sounds to me like a clogged pilot jet or pilot air passage but i'm no cb wizz. these passages are what feed air into your engine with a closed throttle with enough velocity to atomize the fuel. the mixture exits in front of the needle jet. the holes are so small that many people don't even realize they are there to begin with. use carb cleaner and carefully wiggle one strand of a copper wire to dislodge the **** (wire brush steel wire or ss safety wire is too big and steel being harder than aluminium will likely damage the shape/size of the hole). blow BACKWARDS with compressed air only if you need to. i like to use the carb cleaner (with straw ) to back blow the passage (the straw pointing down through the top of the carb with the slide removed). use a bright light and a lupe (magnifying lens) to confirm there are no blockages (shine down through the top and look into the back of the carb into the little holes). the pilot jet is easy to to remove, clean, inspect (as above), and re-install. hope this helps...please let us know how you're doing.
ps if you can switch carbs easily and the faulty cylinder switches sides, you know it's a carb problem and not an ignition problem...the bad side will display a wet plug after a minute or two of idling on one cylinder.