[capnward]

You're right, you should have mentioned that. I once had a problem that the engine wouldn't idle. I couldn't see that the idle jet was partially obstructed until I removed it, held it up to the light, and looked through it. It has been recommended that you file a screwdriver to just the right size for the idle jet, so you won't damage it. It should come out, but if you can't do that, run a thin wire from a wire brush around in it, while it's in the carb. Don Moyer showed that wire trick in his superb video, after removing the jet from the carb. The junk in it may not dislodge with carb cleaner or air. That tiny orifice is so important to keep clean. If there is junk in your fuel, the idle jet will be the most likely place in the carb to catch it. If the opening of it is really mangled, I guess that may affect it as well. Once the jet was clear, the idle came back. Now I take it out every year and check it for crud. That to me is the most important part of carburetor cleaning.
Now I know that there are supposed to be rubber seals around the throttle and choke shafts. I haven't noticed them before. I wonder if I have them...