Kohler LH630-775 Service Manual page 134

Section 10
Inspection and Reconditioning
Hard starting, or loss of power accompanied by high
fuel consumption may be symptoms of faulty valves.
Although these symptoms could also be attributed to
worn rings, remove and check the valves first. After
removal, clean the valve heads, faces, and stems with
a power wire brush. Then, carefully inspect each
valve for defects such as warped head, excessive
corrosion, or worn stem end. Replace valves found to
be in bad condition. A normal valve and valves in bad
condition are shown in the accompanying
illustrations.
Normal: Even after long hours of operation a valve
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.
Leakage: A poor grind on face or seat of valve will
allow leakage resulting in a burned valve on one side
only.
10.6
Bad Condition: The valve depicted here should be
replaced. Note the warped head; margin damaged
and too narrow. These conditions could be attributed
to excessive hours or a combination of poor operating
conditions.
Gum: Gum deposits usually result from using stale
gasoline. Gum is a prevalent cause of valve sticking.
The cure is to ream the valve guides and clean or
replace the valves, depending on their condition.