1998 Yamaha WR400 Service and Repair Manual

First season of the WR400, and Yamaha documented it in publication LIT-11626-11-24. The machine carries code WR400FK, and coverage is the 1998 model year.

Two decades on, the manual matters most for figures nobody remembers: valve clearances, shim sizes, cam timing marks, service limits for parts that have since worn. All of it is tabulated. The engine chapters give teardown and reassembly in order, the chassis chapters cover fork and shock work, and the electrical section carries full diagrams for tracing an ignition or charging fault on a bike that has been apart before.

Confirm WR400FK on the frame plate. Note that 1999 uses a different publication number despite sharing the same code.

Capacities, recommended lubricants and adjustment ranges appear in the specification pages, which spares you the guesswork that surrounds a model too new for much second-hand knowledge to have accumulated.