2009 Kawasaki KX250F Tech Briefing - Dirt Rider Magazine Online

Since Kawasaki built a Lites class four-stroke in 2004, only one bike has beat it for a national motocross championship: a Kawasaki KX125 with James Stewart in the saddle. In addition, the KX250F has won the lion's share of Lites SX championships as well. But Kawasaki didn't take that success as an excuse to rest on laurels. Instead Kawasaki engineers came up with an all-new KX250F for 2009. Starting with a new frame and swingarm, supported by enhanced suspension and powered by a new engine, the KX250F is a technical tour de force. For those who can't get enough of the nitty gritty of the technical side of MX, here is the detailed information that Kawasaki supplied to the press. It outlines every millimeter of change found in the '09 KX250F. Included in the KX250F Showa fork upgrades is a Lites-class first: titanium coated inner tubes.
This dark navy blue coating not only decreases stiction, but also provides a super-hard
surface to help prevent scratches and damage to the tubes.
The chassis is also major news, and is responsible for the KX250F's slimmer feel. A blend of forged, extruded and cast parts, the new frame uses fewer parts and gussets, is 2.2 lbs lighter than the 2008 model and is designed to provide enhanced stability with a better rigidity balance and improved drive from the rear tire. The main frame spars were reshaped and provide a 6mm narrower overall profile at the rider's knees. A new manufacturing process and downtube design shed weight, and work in harmony with relocated engine mounts to improve rigidity balance.
Working in conjunction with the frame revisions is a new aluminum swingarm now pivoting from a higher position on the frame for improved traction. It is a lighter, more tapered design with a "D" profile and a new cross bracket. A longer rear suspension stroke, and thus more precise rear suspension tuning, was achieved by mounting the suspension arm of the Uni-Trak(r) rear suspension system below the swingarm.
In addition to giving the KX250F a stunning new look; the completely revised bodywork was designed with rider comfort and ergonomics in mind. Offering the rider an even slimmer interface with natural positioning makes it easier for racers to stay relaxed and in control. Ergonomic enhancements include improved feel from the wider 50mm footpegs, a slimmer new seat design with firmer urethane foam, a non-slip top surface and smooth sides provides good seated grip and excellent rider mobility.2009 Kawasaki KX250F
Features and Benefits
All-new higher performing and more durable engine

- 249cc, liquid-cooled, four-stroke, four-valve, DOHC engine delivers hard-hitting power from mid-to-high-rpm- Engine oil capacity decreased from 1.5L on previous model to 1.0L, reducing overall weight and mechanical losses
New top end
- New cylinder head has revised intake ports for improved performance at all rpm, especially in the high-rpm range
- Special coating applied to the intake port cores during the casting process gives the intake ports extremely smooth surfaces and increased intake efficiency across the rev range
- Head gasket now silicon coated for improved sealing
- New cam chain tensioner spring reduces mechanical loss by approximately 30-percent
New intake and exhaust valves
- Formed from a new, highly rigid, titanium material, the lightweight 31mm intake and 25mm exhaust valves reduce reciprocating weight and offer greater high-rpm reliability
- Ultra-strong valves have extremely thin valve stems on par with those found in supersport machines with the intake valves featuring 0.25mm thicker heads for increased strength
New titanium exhaust pipe
- Tapered, expanding from approximately 35 to 45mm for better throttle response and performance at all rpm
- New silencer body shape to meet 99dB AMA noise regulations
New crankshaft balance
- A revised crank web significantly increases the crankshaft balance efficiency; it's now on par with the factory racers
- Results in reduced engine vibration, smoother power delivery and increased performance in the mid-high rpm rangeBetter cooling
- New 6.4mm wider radiators have a 6-percent larger capacity than previous model
- Very slim, high-capacity Denso radiators feature tightly packed cores and a fin design deliver superior cooling efficiency for excellent heat dispersion
- Radiator louvers increased from three to four and decreased in size and angle for less overlap and higher air flow
- Revised cylinder head water jacket routes coolant via the front of the cylinder head for a more even cooling performance
Improved transmission
- Ratchet drive shift mechanism replaces the previous models gear driven system for improved shift feel and durability
- Improved feel at the clutch lever by integrating the clutch cable holder with the crankcase
- Increasing the interval between gear shafts 1 mm further allows stronger gears to be used
- KX450F type crankcase oil filter added- Relocated scavenge oil filter screen (with new shape) can be accessed without splitting the crankcases, facilitating easier maintenance
- New clutch and generator covers for increased rigidity and better crash survivability
New aluminum perimeter frame
- Frame has a new 6mm slimmer overall width main spars shape - narrowing near the bend below the seat for a better riding position, then widening at the ankles to offer better grip
- Newly designed main, lower and gusset pieces around the fuel tank with revised cross sections
- Rigidity increased by moving upper engine mounts to sides of the head cover- New design is 2.2 lbs lighter than previous model
- Weight savings and rigidity balance aided by down tube with a smaller cast bracket that's now formed via a swaging (squeezing and hammering) process
- Swingarm pivot is located higher in the frame for improved rear wheel traction
- Sub-frame is 1.3 pounds lighter via larger diameter tubing with thinner walls, yet still provides a secure mounting for the new silencer
New aluminum swingarm
- New tapered "D" shaped cross section design is 5mm taller at the front (up from 74 to 79mm) and 2 mm shorter at the rear (down from 60 to 58mm)
- Features a new cross bracket design- Provides a 0.9 lbs weight savings over the previous model
- Alloy swingarm uses a cast front section, tapered hydroformed spars and forged chain adjusters
- Uni-Trak(r) rear suspension system mounts the suspension arm below the swingarm, allowing a longer rear suspension stroke and more precise tuning
- Design improves stability, rigidity and rear wheel traction
New front fork
- Showa twin-chamber fork keeps oil and air in separate chambers for stable damping performance during long motos
- Super-hard titanium coating on the outer surface of the inner fork tubes reduces stiction and improves suspension action. The increased surface hardness of the dark navy blue coating also helps prevent scratches and damage to the tubes
- Friction-reducing Kashima Coat on the inside of the outer fork tubes contributes to smoother suspension action, especially during the initial part of the stroke
- Ideal rigidity balance via increased rigidity in the reshaped upper triple clamp and decreased rigidity of the outer fork tubes
- Offset decreased from 24.5mm to 23.5mm, which combined with the frame's revised rigidity balance and revised suspension settings, helps produce lighter handling
- Enlarged, wrap around black fork tube guards provide greater protection for the inner tubes
- Revised race-oriented suspension settings offer all-around performance improvement
New rear shock
- New Showa rear shock features a revised layout and revised damping characteristics for improved performance- Better response and improved feeling, even when fully-bottomed
- Features Kashima Coat on the tank cylinder for reduced friction and smoother suspension action
- Rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately- Easier accessibility for tuning
New skid plate
- Resin material offers greater protection without a weight increaseNew chain guide
- More slim and compact, down from 42.7 to 34mm wide, with 2mm thicker wear pad- Reduced weight and longer wearImproved rider interface and styling
- Foot peg width (front to rear) increased from 46mm on previous model to 50mm for improved feel
- All-new body work and graphics- New dual injected 2-tone, one-piece plastic shrouds and side number plates
- Right side panel has an added passageway to aid in cooling the silencer
- Black plastic covers, triple clamps, number plates, and engine covers
- Rims are coated in black alumite - just like the factory racers
- New seat design that's slimmer with firmer urethane for improved ergonomics and feel
- Seat has a slip-resistant top surface for good grip when seated and smooth sides for excellent rider mobility
Additional features
- Larger front brake lever boot offers increased protection against dust
- Clutch cable boot features a large quick adjuster, for easy clutch cable play adjustment on the fly
- Throttle grip has a one-piece collar that provides additional stability during throttle operation
- Lightweight short-length grips feature a pattern designed to provide excellent grip
- Rear caliper guard protects the caliper from damage
- Ribless rear hub and butted spokes reduced unsprung weight

The new swingarm is more tapered. It is taller at the front and shorter at the back. It is also mounted higher in the frame and features a new cross bracket.
This is a cross-section of the 2008 frame spar design.
This is a cross-section (photo not to scale) of the shorter and narrower 2009 frame spar design.
The new chain guide.
This artsy-looking downtube is new as well. The '08 was blocky looking with two nearly 90-degree bends instead of this graceful "Y."
Now one-piece, the '09 radiator wings have less graphic area to get worn.
In addition to a trick slick and expensive coating for the inner fork tubes, the fork guards are now more protective.
This resin skid plate covers more than the old aluminum unit, and it should retain its shape better.
Kawasaki claims the crankshaft on the 250F now has a balance factor like the 2008 factory race bikes. The '09 is on the bottom and the '08 is on the top.
Kawasaki switched the 250F to a ratchet-type shifter (right) rather than the gear-type (left) used in previous models.
Previous KX250F models have used two filter screens (in addition to the replaceable oil filter) to protect the engine, but you had to split the cases to clean the filter screens. Now the main screen is under the ignition cover and easily cleaned.
Since 2004 the coolant has entered the engine at the top of the head on the right hand side (right), but for '09 (left) the coolant entering the engine from the radiators hits right above the exhaust port, then continues through the other coolant passages.
For 2009 the face of the titanium valves is a full 1mm thick rather than the .75mm used in 2008. That should improve valve train longevity.
The swingarm isn't the only new taper, the exhaust header tapers as well.
Port shape, design and finish are all improved for 2009 with an aim of better power.
This is the first innovation in radiator louvers we have seen in a while. The four shorter slats protect, but don't shroud the cores as much as three larger slats.