2005-2008 Honda ATV TRX500FA/FGA Fourtrax, Rubicon Factory Service Manual, Page 175Get this manual
CYLINDER HEADVALVECAMSHAFT
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
The valve cannot be groundIf the valve face is burned or badly worn or if it contacts the seat unevenly, replace the valve
Remove the valve and inspect the 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)