Unburnt oil will collect inside the pipe. As carbon builds it will hold onto that oil. I took an exhaust from a jog engine, and put it on top of a burn barrel, till the whole thing was cherry red. In the morning the carbon was falling out. I painted it, and put it on my nc/ chopper. It must have weighed 8-10 pounds before, and maybe 6 lbs now. I saw instructions for the oxy burn somewhere, and will try to find it again. Anyway oil is a part of life w/ 2t's "Can't ride it too long or ya smell like a lawn mower" From throw a kit.
