I may have missed something in
my reading of the above but from what I understand you have an electric fuel pump in the tank and fuel making it's way into the first two cylinders. Assuming that is correct I would start by checking the fuel pump pressure. If it is too high it will override the float & overfill the carb bowl causing fuel to run into the intakes. This can also happen if the fuel pump does not shut down as soon as the ignition is turned off. Could also be a bad carb bottom jet seal. This would also cause fuel bowl draining and excessive gas in the cylinders while turned off. The gas could leak past the valves into the cylinder then past the rings into the oil.
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