Another engine problem thread

I have a Ryobi weed whacker, 2 stroke, 10-12 years old. It sometimes spends years unused in a shed with gas in it, but has always run ok before. Last time I got it out I replaced all the fuel line as it had disintegrated. After that, it starts fine at full choke, and idles and revs at half choke as one would expect. When I flip the choke full open, it initially runs great - full power/speed. But then if I let it drop to idle and then rev it again, it goes "bwa" like it's starved of fuel and dies. I can keep starting it and running it at half choke (lower speed and power, of course), but can never get any extended use with the choke open. Fuel filter is clean, and I tried running some seafoam through it to no avail. I tried adjusting the carb screws, but that didn't help. Might it be something inside the carb? I reckon I can figure out how to rebuild one.

Check for exhaust restrictions. Wasps like to build nests inde mufflers.

Often, when plastic fuel lines fail, bits of debris head for the carb and get trapped in the screen in the pump chamber. Likely to clog the screen.
With luck, you can pull the cast-alum (vice stamped sheet-steel) pump cover over that chamber and clean the screen with carb cleaner.
The age of yours tells me the diaphragms might be getting brittle. Diaphragm carbs live in a separate universe from all others, but they can be rebuilt. Note very carefully the exact position of diaphragms, etc. on disassembly; they vary, model-to-model.
Be very cool with compressed air.

I worked on my inlaws ryobi sounds similar to there problem after replacing the fuel lines I found the primer bulb had a small crack in it where it was sucking in air. Replaced it and it started to work after that. There's was a 4 stroke model yours might be different.

check primer bulb and replace spark plug.