2001-2006 Honda TRX 300EX Sportrax 300EX Factory Service Manual, Page 117Get this manual
CYLINDER HEADVALVES
VALVE SEAT INSPECTION AND REFACING
INSPECTION
Clean the intake and exhaust valvos thoroughly to remove carbon depositsApply light coating of Prussian Blue to 8ach valv8 faceLap each valve and seat using rubber hose or olher hand-lapping tool
Valves cannol be groundIf the vaillo face is burned or badly worn or if it contacts the seat unevenlyreplace the valveRemove the valv8 aod inspect the face Uneven seat width: