Simple really ,oil flows downhill.....leaks from tank into engine ,from engine into primary.....You re pretty lucky its not all over the floor.......My brother came back from holidays to find oil running out under his garage door,and down the driveway,from bikes that had "never leaked before"......Nortons leak down like this in a week,and sometimes fill the engine overnight.......By the way ,drain the engine before starting ,if you decide to start and pump the oil back ,the exhaust will be flooded ,and smoke for 100 miles.
