1999-2002 TRX400EX Fourtrax Service Manual, Page 98Get this manual
CYLINDER HEADVALVE
VALVE SEAT INSPECTIONREFACING
INSPECTION
Clean all intake and exhaust valves thoroughly to remove carbon depositsApply light coating of Prussian Blue to each valve seatTap the valve against the valve seat several times without rotating the valve, to check for proper valve seat contact
Remove the valve and inspectthe valve seat faceThe valve seat contact should be within the specified width and even all around the circumferenceSTANDARD: 1.0 -1.1 mm (0.039-0.043 in) SERVICE LIMIT 2.0 mm (0.08 inl If the valve seat width is not within specification, refacethe valve seat (page 7-14)