Crawdad, take the muffler off Then you can see the exhaust port if there is any carbon build up in there. (Screens on trimmers go in trash before I even start them.)I have never had a problem with any of my saws clogging up, not sure I would want to remove them anyway to much risk of fire with them removed from a saw cutting near lots of dry leaves and wood.) I have 4 an old poulan, 2 husqvarnas a 130 and a 371xp, and a Stihl 017. I only have the troubles with my trimmers. The ones I use now are shindaiwas a t230 and a t270. The screens on both of them were clogged up within a week of use when I bought them. As far as how frequently they need cleaning, mine is about every 3 months of use. I just scrape the carbon out of the exhaust port then they run as good as new. Best trimmers you can buy. The frequency you have to clean them is mostly with the oil to gas mix you use most say to mix 50:1. I run closer to 40:1 in all my equipment. That makes it clog quicker but makes me feel better about engine life. (In my opinion.) Great thread though, Keep them clean and they will run much better with lots more power.