UPDATE: Kawasaki released details on the new line up of motorcross racing machines

Kawasaki Motorcycles/Dirt Bikes

The mean green machine!

Kawasaki Motorcycles has released details on its 2011 KX250F and KX450F motocross racing machines.

According to the company there are nearly 30 upgrades to the 2011 Kawasaki KX250F, reflecting “the rigour of testing and development happening at Kawasaki”.

Refinements to the 249cc single include higher compression, a modified top on the exclusive Bridged-Box Bottom piston, higher valve lift, longer spark plug design, and a new coil that offers a hotter and longer-lasting spark.

For 2011 the KX250F Dirt Bike also gets Digital Fuel Injection (DFI) which automatically adjusts to suit track and climate conditions.

An optional ECU Setting Tool allows racers to select from several different ECU data maps or fine tune a custom map.

The tool can also record up to six hours of data, including engine r/min, degree of throttle opening, coolant and air temperatures, ignition timing, fuel adjustments, gear position and system voltage.

Headlining the chassis changes on the KX250F is Kawasaki’s new Separate Function Fork. Instead of a conventional fork design, the SFF separates spring and damping duties (one in each leg) for improved performance, less friction, lower weight and easier adjustability.

The right leg has the spring, with a larger main spring/rod assembly than traditional forks; the left leg handles damping, with rebound and compression damping adjustable on the fork tube.

On the KX450F’s front, changes for the 2011 model year are much smaller and includes revised cam timing which results in better mid- and top-end performance as well as a reinforced cylinder sleeve and crankcase which offer improved durability.

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.

Kawasaki has also revised the engine mount brackets to help optimize chassis flex and improve handling on there Dirt Bike. The damping settings for the fork tubes and the rear shock have also been revised to provide lighter handling, improved suspension action, increased comfort.

Features for the KX450F

  • 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

Features for the KX250F

Kawasaki Motorcycles/Dirt Bikes

Blasting on the KX450F

  • 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
  • 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 stiction, 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

Kawasaki’s tagline, “Let the good times roll.™”, is recognized worldwide. The Kawasaki brand has become synonymous with powerful, stylish motorcycles for over four decades. Information about Kawasaki’s complete line of recreational products and Kawasaki affiliates can be found on the Internet at www.kawasaki.com.

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