My Stihl FS 55 weed Wacker started to run bad so without thinking I tried to adjust the carb (slotted screws) and nothing. I tried several times then put it down for the next day. As soon as I got in the house I thought, I should check the spark arrestor. The next day I pulled the spark arrestor, and it is almost completely plugged. I adjusted the carb back to ¾ and 1 full turn pulled the rope, and you will never guess it started running and running real good. Used a torch to clean the arrestor. The moral of the story first spark arrestor then fuel and spark. Don’t ever get old (86) and still cutting grass and trying to do all my repairs, it is getting tougher all the time.
I've picked up quite a few chainsaws and weed eaters over the years for this problem. It's simple to fix, but many overlook the muffler and spark arrestor.
Sad part is, very few people these days want to buy perfectly good and often more reliable older units like this one.