Probably the higher detergency of the modern oils, the ones that get the ratings a lot of saws are calling for now would help. I do see sparks off the chain when it starts to get dark but don't recall anything coming out with the exhaust. I do have screens but there seems written material on the saw indicating more stuff may be needed.On a serious note (if that is possible): if the sparks are the result of carbon in the combustion chamber, would a richer oil-to fuel mix increase this, or only a richer fuel-to-air ratio? Which would cause more carbon?
Philbert