2005 Yamaha GP800R Service and Repair Manual
The last GP800R model year is coded GP800AD. Its service coverage closes out the same book that opened the run, LIT-18616-02-26, which Yamaha wrote across 2001 to 2005.
Because the publication spans five years, differences between them are called out in the text rather than left to the reader, and that is the practical reason to know your code before turning a bolt.
The manual takes the craft apart system by system with factory illustrations, gives the measurement limits that decide whether a part is reused or replaced, and lists torque for each fastener group. Electrical faults are worked through with meter readings against stated values, and the harness diagrams are complete. For routine ownership, the periodic maintenance chapter sets the intervals Yamaha expects.