Have a '99 WR. Got cylinder head gasket and cylinder gasket off ebay, ment for YZ 400 '98. Part numbers are: 5GR-11181-00-00 for head 5BF-11351-00-00 for cylinder. But for '99 WR are: 5BE-11181-00-00 for head 5BE-11351-00-00 for cylinder. Visually can't distinguish head gasket diffrences, but with cylinder gasket, there is a thickness diffrence...WR measuring 1.1 mm or 0,043 inch and YZF measuring 0,6 mm or 0,023 inch. What can I expect with thinner gasket..higher comppression or piston hitting valve. Cyl and head codes WR and YZ also differ slightly. Second thing, more like a job well done is fine tuning the head. Reconditioning valve seats and valves and also head surface leveling. Yamaha uses only two angles on the seat, I have now three angles and also angles are diffrent for better flow. Valves are suited, to fit the angle of course. This is 9 years old head, first valves, everything in spec, only valves were a bit leaky, so I was loosing a bit compression and that was probably reason for a bit higher oil drainage from head vent tube and quick oil contamination. Since I also have reconditioned cylinder, presume I'll ride quality now.