The Yamaha YZF-R1S, produced from 2004 to 2006, represents a pinnacle of supersport motorcycle engineering. Building on a rich motorsport heritage, this model is renowned for its potent 998cc inline-four engine, delivering approximately 172 horsepower, and its advanced Deltabox aluminum frame, which provides exceptional rigidity and precise handling. Designed for performance-oriented riders and track day enthusiasts, the YZF-R1S features a high-revving engine with five valves per cylinder, a sophisticated fuel injection system, and a high-performance braking setup. Its aerodynamic bodywork and focus on power, handling, and braking have earned it consistent recognition in the supersport segment, solidifying its reputation as a formidable machine for both exhilarating road riding and competitive track use. This comprehensive factory service repair manual serves as an essential resource for owners and technicians alike, covering all aspects of the Yamaha YZF-R1S from 2004 to 2006. It provides detailed, step-by-step instructions for routine maintenance, including oil changes, filter replacements, and chain adjustments, as well as in-depth procedures for engine disassembly, assembly, and overhaul. The manual also includes extensive troubleshooting guides for various systems such as the fuel, cooling, electrical, and braking systems, along with advanced diagnostic procedures for electronic components. With clear explanations, diagrams, and technical specifications, this manual empowers users to maintain, diagnose, and repair their YZF-R1S effectively, ensuring optimal performance and longevity.