Kawasaki KX250F Service Manual (2011–2012)

Kawasaki introduced the KX250F in 2003 as a newly developed four-stroke motocross machine and the first product from Kawasaki and Suzuki's motorcycle-development collaboration. Kawasaki's official launch announcement described a new 249 cc liquid-cooled single-cylinder four-stroke engine, a redesigned perimeter frame and Uni-Trak rear suspension, all developed around motocross competition. That launch established Kawasaki's modern 250 four-stroke race line, which would become an important model in AMA Supercross, motocross and other national racing series.

The 2011–2012 KX250YB/YC generation is a 250 cc four-stroke motocross bike built around a 249 cc liquid-cooled DOHC four-valve single with a 77.0 × 53.6 mm bore and stroke and 13.5:1 compression. Fuel delivery is electronic injection through a 43 mm Keihin throttle body, with kick starting, digital DC-CDI ignition, a wet multi-disc clutch, five-speed constant-mesh transmission and chain final drive. The chassis uses a tubular semi-double-cradle frame, 21-inch front and 19-inch rear wheels, long-travel inverted Showa forks and Uni-Trak rear suspension. Its maintenance schedule is race-hour based, emphasizing the high-service-intensity nature of a competition motocross machine rather than road-bike intervals.

The two years share the same basic KX250Y platform but are not mechanically identical. The 2011 KX250YB uses a conventional single fuel injector, while the 2012 KX250YC introduced a second upstream injector in the intake duct. The factory manual states that the 2012 KX250YC was the first motocross model to adopt dual-injector technology, using the downstream injector alone at low engine speeds and both injectors in the mid-to-high range. Kawasaki's later KX250F technical paper describes the system as a way to combine low-rpm response with stronger high-rpm performance. The manual also records YB/YC-specific differences in curb mass, fork-oil quantities and several service procedures.

The KX250F continued to evolve rapidly after this Y-series generation. Kawasaki's official Owner Center identifies the 2013 successor as the KX250ZDF, marking a model-code transition beyond the YB/YC motorcycles covered here. Across the broader lineage, fuel injection, dual injectors, launch-control technology and continuing chassis development show how Kawasaki progressively transferred factory-racing ideas into its production motocross range rather than treating the KX250F as a static platform.

This download is specifically factory publication 99924-1437-02, whose application table covers 2011 KX250YB and 2012 KX250YC. Because the manual itself documents differences between those two model years, service procedures and specifications should be matched to the correct YB or YC code. Related Kawasaki motocross manuals can be browsed in the KX250F service manual category.