The spark arrestor screen in the muffler may be plugged.

My Stihl was doing something like that and the fuel line was sucking air (dried out).

Dave

If it did this after sitting for a while most likely the carb is gunked up and needs to be cleaned, I wouldn't think the fuel lines would be shot in 2 years, could be. Steve

I also think it's sucking air or carb. passages are dirty. First I would try to richen the mixture (1/16" to no more than 1/8 turn) see if that does anything, Just note where you started so you can turn it back to the orginial spots. IMO if that does nothing I would disassembe the carb and clean the passages noting if any of the mounting screws were loose.

If you take the carb off be carefull when tightening the screws when putting it back on. They screw into plastic and strip easy. Steve