I just bought a 2003 Kawasaki Vulcan 800 Classic. AKA VN800-B. And I am kind of confused by the switch for the reserve tank. it is written on the top of it, Res. on the right side it is written PRI. And on the bottom it is written ON. What means what and which way do i need to keep it so that I will have my reserve fuel if I need it?