Kohler Courage SV470 Service Manual page 95

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.
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.
Inspection and Reconditioning
Leakage: A poor grind on a valve face or seat will
allow leakage, resulting in a valve burned 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
after cleaning.
Section 9
9
9.7