YFM400FWR is the 2003 Big Bear 4WD, and its service manual is the one Yamaha numbered LIT-11616-BB-40.
One book for five years
Coverage takes in 2002 through 2006. The model codes change from year to year across that span while much of the service work does not, which is why Yamaha kept them in a single volume and noted the differences where they matter.
Procedures include periodic maintenance, engine removal, disassembly and reassembly with factory measurements, fuel system and carburetor service, clutch and transmission work, final drive and four-wheel-drive components, brake and wheel service, steering and suspension, and the electrical system with wiring diagrams. Tightening torques are given in place, and the troubleshooting chapter follows the factory's own sequence.
