I've recently been having problems with my Stihl FS-55 weedeater. First it has been getting harder to start the last couple of months and it is a new plug. Then recently it will start but will not rev, it would just barely idle, and sounded horrible. I'm not that mechanically inclined so I figured it had gotten out of adjustment on the mixture screws. I played with all of them until they were practically stripped out and no luck, followed the manuals proceedures to adjust and everything and I knew it wasn't the air filter because I removed it and it didn't get any better. Well as I said I'm not that mechanically inclined so I was ready to take it to the dealer and have to use my piece of crap backup weedeater, but I figured I would take it to a friend who is very mechanically inclined and seems to know how to fix everything. Well I started it for him and after a couple of seconds it died and he told me that it sounded to him like the exhaust was plugged. My first thought was yea right, its only two years old, but from past experiences with him working on equipment I knew that he was able to fix just about anything so I didn't have a problem with him tearing into it, heck it was going to have to go to the dealer anyway so what did I have to lose. Well the first thing he did was pull out the muffler and then unscrew the exhaust port and wow that son of a gun was plugged solid with carbon. For those of you who dont know there is a mesh screen on the exhaust port for what reason I'm not sure but mine is not there no more. He put her back together and she runs like new, starts the first pull and revs and idles nice. I figure this is why Stihl reccommends that you operate your weedeater at full throttle so this wont happen, because I am the type of person to operate at 50% or less throttle for the majority of the time to cut down on damage to saplings, trees, and to throw less rocks, pebbles and other debris. It should be noted that we took apart a Stihl brushcutter that was older than mine and used much more frequently than mine and checked the exhaust screen and it did not have one speck of carbon on it probably because they are constantly run a full throttle. Hope this saves a couple of you a trip to the dealer.