New Refinements for the 2011 Kawasaki KX450F
by Jon Crowley on 26/05/10 at 8:31 am
Kawasaki 2011 KX450F
In the 450cc motocross game, the only thing that matters to serious racers is top-tier performance. And for 2011, the best tool for the job is Kawasaki’s reworked KX™450F. The latest open-class KX starts with a brutally fast 449cc DOHC four-stroke single packing a broad spread of power.
Last year’s KX450F featured the first-ever production use of a bridged-box bottom piston, yielding more high-end power. Revised cam timing means better mid- and top-end performance and a reinforced cylinder sleeve and crankcase offer improved durability.
Its lightweight yet strong aluminum frame combines with a suspension designed to offer compliance, high-speed stability and whoop-sucking performance all moto long. New revisions to the engine mount brackets help optimize chassis flex and improve handling. The damping settings for the massive fork tubes and on the rear shock have also been revised, providing lighter handling, improved suspension action, increased comfort and greater cushioning when landing from jumps. The drive chain guide has been beefed up for increased durability; tests show it to be nearly three times more durable than last year’s. Plus, the chain has thin inner links that make it slightly lighter than typical designs.
The KX450F’s Digital Fuel Injection (DFI®) automatically adjusts to suit track and climate conditions, and offers stable fuel metering even when landing from jumps in tough motocross conditions. The ECU provides a hotter and longer-duration spark for improved low-rpm response. The shift mechanism incorporates a larger internal roller and stronger shift-spring tension for more positive shifting. An optional ECU Setting Tool allows racers to select from several different ECU data maps, or fine tune a custom map that alters fuel injection and ignition timing to suit different tracks and conditions. The tool can also record up to six hours of data, including engine rpm, degree of throttle opening, engine boost, coolant and air temperatures, ignition timing, fuel adjustments, gear position and system voltage.
- The massively powerful 449cc single is tuned for a broad powerband with the torque curve set just under the wheelspin threshold
- Digital Fuel Injection self-adjusts for easier starting, sharper throttle response and optimized power and stability when landing from jumps and other high impacts
- Purpose-built ECU has refined settings that offer improved response at low-to-mid rpm; starting can be accomplished in a single kick
- Revised bridged-box bottom piston shape has the same design as used on the factory racers – a short piston skirt with low-friction coating for reduced mechanical losses, reinforced external ribs for durability, and fully flush internal bracing for strength
- Revised race-oriented suspension settings offer maximum overall performance
- Revised engine mount brackets optimize frame rigidity for better handling
- Increased front axle collar diameter transmits more feedback from the contact patch to the rider
- 5-speed transmission and excellent low-rpm engine response combine to offer riders more gear options to suit a wide variety of tracks
- Revised seat uses a slimmer design and firmer urethane foam to keep its original shape longer
- Optional ECU Setting Tool allows racers to select from different data maps or tune their own; tool also records up to six hours of data
A slim seat design with firm urethane foam and a non-slip top and side surface provides even more seated and standing grip while retaining excellent rider mobility. The frame echoes the slip profile at the top, but widens at the lower level by the ankles to provide the rider with better feel and control. Completing the rider interface are wide 50mm footpegs that offer tenacious grip and a comfortable platform.
The race-ready engine is compact and light, with a short, 100mm cylinder head and a 12.5 compression ratio. The bridged-box-bottom piston features a revised shape this year to help improve horsepower, while cam timing was tweaked accordingly to maximize power delivery. All those horses are delivered to the rear wheel via a clutch featuring superb oil drainage and beefy friction plates.
The Kayaba rear shock’s revised damping settings contribute to improved wheel control and impact performance. It features a large 50mm piston and Kashima Coat treatment on the shock internals to help maintain a plush ride. Easily accessible dual compression adjusters allow high- and low-speed damping to be tuned separately, giving mechanics and riders the ability to easily fine-tune the suspension for difficult track conditions.
The fuel-injection system automatically adjusts to suit track and climate conditions, and offers stable fuel metering even when landing from jumps in tough motocross conditions. The DFI system includes a 43mm throttle body, a lightweight aluminum fuel pump and an ultra-fine atomizing injector, which sprays precise, 60-micron fuel particles to help provide smooth power delivery and accurate engine response throughout the rpm range.
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