Kohler COMMAND PRO CS10, Service Manual

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10.8
Section 10
Internal Components
Leakage: A poor grind on face or seat of valve will
allow leakage resulting in a burned valve on one side
only. Gum: Gum deposits usually result from using stale
gasoline. Gum is a prevalent cause of valve sticking.
The cure us to ream the valve guides and clean or
replace the valves, depending on their condition.
Stem Corrosion: Moisture in the fuel, or condensation
are the most common causes of valve stem corrosion.
Condensation occurs from improper preservation
during storage and when engine is repeatedly stopped
before it has a chance to reach normal operating
temperatures. Replace corroded valves.
Coking: Coking is normal on intake valves and is not
harmful. If the seat is good, the valve could be reused
after cleaning.
Excessive Combustion Temperatures: The white
deposits seen here indicate very high combustion
temperatures, usually due to a lean fuel mixture.