Yes the oil can affect it but if you still have a spark arrester screen in your muffler thats where your problem is.If you in a part of the states where you have to have them you can clean the screen by torching it with a "PROPANE" torch and get it glowing red and it will burn off the carbon,DO NOT USE A OXY ACCETALINE TORCH !!! You'll melt it in a flash.
