You need to replace the belt, fill it with coolant, then do a pressure test on the cooling system. There is a pump that attaches at the raditor cap for this purpose. If it holds 13 to 15 lb of pressure the coolant system should be okay. One must wonder where the coolant went? Since the belt is missing it would seem it ran hot and lost the coolant. If this is the case I would worry about a warped head and/or cracked block on an aluminum engine.
Hope this helps, if so please accept.
If more information is needed, please ask me.
Hope this helps, an accept would be appreciated.
Firsthogman
Love them Harley's