Farmer...I don't think your fuel and oil are seperating...that said I always shake a can of mix too...just habit I guess. Anyway here is what ( I believe) is happening. When you last shut your saw off, the crankcase was fully charged with fuel. The cyl and piston was coated with unburnt mix as well from the few revolutions it turn with ign off. Saw is now stopped for a few months and the gasoline evaporates out through the transfers, exhaust and carb depending where the piston stopped. This leaves the entire crankcase, piston and cyl coated with just your lube oil, you pick the saw up pull it 5-6 times (if it starts good) adding enough fuel to the crankcase to fire up on. Well this mix mixes with the left behind oil from before and picks it up and burns it. If you are running 50:1 then for a period of time the saw will actually getting something like 25:1 until it cleans all the old oil from the interior of the motor and it smokes!!