Small Engines (Lawn Mowers, etc.): lawnmower engine, murray lawnmower, valve clearances

Question
my 10-year old Murray lawnmower didn't do so well when I pulled it out of the garage last week for the first mowing of the spring.   I checked the air filter and it looked much better than I had expected, so I did not replace.  but to the problem:  the mower starts fine, but dies out every 2-4 minutes.   if I reprime the engine, it will start back up - run for another 2-4 minutes, then die again.  repeating this process until my lawn was completely mowed was a drag -- HELP!!

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.