This manual covers the Yamaha WR400F and WR426F models from the 2002 model year. These off-road motorcycles are engineered for high-performance competition and recreational trail riding, featuring a liquid-cooled, four-stroke, DOHC, single-cylinder engine that delivers robust power. The WR400F, with its 397cc displacement, and the WR426F, with its 426cc displacement, are built with torquey power delivery, durable suspension, and capable handling, reflecting Yamaha's rich motorsports legacy and commitment to quality in the off-road segment.

This comprehensive Service and Repair Manual provides detailed information essential for maintaining and repairing your Yamaha WR400F or WR426F. It covers a wide range of systems, including engine mechanicals, fuel and ignition systems, cooling, transmission, suspension, brakes, and the electrical system. With step-by-step procedures for routine maintenance, engine rebuilds, suspension service, and troubleshooting, this manual is an invaluable resource for owners, mechanics, and technicians seeking to ensure optimal performance and longevity of their motorcycle.