The XS400, produced from 1977 to 1982, represents a significant entry in the mid-size parallel-twin motorcycle market. This first-generation model, encompassing variants like the XS400-1 and XS400-2, is characterized by its air-cooled, four-stroke, DOHC parallel-twin engine, typically displacing around 392 cc. Known for its balance of performance and usability, the XS400 was designed to offer an accessible riding experience, complemented by its reliable engineering and the esteemed heritage of its manufacturer. Its design typically features dual front disc brakes on later models and an enclosed chain drive, contributing to its practical appeal for both commuting and recreational riding. This comprehensive Service Repair Workshop Manual provides essential information for the maintenance and repair of the XS400 models from 1977 through 1982. It covers a wide array of systems, including detailed procedures for engine overhaul, carburetor tuning, transmission, fuel system, electrical systems, brakes, suspension, and bodywork. The manual facilitates routine maintenance, periodic checks, and complex troubleshooting, offering systematic diagnostic procedures and clear instructions for component rebuilds and adjustments. With detailed diagrams, illustrations, exploded views, and complete electrical wiring diagrams, this English-language manual is an indispensable resource for XS400 owners, independent repair shops, and DIY enthusiasts seeking to maintain their motorcycles effectively and economically.