Fuel will absolutely flow into the exhaust port of a two stroke engine if the piston is below the port. Also, if the piston is high, and the piston skirt doesn't completely cover the exhaust port, then fuel can run in underneath the piston, into the crankcase. Either way you can get a flooded engine and hydrolock. As said before, this most often happens on two strokes that are mounted upright. I have a kadet with a .52 evo on it that will flood and hydrolock everytime I over-fill it, if I wait for fuel to come out of the muffler.