Kohler XT-6 Service Manual page 28

Electrical System
Carbon Fouled
Soft, sooty, black deposits indicate incomplete
combustion caused by a restricted air cleaner, over rich
carburetion, weak ignition, or poor compression.
Overheated
Chalky, white deposits indicate very high combustion
temperatures. This condition is usually accompanied
by excessive gap erosion. Lean carburetor settings,
an intake air leak, or incorrect spark timing are normal
causes for high combustion temperatures.
28 KohlerEngines.com 14 690 01 Rev. G