Vacuum Secondaries

IIRC, If this is not a new carb. and someone has taken the secondary spring housing off to change springs, they may have lost the small cork gasket seal. It looks like a cheerio. Without the gasket you haven't any vacuum to operate the unit.
To prevent this problem get a quick change spring unit, with a new gasket, like DesertRat said or what 70aarcuda suggests. Hope this helps.