This manual covers the GS250, GS450, GSX250, and GSX400 motorcycle models manufactured between 1979 and 1985. These motorcycles are characterized by their parallel-twin engines, with the GS series featuring SOHC and shaft drive on some variants, and the GSX series equipped with DOHC and chain drive. Throughout their production run, a reputation for engineering quality and reliability was established, making these models popular choices for riders seeking performance and value. The GS and GSX lines were instrumental in growth, offering a range of options from entry-level to more performance-oriented machines. This comprehensive Service Repair Workshop Manual provides detailed, step-by-step instructions for all aspects of maintenance, diagnosis, and repair for your motorcycle. It covers essential systems including the engine, transmission, fuel system, electrical system, brakes, and suspension, offering guidance on everything from routine oil changes and valve adjustments to complete engine overhauls and troubleshooting common issues. With high-quality diagrams and detailed technical data, this manual is an invaluable resource for owners and technicians alike, enabling confident and efficient upkeep of these classic motorcycles.