Re: Engine almost stalling then recovering
My first thought when surging is encountered would be a vacuum leak somewhere. I'm not sure if the Atomic 4 has any vacuum lines or much of a breather system, but check. You could try listening around for leaks with a pipe, one end in your ear.
Other places for a vacuum leak would be inlet manifold gaskets, either manifold to block, or manifold to carb.
Bristol 31.1, San Francisco Bay