Hy Chenzo, could it be that ice is forming around the carb base restricting flow until the engine warms up? Is your heat riser/spring working correctly?
I doubt it's an ice issue. It's already in the 70's here in Tucson and it's been very dry (less than 10% humidity). My 1955 1/2 doesn't have a heat riser, so there is nothing to check in that department.
