2007-2009 Honda TRX300EX TRX300X service manual, Page 127Get this manual
CYLINDER HEADVALVE
VALVE SEAT INSPECTIONREFACING
Clean he intake and exhaust valves thoroughly to remove carbon depositsApp ly light coat of Prussian Blue to each valve seatTap the valve against the valve seat several imes without rotating the valve, to check for prope valve seat contactHAND-LAPPING TOOL
The valve cannot be groundIf the valve face is burned or badly worn or if ir contacts the seat unevenly, replace the valve
Remove the valve and inspect the valve seat faceThe valve seat contact should be wi hin the speci fi ed idth and even all around he circumf ere nce