I have an Stihl FS85 that has given me excellent service over the five years of use. It is my only trimmer, and gets used about 2-3 hours per day. The past few day, it has been stopping if I leave it idling for about 30 seconds. It usually happens as I walk between certain parts of the yard, such as end-to-end on a driveway, or other movements between trimming tasks. I carry it with one hand, and after idling for a short time (30 seconds or so), then it will stop. It will tend to slow and sputter in the last few seconds, before stopping. Sometimes getting it started is a challenge. I have noticed the primer bulb does not have fuel. I usually need to push the primer bulb a few times to get it started again, along with some choke. If I stop the engine right after use, wait for 30 seconds, and attempt to restart, it fires right away. In other words, rather than keeping it running (at least my intention) while walking from one area to another, if I STOP the engine, and then refire when ready for use, it starts right away. When running at WOT and working, it runs fine. It does not appear to be short of power. Believing it was getting fuel starved, I thought perhaps the pick-up body inside the tank, with the filter, was partially clogged. I bought a new one today and installed, but I found no change in behavior. I am unsure how the fuel is pumped (pressured, sucked???) from the tank. Is it possible that when running at WOT, the method to get fuel from the tank to the carb is working well, but when running at idle, there is not enough "power?" to get the fuel from the tank to the carb? It has all the marks of this pattern. I have never rebuilt a carb off a 2 cycle like this one, so am unfamiliar with the innards. Is there a diaphragm inside that works to get the supply of fuel to the carb? Perhaps it is failing ....? Anybody have any suggestions (other than "go buy a new trimmer"), or observations I could use to solve this problem?