The Carter/Weber carburetors are quite problematic, even on original applications for which they are calibrated. This was Carter's "price leader" carb for the companies which would not pay for the YF/YFA. Much as I dislike saying anything good about the Rochester B; if I had to make a choice between the two, it would be the Rochester B. It is my understanding that when Carter shifted production to Carter/Weber, the castings were vacuum cast rather than pressure cast, producing a poorer quality casting.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop