[Craggles]

The condenser is a good point, they can do strange things. Have you checked you are getting a bright blue spark from your coil, I would check all four plugs. I assume once it is starting you are moving the spark rod hitting the accelerator and what effect does that have - it could be too far retarded. By pulling the choke this makes the motor pull fuel into the motor and why I suggested an air leak but it also helps the motor pull it down from the tank which would indicate a restriction or float issue. Dual carbs do change the problem, have you gone through the process with tuning these idle and idle mixtures. Are you sure your cam was set correctly, maybe do a compression test and see how it lines up with the distributor.