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.