This manual covers the WR400F, a versatile off-road motorcycle known for its robust engineering and performance capabilities in various terrains. Produced from 2000 through 2008, the WR400F draws from extensive motorsports heritage, offering a reliable platform for enthusiasts and experienced riders alike. Its design prioritizes durability and handling, making it a capable machine for trail riding and enduro competition. This comprehensive workshop service repair manual, written in English, provides in-depth guidance for maintaining and repairing all styles of the WR400F. It details engine and transmission procedures, electrical system diagnosis, chassis components, and bodywork. The manual includes routine maintenance, step-by-step repair instructions, troubleshooting diagnostics, and essential technical specifications, all supported by hundreds of photos and illustrations to ensure clarity and accuracy for DIY enthusiasts and professional mechanics.