2010 Kawasaki 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
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
- 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),
- 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
clearance. These changes offer increased shifting
- Crankcases with revised engine mounts and increased
thickness are stronger, contributing to enhanced
- 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
- 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.
additional control facilitates corner entry.