Small Engines (Lawn Mowers, etc.): Lawnmower Shuts Down, fuel cap, fuel system

Question
My Yard Machine mower has a B/S  model 42A707,type 2238EI, code 9708215B.
 It runs great!!  But only for about 20 minutes, then it shuts down (it just flames out -KAPUT!)and won't restart for hours. It'll crank like crazy, but it just won't start. I don't have to do anything but let it sit about 5 hrs. approx. and then it starts up like nothing is wrong????????What do ya think?   Thanks,ED

Answer
The first thing I would do is clean the vent in the fuel cap.  Next would be to clean the entire fuel system.  These are the inexpensive trial and error things you can do.  If cleaning the fuel system does not help your problem it sounds as though you may have an intermittent coil this could only be repaired by replacing the coil.