The Yamaha Raptor 660, model designation YFM660R, is a high-performance All-Terrain Vehicle (ATV) that set a benchmark in its segment. Produced between 2001 and 2005, this sport ATV is powered by a 660 cc single-cylinder, 4-stroke engine, known for its robust performance and liquid-cooled design. Its engineering quality is evident in its advanced features for its time, including a 5-speed transmission with reverse, a wet, multi-disc clutch, and a reliable chain drive system. The Raptor 660 was a pioneering model, building on a strong lineage in sport ATVs and offering exhilarating performance for recreational riders and enthusiasts. This Factory Service Manual (FSM) provides comprehensive technical information for the Yamaha Raptor 660 (YFM660R) models from 2001 through 2005. It covers all essential aspects of the vehicle, including detailed procedures for engine mechanicals, fuel and ignition systems, cooling, transmission, suspension, brakes, and the electrical system. The manual includes routine maintenance schedules, troubleshooting guides for common issues, component replacement instructions, and critical torque specifications. This resource is invaluable for owners, DIY mechanics, and professional repair shops, enabling confident and accurate maintenance, diagnosis, and repair to ensure optimal performance and longevity of the vehicle.