Small Engines (Lawn Mowers, etc.): Engine wont keep running, john deere lawn tractor, john deere lawn

Question
I have an 18 yr.old John Deere lawn tractor with a Kohler 12.5  hp engine. Recently, the engine will start, run for 5-10 minutes, and then suddenly stop and will not restart. I have cleaned spark plug, drained and cleaned gas tank, checked fuel filter, removed and cleaned carburetor. I'm at a loss for a solution.

Answer
Do you have spark when the engine dies?  I'm betting no.  If no replace the coil. If you do have spark you have a carb issue.

I replace about 25 STX coils a year.  

Your mower would be perfect for me.  I'd have to stop every 10 minutes for a beer anyway.

Joking aside, replace the coil.