Another problem with Kadron/Solex carbs is the throttle bushings. Grab your throttle shafts, and give them a good shake. See if they're worn.
Many of these carbs are very old, and worn now. As the throttle bushings wear, the throttle shaft and butterfly slop around in the carb throat. This makes them hard to tune, at idle. Blip the throttle and everything moves to a different position.