Small Engines (Lawn Mowers, etc.): starts great but once hot shuts down, briggs and stratton, hp briggs

Question
HI
I have a 16.5 hp briggs and stratton motor twin.
I have changed the plugs, fuel filter, and cleaned the carb (at least i think i have).  The lawn tractor starts fine and will run 10mins to 30 mins then it starts losing power like its not getting any fuel, if i choke it it goes a little longer but with the same final result, it stops.  Does the carb need a better cleaning or replaced, is there a coil or solenoid somewhere that is the culprit.  Any expert advice and direction would be greatly appreciated

thnx
Wayne

Answer
Hi wayne,

I suspect some dirt or clog, still in the carb.  Check the float with it's needle and seat.  But also check the fuel tank cap to be sure it is venting.  Check for spark right after it quits, to eliminate an ignition problem.  

Let me know how you make out.
Michael