Small Engines (Lawn Mowers, etc.): edger motor will not stay running, briggs and stratton, valve clearances

Question
MTD edger w/briggs and stratton 3.5hp. about two years old.
Starts okay, but when it gets warmed up it stalls.
choke is not sticking, new plug, new gas, new air filter.
thanx for your time.

Answer
Before you try any repair, I suggest you loosen off the gas cap a little and see if this fixes the problem.  If the tank vent is plugged you will need to replace the fuel cap.  Otherwise, if you have a problem related to heat or time, it can generally be attributed to one of two things.  First you need to make sure you still have spark after it quits.  If you have no spark, the ignition module will need to be replaced.  If you have spark, you will need to listen carefully to engine for a "whisping" sound in the exhaust.  If the valve clearances are insufficient, the valves can hang open when the engine gets hot.  Hope this helps.