Sounds like you have the dreaded warped "B" airhorn. When this happens, you also get internal leaks which reeks havoc on driveability. Next time it stalls and won't start, pull the spark plugs and see if they are wet with gas.
If you have access to a good carb, you could bolt it on to see if the problem goes away.
BTW, I did witness the tin foil hat solving "Charlie's" issue. I'd like to see if "Olde Charlie's" symptoms would go away with a swap to a known good carburetor. I can imagine a minor internal leak from a slightly warped airhorn being prone to running poorly with a rise in under-hood temperature even if that rise is no more than the normal operating temperature.
But then I am no Jon (carbking).
Carl
