by the way im not sure if its called the secondary barell or what but its the barell furthest away from the engine and the opposite barell to the one with the choke and seems to control low revs

my carby is stuffing up
the problem is that the secondary (opposite to choke barrel) is not opening with the throttle. for this reason its choking down low in the revs but if i have the choke out it takes off ok. and when i open it manually with a screw driver it feels fairly stiff but it feeds it fuel properly and the car seems to run ok from what i can tell. anyway my question is does anyone know what is making this occur, is it simply jammed, is there a missing link to this barrell etc etc? and what is the easiest way to fix it, would a carby kit include the peices to fix the problem or is it a throw out job? by the way its just a standard L18 carby with a manual choke. any help would be much appreciated