2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 215Get this manual
CYLINDER HEADVALVE
VALVE SEAT INSPECTIONREFACING
Clean the intake and exhaust valves thoroughly to remove carbon depositsApply light coat 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: IN: 1.11.3 mm (0.0430.051 in) EX: 1.31.5 mm (0.0510.059 in) SERVICE LIMIT: INEX: 2.0 mm (0.08 in) If the seat width is not within specification, reface the valve seat