If you are totally confident that the carb and all the jets are clean - then that will rule out fuel starvation and all that is left is a rogue ignition part.
Whilst they usually fail and stay failed - you might have a dodgy coil or electronic ignition part that gets antsy when it gets warm / hot and recovers once cold.
BUT before I ran off and bought new ignition parts
- I would just make sure that fuel is flowing properly and freely thru the tank to carb line and that the carb is absolutely clean - If so - then the new ignition parts would be my next step
A test you might try is to start the engine and as soon as it quits - take the plug out and check if you still have a good spark - if not, that should confirm that the ignition is shot
. Wait till the thing cools down - test the ignition again - if you now have spark - you can be pretty sure that you need new ignition / magneto parts