So my 1987 TRX350 smokes like a freight train and i noticed it only does it when its hot, so i was wondering if the muffler could have a buildup of oil residue that could cause it to smoke, since it smoked when we bought it, and had smoked for years before that the owner said, it dont smoke running it straight from the header pipe, so this is what leads me to believe its oil residue burning off.