[Caprimaniac]

Hi Tom.

Hope you have it running good.
No, it's not the Webers, it's the condition & tune.... I wonder. You say AF was 18- 21. Was this when idling?
On Idle, the mixture can be quite lean without any danger or problem.
The AF on light, cruise/part and full throttle is what you should check.

On the popping/ not running well issue: In my experience, it is VERY easy to have a too fat idle (idle screws too far out or too big a jet). This will cause the plugs to foul, and the plug won't fire at throttle and hence a stumbling and weak engine. I's not always easy too see this problem by analyzing the plugs. The only way I found to work is to "measure" the temperature of header primary tubes (either by hand (ouch!...) or spit/water, or by an IR- meter). All should be equally HOT! when idling.

On a hot engine very little gas have to enter the throats on idle. (I moved down from 65, as some said to be correct, to 50 in idle jet and finally got the engine to run right.)

RS