Carburetor Hose Question

[RodneyCB750K1979]

There is a plastic tee between carbs 2 and 3 pointing upwards.  What does this need to be connected to?  I think this is the vent from the fuel bowls, but not sure.

[Hoosier Daddy]

Yep, that's what it is, a vent. There can be a hose attached but goes to nothing.