1999-2004 Honda TRX400EX FourTrax Service Manual, Page 98Get this manual
CYLINDER HEADNALVE
VALVE SEAT INSPECTIONREFACING
INSPECTION
Clean all intake and exhaust valves thoroughly remove carbon depositsApply light coating of Prussian Blue each valve seatTap the valve against the valve seat several times without rotating the valve, check for proper valve seat contact
Remove the valve and inspect the valve seat faceThe valve seat contact should be within the specified width and even all around the circumference
STANDARD: 1.0 1.1 mm (0.039 -0.043 in) SERVICE LIMIT 2.0 mm (0.08 in)