[eschaider]

I would be looking at a fuel in the float bowls percolation possibility first.

If it is happening, you should see some visible signs of the problem with fuel boiling out the various vent tubes and air bleeds on the carb. If this is the problem, a nonmetallic spacer between the manifold and the carb can be used to isolate the carb from some of the heat and somewhat mitigate the percolation problem. The better the insulation, the better the mitigation.

These engines operate on fuel, air and spark. The air component is pretty much handled by the cam and engine displacement. That leaves fuel and spark as domiciles for potential gremlins.

If you have good fuel delivery with proper idle fueling and speed settings, and you are not experiencing a percolation issue then you are down to an ignition problem, and as Sherlock Holmes was want to say, " When you have eliminated the impossible, whatever remains, however improbable, must be the truth." You might well find the gremlin in your ignition system.

My money would first go to a percolation problem, then to idle speed and fueling, before pursuing an ignition issue. Whatever the issue is finally determined to be, my money would be on one of those with percolation in the lead.