Kohler Command Pro CV960 Service Manual page 98

Section 9
Inspection and Reconditioning
Normal:
can be reconditioned and reused if the face and
margin are in good shape. If a valve is worn to where
the margin is less than 1/32" do not reuse it. The valve
shown was in operation for almost 1000 hours under
controlled test conditions.
Bad Condition: The valve depicted here should be
replaced. Note the warped head; margin damaged
to excessive hours or a combination of poor operating
conditions.
9.6
Leakage: A poor grind on face or seat of valve will
allow leakage resulting in a burned valve on one side
only.
Coking: Coking is normal on intake valves and is not
harmful. If the seat is good, the valve could be reused