Be patient with the flapper valve. The good thing about it being stuck is, at least the holes in the manifold aren't wallered out. (Yes, wallered is a word, just don't try to look it up.)
Spray Kroil, hammer ends of shaft back and forth. Spray more Kroil, hammer, wait, try to move the weight. Repeat. It will come loose.
Don't bother with the carburetor until you can free up the flapper. The carburetor may be fine.
There is an old adage, "Save the carburetor for last. It is never the carburetor." Even if it does end up being the carburetor, you cannot make it work right if there is something else amiss.
Carl
