Stihl only idle

[zark]

I dont know if the trimmer has a spark arrestor screen or not. But I had an MS 181 chain saw for brush cutting, etc. It would sit for some periods of time at idle while I stacked, chipped, etc. This would clog the screen every couple days of use. Would idle great and bog when trying to cut, clean the screen and it would run like new. Sure does sound like the problem?

 

[DaveTN]

Usually when I find a weedeater or chainsaw that will idle, but won't throttle up, first thing I do is turn the LOW side counter-clockwise to enrichen it. Turn about 1/16th turn, then check for throttle up. If it improves some then do another 1/16 turn, and repeat until it throttles up OK. Then I go to the HIGH side and hold the throttle about 1/2 to 3/4 open and adjust the HIGH side until the engine revs at its best RPM. Then STOP. If it still stumbles and won't throttle up, I'd take the carburetor cover plates off and check the diaphragms. Spray them out, clean the carburetor with spray etc. and replace them in order removed. That usually does the trick!