if it only backfires when shutting off, usually this means its getting to much gas!! if it backfires will running adjust carburater.
Backfiring.
Rev the engine six or seven times before coming to a complete stop. Rev it all the way to the edge every time you stop.
Kohler for sure
More than likely you have a exhaust leak.Check the headpipe seal
NO, but a good tuneup will probably cure your problems. There is no cure in a can for the symptoms you list.
If it is backfiring only when you kill the engine, allow the engine to idle a few minutes before you kill it. If it is backfiring while in use, check the intake gasket and bolts for wear or looseness.
The best answer for this is: Get a tune-up.
backfiring.
Hattiesburg, Miss. is the US factory for Kohler engines.
If it is backfiring the timing is set incorrectly or the spark plug wires are not connected in the correct order.
Backfiring is caused by incorrect timing, or plug wires installed incorrectly which messes up the firing order. Make sure your plug wires are installed correctly. Can also be caused by an overly rich fuel air mixture.