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2010 Kawasaki KX250F

2010 Kawasaki KX250F2010 KX250F

Already ranked at the top of its class in numerous enthusiast magazine shootouts, further fine-tuning of the KX250F’s engine and chassis ensures its winning performance is maintained for 2010.

The KX250F base package provides an excellent platform for race-experienced riders to win races in the top classes. Design of the highly rigid aluminium frame, suspension components and settings focused on delivering superb high-speed stability – 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 further increased the KX250F’s winning potential. Straight from the racing world, a new piston with bridged-box bottom makes its first appearance in a mass-production machine. Other modifications offer increased performance and enhanced durability and reliability.

Updates to the chassis include changes to swingarm and suspension for increased cornering performance and an optimised front-rear balance that contributes to enhanced stability on corner entry.

Already acclaimed as the best looking motocrosser in the paddock, the KX250F once again sports sharp factory-racer looks that are more than skin deep. Sleek, functional bodywork was designed to offer racers a slim rider interface to further facilitate going faster.

The new KX250F – still giving racers the competitive edge to stay out front.

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. For 2010, a number of refinements, including the first mass-production use of a high-performance piston featuring a bridged-box bottom, offer improved performance and enhanced durability and reliability.

  • 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.
  • Wider (18 mm >> 19 mm) big-end bearing featuring thicker copper plating on its cage, and a longer crank pin offer increased reliability.
  • Revised oil pump rotors offer increased reliability and durability. Feed pump rotor size is larger (5 mm >> 5.5 mm), increasing oil flow; scavenge pump rotor is smaller (11 mm >> 10.5 mm), reducing
    mechanical loss.
  • Larger dogs on the 3rd and 4th input gears help prevent wear, and revising the 4th input gear holding method (by eliminating a circlip and washer and changing the shape of the 2nd input gear) reduces thrust
    clearance. These changes offer increased shifting reliability.
  • Crankcases with revised engine mounts and increased thickness are stronger, contributing to enhanced durability.
  • New thicker (22 mm >> 32 mm), wider (113.8 mm >> 117.8 mm) radiators with increased fin and tube pitch are stronger, offer better resistance to mud build-up, and maintain cooling performance. Because the new radiators are stronger, reinforcing brackets could be eliminated, resulting in lower overall weight. (These radiators feature the same construction as those on the 10MY KX450F.)
  • Exhaust pipe’s new stainless steel construction is more durable. Revised joint between the exhaust pipe and muffler offers increased sealing performance. Rubber damper collar used for the rear silencer
    mount also contributes to increased durability.

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 new, 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 ’10 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.
  • 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.