Motorcycle Repair: 1979 Honda CB650, vent hoses, vent hose

Question
I am restoring my fathers Honda CB650 and I am stuck.  The honda will not run without the choke on.  The carburettors have been thouroughly cleaned.  I do have a hose that links between 3 carbs and comes up like a vent hose and I am not sure what it connects too.  I have the owner workshop manual but am unable to figure out this hose.  Could this be my problem?  Any help will be appreciated.
Thank you

Answer
Mike, be sure that the petcock, fuel screen and fuel tank are all clean and can freely flow fuel to your carbs.

http://www.cmsnl.com/honda-cb650-1979-usa_model472/partslist/E++18.html  shows parts illustrations.   You have two bowl vent hoses that go up, 4 bowl overflow tubes that go down off each carb fuel bowl and one fuel feed line going to the petcock, which is between carb 3 and 4 (#9 part).

Bill Silver