This manual covers the Suzuki GSXR400 / GSX-R400 (also known as the GSX-R 400) lightweight sportbike, produced from 1984 to 1987. As the first generation of the iconic GSX-R lineage, these models, with chassis codes GK71A and GK73A, established Suzuki's reputation for performance-oriented motorcycles. They are characterized by their lightweight aluminum twin-spar frame, high-revving inline-four engines, advanced suspension for their era, and aggressive styling, making them a significant entry in the supersport category. The GSX-R400 offered a compelling blend of track-capable performance and accessible handling, positioning it as a strong competitor against models from Honda, Yamaha, and Kawasaki. This comprehensive workshop service repair manual, presented in English, is designed to guide owners, mechanics, and technicians through the maintenance, repair, and troubleshooting of the Suzuki GSXR400 / GSX-R400. It provides detailed instructions for all major systems, including engine mechanicals, electrical components, fuel and ignition systems, suspension, brakes, clutch, and transmission. The manual covers routine maintenance procedures, in-depth diagnostic steps, and complete overhaul instructions, ensuring the longevity and optimal performance of the vehicle. Its extensive coverage empowers users with the knowledge to perform everything from basic servicing to complex repairs, saving time and cost while maintaining the integrity of this classic sportbike.