Key Kawasaki KX 250F Technology
Factory Tuning, FI to Keep Expert Riders at the Front of the Pack
The KX250F base package provides an excellent platform for race-experienced riders to win races in the top classes. Design of the highly rigid aluminum frame, suspension components and settings focused on ensuring control is maintained during high-speed riding – especially in straight lines – to enable experienced racers to ride full out. And to deliver holeshot-winning performance – a key factor that can mean the difference between running up front and winning, or getting stuck mid-pack – chassis geometry and the high-revving 4-stroke engine’s wide powerband were designed to maximise rear wheel traction. The combination is a proven race-winner, with multiple AMA Supercross Lites and Motocross Lites championships to its credit.
To ensure the Lime Green racers continue to run at the front, Kawasaki engineers made a number of engine and chassis changes to further increase the KX250F’s winning potential.
More powerful, fuel-injected engine with factory tuning
- specs on par with our factory racers
- Tuned to best suit race-experienced riders, the 249 cc liquid-cooled, 4-stroke Single’s wide powerband focuses on high-rpm performance and extends way into the over-rev.
- quick throttle response
- superb over-rev characteristics
- Tuned for high performance, the wide powerband extends way into the over-rev. A works-base bridged-box bottom piston (used for the first time on a mass-production motocrosser on the 10MY KX250F) is just one of many features inspired by our factory racers.
- NEW To ensure the high-rpm engine’s demand for a high flow of gas in a short period is met, the KX250F’s injector features larger holes than that used on the KX450F. A fine atomising injector with 4 holes disperses spray particles with a droplet size of 120µm. Fuel flow is about 20% greater than on the KX450F.
- NEW stronger low-mid torque allows riders to corner a gear higher (less shifting)
- NEW KX FI Calibration Kit (option) identical to that used by our factory teams
- NEW exhaust revisions to meet stricter noise regulations
High-speed chassis with factory-style components and tuning
- NEW Showa’s Separate Function front Fork (SFF)
- Left fork tube: damping assembly
- Right fork tube: spring
Benefits include:
- With only one spring, the friction generated between the spring(s) and fork inner tube(s) is greatly reduced (approximately 25% less)
- Removing the damper assembly from the right fork tube frees up space for a preload adjuster.
- racer friendly: suspension jobs are quicker & easier
- improved left/right balance
- NEW chassis fine-tuning for revised rigidity balance results in increased lateral chassis flex
Benefits include:
- lighter turning
- increased rear wheel traction
- more planted feel from front wheel
- enhanced cornering accuracy
- control maintained during high-speed riding (in straights and when cornering)
Factory styling
- NEW aggressive graphics
- blacked-out rims
- NEW Fork and rear shock adjusters have a blue alumite1 finish
At-A Glance
NEW 249 cc liquid-cooled, 4-stroke Single with fuel injection
Tuned to best suit race-experienced riders, the 249 cc liquid-cooled, 4-stroke Single’s wide powerband focuses on high-rpm performance and extends way into the over-rev.
Factory-inspired tuning
Tuned for high performance, the wide powerband extends way into the over-rev. A works-base bridged-box bottom piston (used for the first time on a mass-production motocrosser on the 10MY KX250F) is just one of many features inspired by our factory racers.
NEW Progressive throttle link
A 43 mm throttle body makes use of a progressive throttle link to deliver airflow in much the same way as would a FCR carburettor. Using two linked shafts, the throttle body opens more quickly after the 3/8 open position, delivering sharp response and excellent power feeling.
NEW Setting-adjustable motocross ECU
The KX FI Calibration Kit contains KX Racing software, an ECU controller, mounting brackets and damper, harness and USB cable. In addition to the kit, a PC and 12 V battery are all that is required.
NEW Less mis-shifts
Shift mechanism revisions offer more accurate shifting.
NEW Reduced noise
Changes to silencer internals ensure that stricter noise regulations are met.
All-aluminum perimeter frame
Slim aluminum perimeter frame is a lightweight construction composed of forged, extruded and cast parts.
NEW Lighter-handling chassis
Increased chassis flex, revised rigidity balance and reduced fork offset result in lighter turning, increased rear wheel traction, a more planted feel from the front wheel and enhanced cornering accuracy.
New Uni-Trak rear suspension
Linkage mounts below the swingarm for more precise suspension tuning.
NEW Separate Function front Fork (SFF)
Showa’s Separate Function front Fork (SFF)
NEW Rear shock absorber
Rear shock damping settings, revised to match the new SFF, offer improved action and increased absorption performance.
Renthal handlebar
A factory-style Renthal (standard-type) aluminum handlebar is standard equipment.
Slim rider interface
Bodywork components and seat designed to offer a slim, natural riding position making it easier for racers to go fast.
NEW Seat
Revised pattern for the seat sides offers more grip.
Petal brake discs
Among the KX250F’s numerous factory-style components are its front and rear petal disc brakes.
NEW Factory styling
Fork and rear shock adjusters
Key Features
Powerful, High-Revving Fuel-Injected Engine with Factory-Style Tuning
Tuned to best suit race-experienced riders, the 249 cc liquid-cooled, 4-stroke Single’s wide powerband focuses on high-rpm performance and extends way into the over-rev. Already featuring race-inspired tuning and parts like the high-performance piston with bridged-box bottom (a mass-production first when introduced on the 2010 KX250F), the 2011 engine receives fuel injection and a number of changes for even more power, stronger low-mid range torque (most noticeable when riding through the whoops, landing jumps and coming out of tight turns, it allows riders to shift less often, reducing fatigue and enabling quicker lap times), more accurate shifting and a quieter exhaust note.
Factory-racer engine tuning
- High-performance piston, featuring the same design used on our factory racers, contributes to improved performance at all rpm, A short skirt, reinforced external ribs and the industry’s only mass-production use of a bridged-box bottom, featuring fully flush internal bracing, result in a lighter, stronger piston.
NEW - A new piston crown, revised to suit chamfering of the squish area, offers increased high-rpm and over-rev performance.
NEW - Intake camshaft with revised sprocket/shaft arrangement retards intake valve timing 1o, to suit the new fuel-injected engine.
10MY 11MY
Open 41o BTDC 40o BTDC
Close 71o ABDC 72o ABDC
Valve lift was also increased (8.7 mm >> 9.3 mm) and, accordingly, stronger valve springs were used.
NEW - A new spark plug protrudes 1.4 mm deeper into the combustion chamber, improving combustion efficiency.
NEW - Intake ducting has about 10% greater volume, resulting in improved response (especially in the ultra-low rpm range).
NEW - The revised intake ducting and new deep-protrusion spark plug not only offset the drop in low-mid torque that comes from a change to fuel injection, performance is actually improved in this range.
NEW - Revised final reduction ratio offers improved engine feel. The shorter gearing (13/48T >> 13/50T) further accentuates the increased low-end torque.
NEW - Cylinder height reduced (36.5 mm >> 36.3 mm) to suit the new piston and higher compression ratio: now 13.5:1 (previously 13.2:1).
NEW - Exhaust pipe is longer (480 mm >> 510 mm) to suit new engine characteristics.
Battery-less fuel injection system
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.
NEW - Ensuring quick starting without a battery was a prime directive when developing this fuel injection system. Using only electricity generated by the kick starter, the engine can be started with only three rotations of the crankshaft. The system delivers electricity in the following order: 1) ECU, 2) fuel pump, 3) injector. With a warm engine, starting can be accomplished in a single kick.
NEW - The compact, lightweight ECU, located just in front of the steering head (behind the number plate), was designed specifically for motocross use. To help cope with the shocks and vibrations of motocross riding, the fuel pump relay is built in to the ECU.
NEW - A 43 mm throttle body makes use of a progressive throttle link to deliver airflow in much the same way as would a FCR carburettor. Using two linked shafts, the throttle body opens more quickly after the 3/8 open position, delivering sharp response and excellent power feeling.
NEW - Lightweight throttle body is approximately half the weight of a FCR carburettor – a weight savings of about 600 g.
NEW - To ensure the high-rpm engine’s demand for a high flow of gas in a short period is met, the KX250F’s injector features larger holes than that used on the KX450F. A fine atomising injector with 4 holes disperses spray particles with a droplet size of 120µm. Fuel flow is about 20% greater than on the KX450F.
NEW - The newly designed fuel pump, located in the fuel tank, is a lightweight aluminum construction. (Fuel tank capacity is now 7.2 litres.)
NEW - To ensure a stable fuel supply during vigorous motocross riding the fuel pump features a rubber fuel filter cover that wraps around the inlet port and acts as a fuel trap. A fuel return hose from the pressure regulator ensures there is always fuel in the fuel trap.
Factory KX FI Calibration Kit (optional part # 99999-0289)
The KX FI Calibration Kit is the same kit used by Kawasaki’s works teams in Europe and the U.S. The kit enables expert riders to adjust engine characteristics (by rewriting actual data maps) to suit their preference, record riding data, and analyze their riding data to further fine-tune their settings.
NEW - The KX FI Calibration Kit contains KX Racing software, an ECU controller, mounting brackets and damper, harness and USB cable. In addition to the kit, a PC and 12 V battery are all that is required.
NEW - While the kit is designed to satisfy racers and expert riders, it is simple and hassle-free to use:
- the ECU controller mounts behind the number plate for easy access
- accessing the ECU is accomplished simply by connecting to a PC via the ECU controller using a USB cable (no additional switches are necessary)
- setting adjustments can be prepared in advance on a PC, or done when connected to the ECU
- the kit’s user-interface is simple to understand and easy to use
NEW - The KX FI Calibration Kit contains seven preset settings that can be quickly and easily used to adjust the ECU to suit track conditions. The provided settings are shown below.
SETTING DESCRIPTION
Richer fuel setting fuelling 5% richer than stock
Leaner fuel setting fuelling 5% leaner than stock
Advanced ignition setting ignition advanced 3° from stock
Retarded ignition setting ignition retarded 3° from stock
Hard riding surface setting ignition retarded, fuelling richer
Soft riding surface setting ignition retarded, fuelling richer
Beginner setting engine power suppressed:
ignition retarded, fuelling richer
NEW - For more advanced setting optimisation, the ECU maps for volume of fuel injected (via the FI adjustment window) and ignition timing (via the IG adjustment window) can be adjusted for given throttle position and rpm.
- Base settings are shown as a flat graph. Settings can be increased or decreased from the base according to rider preference.
NEW - Multiple display options are available. Click [3D Graph] or [2D Graph] of the [3D/2D] to select the 3 or 2-dimensional display. When you use the [3D Graph], select [Surface Display] or [Frame Display] of the [3D Graph Type] to select the display type.
NEW - Both click-and-drag (using the graph window) and numerical editing (using the map sheet) are possible.
NEW - When connected to the ECU, the KX FI Calibration Kit can be used to display the status of a running engine. Information can be displayed in numeric form using the Data Monitor , or in visual form using the various display options offered by the Data Meter.
NEW - The KX FI Calibration Kit can also be used as a data logger, recording up to six hours of data depending on the number of parameters (engine rpm, angle of throttle opening, etc) being recorded. After riding, the riding data can be viewed using the [Analyze] window . Parameters to be recorded and displayed can be selected independently.
NEW - The logged data can lined up with the course layout to check actual riding, enabling more efficient FI settings to be determined. It also enables before-and-after comparisons and comparisons between riders.
For more detailed information on use and functions of the FI Calibration Kit, please refer to the KX FI Calibration Kit Instruction Manual.
Less mis-shifts
NEW - A longer ratchet lever causes the ratchet to turn a greater amount with each shift (53° >> 60°), reducing the chance of mis-shift.
NEW - A lighter ratchet lever return spring ensures that shift lever weight feel remains the same.
Reduced noise
NEW - On North American models, revised internal construction results in a quieter silencer that clears stricter 94 dB noise regulations.
Additional performance-oriented engine characteristics
- The engine was tuned such that the torque curve follows the limit of running resistance for as long as possible. (Unchecked, engine torque can exceed this limit, resulting in wheel spin, which does nothing to help forward momentum.)
- Efforts were made to achieve the widest possible torque band, so that traction efficiency would be maximised for a greater part of the rev range.
- Lightweight titanium valves (IN: 31 mm; EX: 25 mm) reduce reciprocating weight and offer high-rpm reliability. The ultra-light valves have extremely thin valve stems on par with those found in supersport machines. The intake valves feature thicker heads for increased strength and both intake and exhaust valves are formed from a highly rigid, titanium material.
- Crank web design increases offsetting moment for a high crankshaft balance factor. At close to 60%, the balance factor of the ’11 KX250F is on par with our factory racers. The high balance factor contributes to reduced engine vibration, smoother power delivery and increased performance in the mid-high rpm range.
- 32 mm thick, 117.8 mm wide radiators with wide fin and tube pitch offer resistance to mud build-up while maintain cooling performance. The radiators are strong enough that the reinforcing brackets could be eliminated, resulting in lower overall weight.
- Sprocket-style chain drive roller helps smooth engine braking by reducing the effect of driveline lash when the rider gets off the gas quickly and play in the lower side of the chain suddenly tightens. The additional control facilitates corner entry.
High-Speed Chassis with Factory-Style Components and Tuning
The KX250F’s slim aluminum perimeter frame is a lightweight construction composed of forged, extruded and cast parts. Chassis balance and settings were all set to suit race-experienced riders. The centre of gravity and key dimensions (swingarm pivot, output sprocket and rear axle locations) were chosen so that the rear tyre would drive the bike forward (instead of causing it to squat). For ’11 the high-speed chassis benefits from a new Separate Function front Fork (SFF) with greatly reduced friction that offers increased riding comfort and improved suspension performance. In addition to enhanced handling offered by the SFF’s improved left/right balance, increased chassis flex and revised frame rigidity balance offer lighter handling and increased turning performance. The highly acclaimed high-speed stability of its predecessor remains unchanged.
Lighter-handling chassis
While the frame remains essentially the same as that of the 10MY model, revised rigidity balance results in a frame with moderate lateral flex.
NEW - Frame’s front and side hangers (engine mounting brackets), previously aluminum, are now formed from steel, and are thinner (front: t6.0 mm >> t4.5 mm; side: t8.0 mm >> t4.5 mm).
NEW - The resultant increased lateral chassis flex enables lighter turning.
NEW - The revised rigidity balance offers a number of benefits:
- increased rear wheel traction
- more planted feel from the front wheel
- enhanced cornering accuracy makes it easier for riders to follow the line they want
NEW - Reduced fork offset (23.5 mm >> 22.5 mm) also contributes to the lighter handling, enhanced cornering accuracy and more planted feel of the front wheel. Additionally, it also gives the bike a more compact feel.
Superior rear-wheel traction
- The New 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.
Race-oriented suspension: Separate Function front Fork
Showa’s Separate Function front Fork (SFF) makes its first appearance on a mass-production motocrosser. The SFF 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.
NEW - 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.
NEW - Being able to use a larger damper piston not only enables smoother action, it also makes firm damping performance possible.
NEW - Removing the damper assembly from the right fork tube frees up space for a preload adjuster. Having a preload adjuster greater simplifies the task of setting fork preload or front height. (With a conventional fork, only the rear could be adjusted easily; adjusting the front required fork tubes to be disassembled and the use of collars and special tools. With SFF, both the front and rear preload/height can be set quickly and easily.)
NEW - In addition to preload adjustment, the racer-friendly SFF also facilitates other maintenance chores like adjusting damping and changing springs.
MAINTENANCE JOB STD SFF
Adjust preload: Collars needed Y Adjust via dial
Adjust preload: Remove & disassemble Y -
Adjust preload: Special tools Y -
Adjust damping: Places 4 2
Change spring rate: Remove fork x2 -
Change spring rate: Disassemble x2 x1
Change spring rate: Special tools Y -
Change spring rate: Number of springs 2 1
NEW - SFF offers improved left/right balance, which greatly enhances handling. Locating the heavy spring in the right tube (and fine-tuning the left and right tube strength) better offsets the previously unbalanced weight of the brake caliper and disc on the left side.
NEW - A restrictor added on the damper assembly side and a joint rod comp added on the spring side ensure that natural character is maintained. Placement of the restrictor can be used to change damping characteristics; it contributes to idealised damping character. The joint rod comp ensures even left/right damping force and contributes to ideal fork rigidity.
- A super-hard titanium coating on the outer surface of the inner fork tubes reduces sliding friction (and stiction) and improves action, contributing to the smoother ride. The increased surface hardness of the dark navy blue coating also helps to prevent scratches and damage to the tubes. (The KX250F is the only motocrosser in its class to feature this race-ready coating standard.)
- Friction-reducing Kashima Coat on the inside of the fork outer tubes contributes to smoother suspension action (especially at the initial part of the stroke) and a better ride feel.
Race-oriented rear suspension
NEW - Rear shock damping settings, revised to match the new SFF, offer improved action and increased absorption performance.
- The rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately.
- The rear shock also features the Kashima Coat on the tank cylinder. The reduced friction smoothes suspension action.
Factory-style and other race-oriented components
- Among the KX250F’s numerous factory-style components are its front and rear petal disc brakes. In addition to helping reduce unsprung weight, the wave shapes of the petal discs help clean the brake pads for more efficient braking performance.
- Rear caliper guard protects the caliper from damage.
- A factory-style Renthal (standard-type) aluminum handlebar is standard equipment.
- Rib-less rear hub and butted spokes reduced unsprung weight.
- Rims are coated in black alumite1 – just like our factory racers.
NEW - Fork and rear shock adjusters have a blue alumite1 finish like our US factory racers.
- Factory-style graphics complement the KX250F’s highly tuned performance.
Rider interface
Designed with rider ergonomics in mind, bodywork components offer the rider a slim interface, the natural position making it even easier for racers to go fast.
- Formed using a double-injection moulding process, 2-tone shrouds contribute to the slim package.
- 2-tone side covers are also formed using a double-injection moulding process. Like the shrouds they contribute to the slim package. A hole in the right-side cover helps cool the silencer.
- The frame widens at the ankles to offer the rider better grip and narrows near the bend below the seat to allow a slim riding position.
- The seat uses a slip-resistant top surface for good grip when seated and smooth sides for excellent rider mobility.
NEW - Revised pattern for the seat sides offer more grip than before.
- Seat urethane designed to keep the original shape longer.
- Wide (front-to-rear) footpegs designed to offer grip and superb feel at the pegs.
- The clutch cable boot features a large quick adjuster, making it easier for riders to adjust play in the clutch cable.
- Throttle grip has a unitised collar. The one-piece unit provides additional stability during throttle operation.
- Lightweight short-length grips feature a pattern designed to provide excellent grip.
Engine
- Electrofusion treatment on cylinder bore results in a surface with good oil retention. Further, the molybdenum on the surface of the cylinder bore helps resist scorching, contributing to durability.
Chassis
- The alloy swingarm uses a cast front section, tapered hydroformed spars and forged chain adjusters.
NEW - Swingarm is longer to accommodate the larger rear sprocket, and is now common with the KX450F. The chain is also longer: 112 links >> 114 links.
- Large synthetic skid plate offers great protection with minimum weight.
NEW - Front chain guide (chain slider) uses a thicker plastic lining, offering longer wear life.
Other
- Optional engine parts include magneto rotors with different inertias (8.5, 9.5 kgøcm2; STD: 9.0 kgøcm2) and a 12T output sprocket (STD: 13T).
- Optional chassis parts include handlebar holder for a f28.6 mm bar (STD: f22.2 mm), aluminum and steel rear sprockets (48-52T; STD: 50T), solid petal brake rotors for wet races, and different springs for the front fork (8.7, 9.1, 9.5 N/mm; STD: 9.1 N/mm) and rear shock (47, 48.1, 49, 50, 51, 52, 53, 53.9 N/mm, STD: 51 N/mm).
NEW - An FI indicator lamp (optional part # 23016-0049) warns of any problem with the FI system.
Colours- Lime Green with new factory-style graphics
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