Kawasaki KX250 Service Manual (2005-2008)

Kawasaki established its KX250 as a dedicated 250 cc motocross machine during the 1970s, then developed it through successive generations of two-stroke racing technology. By the 1980s, the model had gained liquid cooling and the Kawasaki Integrated Power-valve System (KIPS), which varied exhaust-port timing to improve power across a wider engine-speed range. During the 1990s, the bike evolved with perimeter-style steel frames, progressively more sophisticated long-travel suspension and increasingly powerful carbureted engines. Its five-speed transmission, close-fitting ergonomics and strong acceleration remained central to its racing identity. The early 2000s brought intense competition from rival 250 cc two-strokes and newly emerging four-stroke motocross machinery, prompting Kawasaki to reconsider the design rather than rely solely on incremental updates.

The redesigned 2005 KX250, designated R1, marked a significant break with the previous 2003–2004 M-series. Kawasaki introduced a narrower, lighter steel perimeter-style frame with steering rake reduced from 27 to 26 degrees, revised rider ergonomics and new rear Uni-Trak linkage geometry. The liquid-cooled 249 cc engine retained its piston-reed two-stroke layout but received redesigned transfer and coolant passages and a substantially revised KIPS exhaust-valve mechanism with independently acting components. Kawasaki also fitted an air/oil-separate inverted Kayaba front fork intended to deliver more consistent damping on hard motocross tracks. Contemporary coverage in Powersports Business's 2005 model announcement and Dirt Rider's first look at the 2005 KX250 identifies the engine, chassis and suspension redesign.

For 2006, the KX250R6F received refinements rather than another wholesale redesign. Kawasaki updated the water-pump impeller, revised the piston profile and engine components, changed the primary-drive arrangement and adjusted the intake and exhaust systems. Suspension tuning also evolved: the Kayaba air/oil-separate fork used a revised internal sleeve for improved bottoming resistance, while the rear shock added high-speed compression-damping adjustment. The model gained Renthal aluminum handlebars, lighter petal-shaped brake discs and revised silencer construction to address noise. The result retained the lively character of the 2005 engine while improving the motorcycle's operation over rough ground and during repeated jumps. The 2006 Dirt Rider evaluation describes the important suspension and reliability changes and distinguishes them from cosmetic updates.

In 2007 Kawasaki retained the same basic R-series engine and frame architecture, with only limited revisions to the two-stroke race bike compared with the previous year. Contemporary testing observed that the 2007 engine was effectively carried over from 2006; the model continued to rely on its 249 cc carbureted single, five-speed gearbox, cable-operated wet clutch and traditional steel frame. The motorcycle's responsive, high-revving power delivery still appealed to experienced racers, although a fast-moving market increasingly favored four-stroke alternatives. Motocross Action's retrospective 2007 test records the minimal year-on-year changes and describes the machine's distinct engine character. The 2007 KX250R7F was among the last 250 cc two-stroke KX motorcycles sold in the United States.

The factory's 2008 KX250R8F designation documents the continuation of this final 250 cc two-stroke motocross generation in markets where the motorcycle remained offered after its U.S. withdrawal. The R1, R6F, R7F and R8F versions therefore represent a compact, coherent period in the KX250's history from the major 2005 redesign to the final regional model-year listings. Unlike Kawasaki's KX250F, which used an entirely different four-stroke engine, these machines retained a carbureted two-stroke racing layout, premixed fuel, kickstarting and a high-maintenance competition specification. Their lasting appeal lies in their light feel, immediate response and the mechanical simplicity of a single-cylinder two-stroke. The shift toward four-stroke competition machinery eventually ended Kawasaki's long-running KX250 two-stroke production family. Other Kawasaki motocross publications can be found in the Kawasaki service manual catalog.