The Big Bear 400, model code YFM400, is an All-Terrain Vehicle (ATV) designed for utility and rugged off-road performance. Produced for the model years 2000 through 2003, this ATV is powered by a 386cc air-cooled, 4-stroke engine, delivering approximately 21 horsepower and 23.3 lb-ft of torque, coupled with an automatic YCCT transmission. Known for its reliable engineering and capability, the Big Bear 400 features hydraulic disc brakes for effective stopping power and offers both 2WD and 4WD selectable drive systems. Its robust design includes a durable chassis and suspension, making it suitable for a variety of demanding tasks and terrains. This comprehensive workshop repair service manual provides complete coverage for the Big Bear 400, encompassing repair, service, maintenance, restoration, rebuilding, and diagnostics for both 2WD and 4x4 models. The manual details procedures for all major systems, including the engine, fuel system, ignition, cooling, transmission, drivetrain, suspension, steering, braking, and electrical systems. It also covers routine and scheduled maintenance, in-depth troubleshooting guides, and technical specifications such as torque values and fluid capacities. Illustrated with clear diagrams and step-by-step instructions, this manual is an essential resource for DIY owners, home mechanics, and professional technicians seeking to maintain and repair their vehicle.