Small Engines (Lawn Mowers, etc.): 12.5 HP B+S motor stalling after 45 seconds, safety switch, lawn tractor

Question
I have a MTD riding lawn tractor with a 12.5 HP B&S engine.  When the engine is cold, it starts right up and will run for about 30-45 seconds and then immediatly shuts off.  No sputtering.  It's as if the key was turned off.  Then the engine won't start up again for about an hour or more.  It will still turn over, just not start.  After a few hours, I try again, it starts up and then again, it will shut off after 30-45 seconds.  What gives?

Answer
 Hello John:

 Start the Engine. When it Shuts Off, Check for Fire at the Plug THEN. If No Fire, Disconnect the Shutoff Wire from the Coil and Check for Fire, If No Fire, the the Coil/Ignitor/Ignition Module is Bad. If Fire, then Hook the Coil Lead Back to the Plug and Try to Restart the Engine. If it Starts, then a Safety Switch is Bad or the Ignition Switch is Bad or there is a Short in the Harness. If Fire and the Engine Will Not Start, The Ensure you have Free Gas Flow to the Carburetor. If the Gas is Free Flowing to the Carburetor, then Clean and Rebuild the Carburetor. Soak the Carburetor Overnight in Gunk Carburetor Cleaner and Blow Out the Passages with Compressed Air. Install New Kit. Hope this helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John