Engine will run on middle chock, but die when chock is off. please comment.

Your carburetor is probably clogged, this is very common. Once this happens you might try spraying some carb cleaner into the carb and let it soak for a few hours but most of the time you have to remove the carb and disassemble it to unplug any small orifices that are clogged with a small wire. You can pull out a small wire from a wire brush and that usually is stiff enough and small enough to do the job and then spray carb cleaner into it and let it soak for hours. You might also replace the carburetor gaskets and fuel filter and diaphram.

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