I have a featherlite xt260 weedeater that looses power after running a short period. Starting is not a problem and RPM's seem good at initial start up. The problem is that it begins to loose RPM's shortly after I begin trimming grass and will eventually die. I've cleaned the air filter. I have taken the carburetor off and everything looks clean. The gas lines and filter appear to be in good shape also. Any ideas?

Check the spark arrestor in the exhaust system.