You should get in the habit of switching the tap off when bike isnt in use, all taps were like this before manufacturers saw the light, it only takes a leaking float needle in your carb(s) with the the tap ON to potentially have petrol running into your engine, this petrol can seep down past the piston(s) into the crank case or sit on top of a well sealed piston, either way it could be very interesting when you press that starter button!!!