Has all the classic symptoms of a clogged gas tank cap vent.
Find the vent hole in the gas tank cap and probe it clean with a stiff wire (unfolded paper clip). Then, if you have compressed air available, blow out the hole.

I checked the gas tank cap vent and it is not clogged. Used a paper clip as you instructed and blew out the hole, Still stalls out after running for 10-15 minutes.

Possible that the ignition coil is failing, OK when cold then opening up as it heats up. Best way to test is to substitute with known good coil.

when engine stalls, quickly remove carb air cleaner, spray cuppla shots of rattlecan carb cleaner directly down carb throat. Try to start engine. If engine "pops" or catches momentarily, you still have a fuel flow problem. If not, then ignition or mechanical problem.
If ignition problem from just the start of this year, you may have trash or mice nests under engine cooling shroud - removel sheet metal to clean/inspect.