2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 140Get this manual
CAMSHAFT, ROCKER ARMS AND VALVES 2.Remove: Valve cotters
NOTE: Attach valve spring compressor between the valve spring retainer and the cylinder head to remove the valve cottersValve spring compressor: PNYM-04019, 90890-04019 CAMSHAFT INSPECTION 1.Inspect: Cam lobes Pittingscratchesblue discoloration Replace2.Measure: Cam lobes length and bOut of specification ReplaceCamshaft lobe limit: Intake: 40.52 mm (1.595 in) 32.08 mm (1.263 in) Exhaust: 40.52 mm (1.595 in) 32.08 mm (1.263 in)