Do you have that O ring installed on the end of the starting motor? The motor should be a snug fit in the hole, but not have to "forced" in.
Since the nose of the motor is inside the crankcase, any blow-by in the crankcase will take the course of least resistance and try to escape the easiest way. I would think that if all your crankcase vent hoses are attached and not blocked, that there would be minimal pressure on the starting motor seal.
Since the nose of the motor is inside the crankcase, any blow-by in the crankcase will take the course of least resistance and try to escape the easiest way. I would think that if all your crankcase vent hoses are attached and not blocked, that there would be minimal pressure on the starting motor seal.