My engine is running a set of hs4 carbs:
This is the left hand side float lid (as you are looking into the engine bay):

This is the right hand side float lid:

Am i right in thinking that on the right hand carb you would have your incoming fuel line going in and the outlet would go into the left carb?
Then the remaining output on the left carb would be the overflow incase the floats didnt work?