There is a rubber overflow tube (I think thats what it is?) to the left of where the crank case breather hooks into the air intake.It looks like it is supposed to be run through a metal clip and straight down next to the crankcase breather tube and doesn't hook to anything. If you were sitting on the bike it would be to the left of the air intake that is attached to the airbox cover. Is that supposed to hook to anything? So what I'm trying to say is that there is a small tube to the left of the crank case breather tube that doesn't look right cause mine wasn't through the clip and is kind of hangin'there. Its really hard to explain without a picture.

 

www.delphi.com/raptor660/start

Later-Joe

 

Why can't you just look and see where the other end is connected? If you don't see another 1/4" hose somewhere that is unconnected, it has to be the overflow from the carb bowl

 

I think the one hose in question is a vent hose from the starter housing it starts small and ends up larger.

 

I believe you are referring to a carburetor vent line. If you kink it, your quad will die, so I believe that it is there to allow gas to enter your carb bowl and for air to exit.