This manual covers the 1985 Suzuki GSX-R400 motorcycle, model code GK71B. As an early entrant in the 400cc sportbike class, this motorcycle is recognized for its performance-oriented engineering, featuring a liquid-cooled, 4-stroke, DOHC, inline-four engine with a displacement of 398cc. Its design emphasized lightweight construction and high-revving capability, reflecting Suzuki's heritage in producing competitive sportbikes. The GSX-R400 is equipped with a responsive braking system, stable chassis geometry, and robust frame construction, contributing to its active and passive safety features. This comprehensive Service Repair Workshop Manual in English provides detailed information for the maintenance, repair, and troubleshooting of the 1985 Suzuki GSX-R400. It covers a wide array of systems and procedures, including general information, assembly and disassembly, routine maintenance, engine and transmission overhauls, fuel and lubrication systems, electrical components, and advanced troubleshooting. The manual is designed to assist professional technicians, experienced DIY mechanics, and enthusiasts by offering step-by-step repair procedures, detailed diagrams, torque specifications, and electrical data, enabling effective upkeep and repair of the vehicle.