Small Engines (Lawn Mowers, etc.): Craftsman 6.0 Push Mower, push mower, carburator

Question
My mower is 4-5 yrs old. Starts fine with 5 pushes of the primer. Runs for 20-30 minutes then quits. After 1-2 minutes I can start again (no Prime)runs for 5 minutes then quits. New plug, semi-clean air filter, fresh gas and clean oil. Suggestions?  

Answer
 Hello Noel:

 Do a Test for me, Please. Operate the Mower Until it Quits Again. Now Using Gloves, Remove the Spark Plug and Check to see if it is Firing. If the Plug is Firing, then Check the Gas Cap and Ensure it is Venting the Tank Properly. If the Cap is Good, then Check for Trash/Water in the Carburator or the Filter Needing to be Replaced. If there is No Fire, then the Ignition Module/Coil is Bad. It is Heating up and Shorting to Ground. This Stops the Plug from Firing. When it Cools Enough it will Lose Ground and the Plug will Fire until the Ignition Module/Coil Heats up Again. Hope this Helps. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John