This collection of service repair manuals covers the Yamaha YZ400F and YZ426F models, produced between 1998 and 2002. These motorcycles represented a significant advancement in motocross and off-road competition, pioneering the shift towards four-stroke performance and offering a potent blend of power and handling. The YZ400F, a revolutionary machine, introduced groundbreaking four-stroke technology to professional racing, while the subsequent YZ426F further refined this platform with increased displacement and enhanced performance. Both models are renowned for their robust engineering, competitive edge, and Yamaha's established heritage in off-road motorsport.

This manual provides comprehensive guidance for the maintenance, repair, and troubleshooting of your Yamaha YZ400F or YZ426F. It details procedures for all major systems, including the engine, transmission, chassis, fuel, and electrical systems. Owners, mechanics, and technicians will find step-by-step instructions for routine maintenance, component overhauls, and advanced diagnostics. Technical specifications, torque values, fluid requirements, and troubleshooting flowcharts are included to ensure accurate and efficient servicing, helping to maintain the peak performance and longevity of these championship-winning machines.