Small Engines (Lawn Mowers, etc.): weed eater, tank fuel, fuel cap

Question
Hi Fred,

I am trying to fix my weed eater it is fairly old and has run well in the past.  The thing is that it will run fine for about 30-40 min (I have a big yard) and then it will just quit.  Sometimes I can run it for another 2-3 minutes but then it quits for good.  I have no idea what the problem might be since it will start up.  Any ideas would be appreciated.

Answer
Wow, 30 to 40min is a lot of trimming.

I would start with the fuel cap vent.  If that is plugged a vacuum would form in the tank.  Next check the in-tank fuel filter, and fuel line.  If the line is nor in good condition replace it.  Next the carburetor remove disassemble it, install a carb kit and replace all gaskets.  Look at the insolation block to see if warped.  This is the block between the carb and the engine.  

Next is how old?  If this is an older trimmer and you purchased an economy brand it may be wore out from all that trimming.