The KX250 motorcycle represents the epitome of Kawasaki's two-stroke motocross development, and it arrives for 2005 with major revisions to the engine and chassis, resulting in more power and better handling to help keep KX250 racers at the head of the pack.
Kawasaki engineers began by creating an all-new Kawasaki Integrated Power Valve System (KIPS®) for the liquid-cooled 249cc two-stroke engine. Previously, the main and sub valves operated simultaneously, causing a power surge after a slight gap in the 6,000 to 7,000 rpm range. By having the valves operate independently, the sub valves begin to open only after the main valve is fully open. Power comes on more smoothly, resulting in a more linear powerband, improved traction and overall more tractable power characteristics. Plus, the cylinder's forward mounting angle has been reduced from 10 degrees to five degrees, which allows for the use of a longer exhaust port, further enhancing power across the rev range.
The engine's coolant passageways within the cylinder are also redesigned for improved cooling, particularly around the exhaust port, to prevent heat-induced power fade during long motos.