Thanks Rick, but I cleaned the screen when I removed the carb and made sure it was clear with compressed air.  I cleaned the tank of some dirt too.  And, I tried to see if the fuel cap was breathing, but I've never seen one like this before.  Metal tabs hold it in place with a half-turn.  There's no evidence of a pinhole to allow breathing.  I tried to run the engine without the fuel cap to see if it made any difference and it did not matter - it still wanted to slow down and quit.
                 Charlie
                
 January 2007