I have just experienced this problem and the results were devastating. The muffler is bad replace it right away or you will be dealing what I am dealing with. The red hot muffler caused the engine to over heat, it blew the oil right out causing a whole engine rebuild! And getting parts for this thing is ridiculously expensive and that's if you can find them. The muffler is expensive I paid $640 for mine. Before you can get it replaced your engine will burn oil bad. Keep a close eye on the oil or you will be in the same boat as me.