Originally Posted by BuRPsa
that's wrong, you need to pipe the bottom-outlet to the rad's, and the top one (connected in your pic) is indeed the overflow, just let it leak if it wants to. Plug the one outlet just under the cap.
C'mon, man. Give me a little more credit than that. Everything is plumbed together and functioning fine. That little tab you see at the bottom of the tank isn't a hose fitting. It's a solid piece of extrusion. I assume it fits into something on the Yamaha it came from to add some stability. The hose at the top goes in, through the rubber cap, and to the bottom of the tank. This allows for the siphoning action that brings the coolant to and from the radiators. The tank's overflow is just to the left of the rubber cap. There is a hose on it now, routed down towards the bottom of the bike.