Mazda Trucks 1972-1986 Repair Guide
REMOVAL & INSTALLATION
With the valve removed, check the seat for wear, cracks, damage or uneven contact with the valve. If the damage or contact problem is slight, the valve may be refaced with a lapping compound and lapping tool. The compound is spread on the seat face and the valve inserted. The valve is then ground against the seat with the lapping tool, removing a small amount of metal and creating a polished surface.
If the damage or contact problem cannot be rectified by lapping, the insert can be cut with a special seat cutter which will remove the damaged material and cut the correct angle.
If the seat insert is cracked, too thin, or burnt, it must be replaced. An automotive machine shop can handle the job for you.