I have a NOS Carter Zip-Fit Carburetor YF 3211. It was complete with the heat stove and all the fittings. The carburetor runs great with the exception of initial hesitation upon acceleration. I have to feather the throttle, and then the engine takes off and accelerates strongly. The engine cruises down the road very well.
I have replaced the diaphragm in the accelerator pump. I can see gas squirt in the throat of the carburetor while pumping the throttle. It acts as if still not pumping enough gas. Are there any check valves or passages the carburetor that can cause these symptoms? I have leak checked the exterior of carburetor with starting fluid and found no vacuum leaks.
The engine is well tuned; it ran ok with a leaky Rochester carburetor.
Any ideas would be appreciated.
