2011 Kawasaki KX250F | Features Video

MX Bike Video

For 2011, the goal was an even faster and more ridable Kawasaki KX250F. On the more powerful side of the equation are loads of engine modifications, all of which have made the latest KX an absolute corner-to-corner screamer.

The big news is the addition of Digital Fuel Injection (DFI) that not only helps produce stunning – and more useable – power, but also makes tuning a much easier proposition.

The system, basically identical to the one fitted to the 2011 KX450F, automatically adjusts to suit track and climate conditions, and offers consistent fuel metering and response even when the going gets rough, such as when landing off jumps or slamming through the whoops.

The simple and highly efficient DFI system incorporates a compact and lightweight Electronic Control Unit (ECU), a 43mm throttle body, a lightweight aluminum fuel pump and an ultra-fine atomizing injector.

Set at a 45-degree angle for optimum mid-range power, the injector precisely metered fuel directly into the intake tract for smooth power delivery and highly accurate engine response throughout the entire rpm range.

The 250F’s injector actually flows more fuel than the 450F’s unit due to the 250F engine’s higher speeds, while airflow through the system is actually higher than through the 2010 model’s carburetor setup. 

At a Glance…

• New Digital Fuel Injection (DFI) system

• New Showa

Separate Function Fork (SFF) divides spring and damping functions;

springing in the right leg and damping in left provide less friction,

better performance and easier adjustability

• Increased

engine performance via higher compression and exhaust/intake changes


High-performance piston featuring Bridged Box-bottom design

• Stainless

steel exhaust features longer header section and larger-volume muffler

• Revised

suspension settings front and rear aimed at race-experienced riders

Higher Performing, High-revving Engine

• 249cc, liquid-cooled, four-stroke, four-valve, single-cylinder

DOHC engine delivers hard-hitting power across the rpm range

• Modified

intake valve timing and cam profile for increased valve lift improves

high-rpm power production

• Intake

valve spring tension increased to control more radical cam timing

• Digital

Fuel Injection (DFI) system allows consistent fuel delivery, quick

starts and easy adjustability

• Engine

tuned to achieve the widest possible torque band to maximize traction

through a greater percentage of the rev range


Race-experienced riders able to harness high-rpm performance that

extends way into the over-rev


Sprocket-style chain drive roller helps reduce the effect of driveline

lash and engine braking for smoother and faster corner entries

• Crank web

design features a balance factor on par with the factory racers for

reduced engine vibration, smoother power delivery and increased

performance in the mid-high rpm range

Digital Fuel Injection (DFI) System

• Same basic system that’s fitted to the KX450F

• 43mm

throttle body assembly with 20 percent higher-flow injector than the

KX450F’s injector

• Intake

airflow is higher than on carburetor-equipped 2010 model

• Progressive

throttle link; opens more quickly after 3/8 open position

• Simple and

efficient system: No battery, fuses or relays

• Improves

engine response across entire rpm range

• Offers easy

engine starting

• Prevents

engine hesitation after landing from jumps and other high-impact

situations

• Optional

Calibration Kit allows easy tunability

• Optional FI

Indicator Light allows the DFI system to communicate diagnostic

information

Bridged Box-bottom Piston

• Light and strong piston shares same design as the factory

racers, with a revised crown for higher compression. Also features fully

flush internal bracing

• Short

piston pin reduces reciprocating weight

Lightweight and Efficient Top End

• Lightweight, highly rigid, titanium 31mm intake and 25mm

exhaust valves reduce reciprocating weight and offer high-rpm

reliability

• Ultra-light

valves have extremely thin valve stems on par with those found in

supersport machines; intake valves feature thick heads for increased

strength

• Intake

ports designed for peak performance at all rpm, especially in the

high-rpm range

• Special

coating applied to intake port cores during casting gives the intake

ports extremely smooth surfaces and optimum intake efficiency across the

rev range


Silicon-coated head gasket provides excellent sealing

Enhanced Durability and Reliability

• Electrofusion treatment on cylinder bore improves surface oil

retention, while the molybdenum coating on the cylinder bore surface

helps resist scorching, further contributing to durability

• Wide

big-end bearing features a thick copper plate on its cage and a long

crank pin for increased reliability

• Oil pump

rotors offer a high degree of reliability and durability; a large feed

pump rotor maximizes oil flow, while a smaller scavenge-pump rotor

reduces mechanical losses

New Stainless Steel Exhaust System

• Stainless steel construction offers extra durability

• Longer

header pipe section for improved low and mid-range response


Higher-volume muffler assembly quiets emissions to 94 dB noise

regulations while retaining power production

• Joint

between pipe and muffler offers excellent sealing, while a rubber damper

collar on the rear silencer mount equals serious durability

Efficient Cooling System

• Thick and wide radiators are strong and offer excellent

resistance to mud buildup while providing superb cooling performance

• Cylinder

head water jacket routes coolant to the front of the cylinder head for

even cooling

Transmission and Shifting Reliability

• Third and fourth input gears have large dogs to help prevent

wear

• Revised

ratchet and lever angle for more positive shifting

• Revised

internal ratios for second and fourth gear better match new engine power

delivery

• New

50-tooth rear sprocket helps capitalize on the engine’s torque delivery

• Strong,

beefy crankcases feature additional material around the engine mounts to

help increase long-term durability

• Clutch

cable holder is integrated with the crankcase for accurate feel at the

clutch lever

• Scavenge

oil filter screen can be accessed without splitting the crankcases,

facilitating easier maintenance

Quick-turning Chassis

• Utilizes a low-rigidity steering stem for lighter handling

• The

KX250F’s slim and lightweight aluminum perimeter frame is composed of

forged, extruded and cast parts

• Center of

gravity and key dimensions such as swingarm pivot, output sprocket and

rear axle locations designed to increase forward drive with minimal

rear-end squat

• Upper

engine mounts on head cover sides increase overall rigidity

Race-oriented Suspension

• Revised race-oriented suspension damping settings optimize

front/rear balance

• New

Separate Function Fork (SFF) separates springing and damping functions

for less weight, better performance, less friction and easier

adjustability

• Fork now

allows external spring preload adjustability

• Super-hard

titanium coating on the outer surface of the inner fork tubes reduces

friction and improves suspension action. The increased surface hardness

also helps prevent scratches and tube damage


Friction-reducing Kashima Coat treatment on the inside of the outer fork

tubes contributes to smoother suspension action

• Wrap-around

fork tube guards provide greater protection for the inner tubes

• Revised

shock damping settings offer increased absorption performance and

greater stability on corner entry thanks to reduced rear-end kicking

• Features

Kashima Coat on the inside of the shock reservoir for reduced friction

and smoother suspension action

• Rear shock

features dual compression adjustability, allowing high-speed and

low-speed damping to be tuned separately

Superior Rear-wheel Traction

• Swingarm features optimum internal bracing and flex

characteristics for improved cornering performance

• Alloy

swingarm uses a cast front section, tapered hydroformed spars and forged

chain adjusters

• Uni-Trak®

rear suspension system mounts the suspension arm below the swingarm,

allowing more rear suspension stroke and precise tuning

• Linkage

ratios for the Uni-Trak rear suspension match rear shock damping

settings to achieve maximum rear wheel traction

Rider Interface

• Bodywork components offer the rider a slim interface, making

it easy for racers to feel comfortable and go fast

• Formed

using a double-injection molding process, the two-tone shrouds offer a

slim design

• Side number

plates also two-toned and contribute to the slim package

• Right side

panel has an added passageway to help cool the silencer

• Frame is

wider at the ankles to offer better grip and narrows near the bend below

the seat to allow a slim riding position

• Slim seat

features firm urethane, which keeps its original shape longer

• Seat has a

slip-resistant top and side surface for good grip when seated and while

standing

• 50mm wide

(front-to-rear) footpegs offer superb grip and feel at the pegs

• Clutch

cable boot features a large quick adjuster, making it easy for riders to

adjust play in the clutch cable while 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

Factory-style Components

• Black alumite-coated rims, just like the factory racers

• Lightweight

rims offer maximum strength and weight savings

• Thick and

rigid front fender

• Rear brake

pad material offers powerful braking performance

• Front and

rear petal brake discs help reduce unsprung weight, and the wave shape

helps clean the brake pads for more efficient braking performance

• Rear

caliper guard protects caliper from damage

• Ribless

rear hub and butted spokes further reduce unsprung weight

• Renthal

aluminum handlebar is standard equipment


Factory-style graphics complement the KX250F’s highly tuned performance

Additional Features

• Large front brake lever boot offers increased protection

against debris

• Newly

designed and more durable chain guide utilizes a thicker wear pad for

longer life

• Large resin

skid plate offers great protection with minimum weight

Optional Accessories

• Optional DFI Calibration Kit allows custom tuning

• Optional FI

Indicator Light allows the DFI system to communicate diagnostic

information

• Engine

parts include magneto rotors with different inertias and a 12-tooth

output sprocket

• Optional

chassis parts include handlebar holder for a 1 1/8-inch handlebar, 46

• to 50-tooth aluminum

and steel rear sprockets, solid petal brake rotors, different fork and

shock springs and manual decompression lever and cable