This workshop service repair manual provides comprehensive information for the YFZ450R and YFZ450RY models, covering production years from 2004 to 2013, encompassing both the First Generation (2004-2009) and Second Generation (2010-2013). Engineered for performance, the YFZ450R features a robust 4-stroke, liquid-cooled, DOHC, 5-valve, 449cc engine with fuel injection, a constant mesh 5-speed transmission, and electric start, making it a capable machine for recreational riding and competition. Its advanced chassis geometry and reliable components are designed for optimal handling and durability. This manual serves as an essential guide for owners and technicians, offering detailed step-by-step instructions, diagnostic procedures, troubleshooting guides, and clear illustrations and diagrams. It covers all aspects necessary for maintaining and repairing the YFZ450R, including routine service recommendations for oil and coolant, tire pressure specifications, and engine oil capacities. With its extensive coverage and user-friendly format, this English-language manual is an indispensable resource for ensuring the longevity and optimal performance of your vehicle.