Small Engines (Lawn Mowers, etc.): kohler, combustion chamber, carbon buildup

Question
I have a kohler eng. model #CV490S ,after running it for awhile.When I turn off the engine it knocks..Hope you can tell me why... thanks

Answer
Marty

Problem: Engine knocks.
Possible causes:

Magneto is not timed properly.
Carburetor is set too lean.
Engine has overheated.
Carbon buildup in combustion chamber.
Flywheel is loose.
Connecting rod is loose or worn.
Cylinder is excessively worn