2010 Kawasaki KX250F dirt bike
The Kawasaki KX250F dirt bike’s 249cc, liquid-cooled, 4-stroke single-cylinder DOHC, 4-valve power-plant has received a number of refinements that enhance an already potent package.
Making its first appearance in a mass-production motorcycle, the KX250F dirt bike receives a “bridged-box bottom” race-inspired piston, which is lighter and stronger due supporting ribs that reinforce the piston pin shaft.
The new piston has a shorter skirt and narrower piston pin to reduce reciprocating mass, resulting in a quicker revving motor. The piston’s crown has been reshaped, adding 0.6mm in height to improve combustion with the cylinder height increased slightly to maintain a 13.2:1 compression ratio.
Kawasaki implemented an “electro-fusion treatment” on the cylinder bore for better oil retention and less scorching, thus making the top-end more resistant to seizing. These top-end changes, coupled with new, wider (from 5mm to 5.5mm) oil pump rotors – that have increased oil flow by 10% – and a wider big-end rod bearing are specifically aimed at extending engine life and increasing reliability. The technicians at
Kawasaki boast that they’ve gotten the KX’s crankshaft balance closer to that of the factory racers, resulting in less vibration, which translates into smoother throttle response.
- 2010 KX250F Forks
On the transmission end of the KX250F dirt bike , beefier dogs were added to the 3rd and 4th input gears to reduce wear while the cir-clip and washer of the 4th input gear holding method was eliminated by redesigning the 2nd input gear to carry the weight load instead of the washer.
The result of these changes is increased precision of the shifts with added strength and durability. The five-speed transmission enlists the same ratios as last year. Crankcases have been thickened overall with added material at crucial engine mounting holes.
Showa twin-chamber forks have titanium-coated lower tubes that reduce friction for smoother response. The 16-way compression and rebound damping adjustments augment 12.4 inches of fork travel. The damping settings are new, with less forward lean that lends more balance in the bike’s front to rear attitude.
The new damping settings on the Showa rear shock combined with the new rocker arm are implemented to reduce kicking on corner entry. The rear shock possesses 13-way low-speed and step-less high-speed compression damping with 17-position rebound damping and fully adjustable spring preload, providing 12.2 inches of rear wheel travel of the dirt bike.