This document provides comprehensive information for the 400 All-Terrain Vehicle, covering production years from 1985 through 1995. Known for its robust construction and reliable powerplant, the 400 was engineered for capable off-road performance, serving recreational riders, farmers, and hunters. Its design emphasizes utility and durability, making it a competent machine for various tasks and terrains, reflecting growing expertise in the powersports market during this period. This workshop service manual is designed for mechanics and advanced DIY enthusiasts, offering detailed guidance in English. It covers all essential aspects of the 400, including complete engine overhaul, drivetrain maintenance, suspension and brake system servicing, electrical diagnostics, and fuel system repairs. The manual provides step-by-step instructions for maintenance, adjustments, troubleshooting, and full system overhauls, along with critical technical specifications such as torque values and fluid types, ensuring proper upkeep and repair of the vehicle.