2,172 x 825 x 1,270 mm|
|Ground Clearance||320 mm|
|Seat height||945 mm|
|Fuel capacity||6.3 litres|
|Curb Mass||104.7 kg (includes full fuel tank, all fluids at optimum levels)|