Tuned to suit the demands of race-experienced riders, the 249 cm3 liquid-cooled, 4-stroke Single’s wide powerband focuses on high-rpm performance and extends rideability way into the over-rev. Already highly acclaimed for its high output and power delivery - thanks to race-inspired tuning and factory style parts like the high-performance piston with bridged-box bottom - the 2012 KX250F takes MX engine performance to the next level with the world’s first moto cross dual injection system. The power increase – recognisable by riders of any level – is complemented by inheriting the smooth FI response feel of the 2011 model. Further engine changes offer even smoother shifting and increased durability.

The KX250F fuel injection system features dual injectors: an injector downstream of the throttle valve (where injectors are usually located on standard FI systems), and an upstream second injector close to the airbox. Unlike the dual injection set ups found on supersport models (where the upper injector operates only part-time, providing additional fuel when necessary), the two injectors in the KX250F fuel injection system have different roles. The downstream injector is used to ensure smooth, instant response while the upstream injector is charged with providing power. As rpm and the throttle position increase, operation switches from the downstream injector to the upstream injector. (Depending on whether in a low (1st, 2nd) or high (3rd, 4th, 5th) gear, the switch is either progressive or almost instantaneous.)

A high-performance piston features the same design used on our factory racers, contributing to improved performance at all rpm. A short skirt, reinforced external ribs and the industry’s only mass-production use of a bridged-box bottom, (featuring fully flush internal bracing) result in a lighter, stronger piston.

The KX FI Calibration Kit is the same style kit as used by Kawasaki’s works teams in Europe and the U.S. The kit enables expert riders to adjust engine characteristics (by rewriting actual data maps) to suit their preference, record riding data, and analyse their riding data to further fine-tune their race and practice settings.

The KX250F’s slim aluminium perimeter frame is a lightweight construction created from forged, extruded and cast parts. Chassis balance and settings have all been set to suit race-experienced riders.

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

Stiffer rear shock spring (k=51 N/mm >> k=53 N/mm) and revised shock damping settings (revised piston rod end and revised plug bolt result in narrower oil passageways) result in smooth, steady shock action that offers a firmer feel and increased setting flexibility. The rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately. The rear shock also features the Kashima Coat on the tank cylinder. The reduced friction smoothes suspension action.

On European models, pinched cut-outs in the silencer chambers direct exhaust gases into the glass-wool packing, helping to reduce exhaust noise. The revised silencer internals ensure that strict 2m-max noise regulations are met (115 dB).

A 43 mm throttle body makes use of a progressive throttle link to deliver airflow in much the same way as would an FCR carburettor. Using two linked shafts, the throttle body opens more quickly after the 3/8 open position, delivering sharp response and excellent power feeling. The lightweight throttle body is approximately half the weight of an FCR carburettor – a weight saving of about 600 g.

The KX250F is the only mass-production motocrosser to feature Showa’s Separate Function front Fork (SFF), which separates damping and shock absorption duties: * Left fork tube: damping assembly * Right fork tube: spring The configuration offers both smooth action and firm damping performance – a combination difficult to achieve with a conventional fork.