So as the title says, sparks from Muffler not a lot just a few here and there. Dolmar 7900, stock 32" bar working on big sugar maple. Run fuel mix at about 3 oz. to gallon, Just carbon build up or indicative of some other pending problem? Saw is about 8 years old and gets a fair amount of use as I cut split stack about 10 cords a year. I also wanted to increase the oil flow to the chain but I do not seem to be able to turn the adjustment which is a plastic screw with a spring behind it. Feels like the spring has bit into the plastic refusing to allow adj. I am not familiar with major tearing down of chainsaws.