I have a hose that is attached to the top of the crank case right underneath the carburetor which just hangs down and goes to no where? is this some type of an overflow hose or vent or has someone left this disconnected? Thanks!    

My 200cc liquid cooled chinese atv has the same hose running from the top of the crankcase and hangs to the rear of the atv.  must be some kind of vent hose.  In fact the rear axle on this this thing has the same hose that comes out the top and hangs forward, another vent tube probably.