You´re fine leaving it in the "ON" position. All the "ON" and "Reserve" switches do are change the point in the tank that fuel is taken from, so when you go to "Reserve" it draws lower in the tank. When fueling, the tank will fill either way. How do you like your bike? I am thinking of picking one up, it´s a ´97 with 7400 miles on it. I love my current bike, but I want a sportbike bad