The KX450F Motocross Motorcycle, produced for the 2009 and 2010 model years, represents a pinnacle of high-performance off-road engineering. This competition-focused machine is renowned for its liquid-cooled, four-stroke, 449cc engine featuring a DOHC, four-valve configuration and an advanced Digital Fuel Injection (DFI) system for optimized power delivery. Key innovations include the Separate Function Front Fork (SFF) suspension, designed to provide superior damping and spring characteristics, and a lightweight aluminum perimeter frame for enhanced agility and stability. The KX450F is engineered for demanding motocross racing environments, catering to both amateur and professional riders seeking a competitive edge. This comprehensive factory service repair manual provides essential information for the maintenance, repair, and troubleshooting of the KX450F models from 2009-2010. It covers a wide array of systems, including detailed engine overhaul procedures, fuel injection and ignition systems, cooling, drivetrain, front and rear suspension, brakes, wheels, tires, steering, and the electrical and frame components. The manual offers guidance on routine maintenance, engine rebuilds, suspension tuning, torque specifications, and includes detailed wiring diagrams. Its thorough scope ensures that owners, technicians, and mechanics have the necessary resources to keep this high-performance motocross motorcycle in optimal condition.