Wilber,

I don't know what is exactly wrong with your rig, but if it were me, I would go through some carburetor tuning steps and just see if that helped.

A ballpark figure for the idle air mixture screw is 1 1/2 turns out. I would slowly adjust this until I got maximum RPM, then open it about 1/8th of a turn.

I would set the warm idle at around 500 to 550 RPM and make sure the return spring brought it properly back against the screw.

If you're able, it wouldn't hurt to pull the top of the carburetor and check the float height. After you are all done and back together, make sure everything is tight and there are no vacuum leaks.

You could pull the line to the vacuum advance and use your mouth to pull a vacuum to see if the diaphragm is intact.

Do all these things and see if the problem is solved...if not, formulate a plan B and carry it out!

Stuart