clogged idle tubes are a big reason for rebuild not to work, usually crud built up inside the idle tubes passages. Throttle bushings are needed for most carbs because of the wear shafts induce on the base plate. If you have any side to side movement in the shafts you need bronze bushings put in.
You can get unpredictable tuning if there is movement because of a vacuum leak around the shafts.
Also on the top second flaps on the air horn there is a plastic cam lobe that is almost always bad, worn or cracked. That should be replaced always, and also the float too. Most kits don't come with all the parts for a really good rebuild, like accelerator pumps, floats, idle tubes, cam lobe and so on.
Also if you a late model carb you will need to dig out hardened metal plugs covering the idle mixture screws in the base plate if it hasn't been done already. Vacuum test your choke pull off and replace as needed.
There are lots of different things needed to be paid close attention to to do it right, thats why I say get a good book that can guide you through it step by step, and offers tips along the way like idle tube removal and integrating idle air bypass into your carb if it doesn't have it already.
. I knew I'd mess this up somehow. There's the 7 screws taht go into the top, the two screws on the bottom. Where else are there screws?
