Service Manual

25
Valve Seat Reconditioning
1. Thoroughly clean the combustion chamber and valve seats to remove carbon deposits.
2. Apply a light coat of Prussian Blue or erasable felt-tipped marker ink to the valve faces.
3. Properly install valves, springs and keepers. Manually open the valves, then and snap them closed
against their seats several times. Be sure the valves do not rotate on the seat. Remove the valve
assemblies. The transferred marking compound will show any area of the seat that is not concentric.
4. Use a 45°cutter to remove enough material to produce a smooth and concentric seat. Follow the valve
seat cutter manufacture’s instructions. Turn the cutter clockwise, never counterclockwise. Continue to
turn the cutter as you lift it from the valve seat.
5. Use a 30°~32° and 60° cutter to narrow and adjust the valve seat so that it contacts the middle of the
valve face. The 30°~32° cutter removes material from the top edge. The 60° cutter removes material from
the bottom edge. Be sure that the width of the finished valve seat is within specification.
6. Lap valves in accordance with valve lapping kit instructions.
7. Clean valve and seat of all lapping compound.
Valve Seat Width
Standard
Service Limit
0.03149 - 0.0393”
(0.8-1.0 mm)
0.0591”
(1.5 mm)
CONTACT TOO LOW
CONTACT TOO HIGH
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