2009 KX250F Kawasaki

The 2009 KX250F Kawasaki features a number major changes, with the engine receiving a new cylinder, cylinder head, piston, and cases.

The new for 09 aluminium frame is lighter and slimmer with straight line stability a goal. Forks have gotten a coating of low friction  titanium. Swingarm and rear suspension are tweaked, and a host of other changes include slimmer bodywork, more efficient radiator design, and wider pegs.

Engine 

Tuned to best suit race-experienced riders, the 249 cm3 liquid-cooled, 4-stroke Single’s wide powerband focuses on high-rpm performance and extends way into the over-rev.

’09 engine modifications focus on further improving performance in the high-rpm and over-run ranges as well as ensuring sharper response. Revised lubrication improves both performance and reliability; changes to the transmission improve shift touch and clutch feel

* New cylinder head has revised intake ports for improved performance at all rpm (especially
in the high-rpm range).

* During the cylinder head casting process, the cores for the intake ports were given a
special coating to make the intake ports smoother. The extremely smooth surfaces that
result increase intake efficiency across the rev range.



* Revised cylinder head water jacket routes coolant via the front of the cylinder head for
more even cooling performance.

* New titanium exhaust pipe is tapered, expanding from 35 mm to 45 mm. Designed to
increase performance at both low and high rpm, the new exhaust pipe offers improved
throttle response at all rpm.

* Changing the cam chain tensioner spring to one with lower load (44 N >> 31 N) reduces
mechanical loss by approximately 30%.

* A revised crank web increases offsetting moment for significantly increased crankshaft
balance factor. At close to 60% (compared to 45% for the ’08 model), the balance
factor of the ’09 KX250F is on par with our factory racers. The result is reduced engine
vibration, smoother power delivery and increased performance in the mid-high rpm range.

* High-capacity Denso radiators deliver superior cooling efficiency. The radiators are very
slim and feature tightly packed cores and a fin design for excellent heat dissipation.

* Increased radiator capacity (6%) comes care of 6.4 mm wider radiators

*Revised radiator louver design better directs cooling air to the radiators.

* Revised ignition timing improves feeling at low-mid rpm.

* A reduction in engine oil (1.5 L >> 1.0 L) contributes to overall weight reduction and reduces mechanical loss in the      transmission. Smoother shifting

* Newly designed gear shift mechanism offers improved shift feeling. Where the previous model used a gear driven system, the ’09 KX250F features a ratchet drive system (like that on the KX450F). Lever ratios, spring rates and shaft locations were all reevaluated.

* Clutch cable holder is now unitised with the crankcase. The increased rigidity results in improved feel at the clutch lever.

* 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 new, highly rigid, titanium material.

* Transmission shafts are now spaced 1 mm further apart, allowing stronger gears to be used. A new oil passage in the crankcase (supplied by the scavenging pump) creates an oil shower, ensuring more effective lubrication of the transmission gears.

* 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.

Chassis

The KX250F’s slim aluminium 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 ’09 revisions to the frame and suspension components were designed to offer greater manageability in tight corners while maintaining high-speed straight-line stability, lighter handling overall and a slimmer package

*Upper engine mounts moved from directly over the engine to sides of the cylinder head, increasing rigidity.

* Newly designed main pipes, lower pipes and gusset pipes around the fuel tank feature revised cross sections.

* The down tube is now formed with a swaging (squeezing and hammering) process and has a smaller cast bracket, further contributing to both weight savings and the revised rigidity balance.

* Lower cross pipe is now common with the KX450F.

* Altogether, the parts revisions combine to give a weight savings of approximately 1 kg.

* New swingarm has revised rigidity, which contributes to improved riding stability, and is approximately 400 g lighter.

* Swingarm construction is basically the same as that of the ’08 model, but is more tapered than before and has a slightly D-shaped cross section.

* The alloy swingarm uses a cast front section, tapered hydroformed spars and forged chain adjusters.

* The swingarm pivot is located higher in the frame for improved 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. Superior rear-wheel traction

* Showa twin-chamber fork keeps oil and air in separate chambers for stable damping performance during long motos. Revised damping settings for ’09 contribute to lighter handling and improved ride feel.

*Aluminium instead of steel is used on a number of components in order to save weight: the fuel tank fitting nuts, the seat mounting brackets, the front brake hose clamp. The upper mounting brackets for the plastic fork slider. protectors were also eliminated.

* Beefier sub-frame complements the heavier new muffler.

* Larger synthetic skid plate replaces the small aluminium unit. The new skid plate offers greater protection without increasing weight.

* Larger front brake lever boot offers increased protection against dust.

Rider interface

In addition to giving the ’09 KX250F a stunning new look, completely revised bodywork was all designed with rider ergonomics in mind. The new components offer the rider an even slimmer interface, the natural position making it even easier for racers to go fast.

* New frame is approximately 6 mm slimmer across the main pipes.

* Formed using a double-injection moulding process, the new 2-tone shrouds contribute to a slimmer package. Fuel tank also revised accordingly

* 2-tone side covers are also formed using a double-injection moulding process. Like the shrouds they contribute to the slimmer 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.

* New seat is slimmer and features a harder urethane for optimum rider ergonomics.

* The seat uses a slip-resistant top surface for good grip when seated and smooth sides for excellent rider mobility.

* New wider (front to rear) footpegs (46 mm >> 50 mm) offer riders increased grip as well as improved 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.

Click on this image for a graphical map of key changes to the 2009 Kawasaki KX250F.

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Specifications 2009 KX250F