Originally Posted by
N1EDM
The "nipple" part 84-5601 is the threaded tube sticking out of the mixture disc. You have a complete early carburetor with needle attached to the carb. The later ones don't have that 84-5601 "nipple" - the mixture disc is just smooth and uses a remote needle. Your needle valve looks correct as well. Maybe the needle is bent? It doesn't look bent in the picture, but pictures don't tell the whole story. Try putting a drop of oil on the needle valve and try working it in and out (as if screwing it in and out). As a last resort besides replacing the needle valve, you could lightly sand the large part of the shank of the needle valve with fine sandpaper and lap it to fit, though I don't think that should be necessary. Maybe try a pipe cleaner soaked with acetone and run it through that "nipple" #84-5601.
If you cannot get the needle valve to thread in at all, let me know and I can send you a needle valve. I have a couple spares.