OK I am old, engines did not stop because the muffler got dirty. NOW THEY DO. twice this summer once on a gen set and once on a stihl saw they would not run no matter what I tried. Warning, our great leaders in DC are NUTS. Spark arrestors on both caused them not to start or run. After cleaning they do. Heck I couldn't even find the one on the stihl and the nice lady at the gen set co told me where that one was. OH MY!! They might start a fire/heck non of my old ones ever did. WARNED and edgomacated. CK the spark arrestor.