Is the bog when you have just normal light acceleration or when you just mash the pedal? The fast idle holds the primary throttle blades open until the choke opens to a certain point. You could have a bog if the choke is not working properly and opening up and the choke pull off diaphragm is damaged. Check if the accelerator pump is working properly and if gas is squirting out into the primaries by opening the throttle lever. But don't do this more than a few times on a engine that isn't running or you could flood the engine with raw fuel. This is assuming the carb was rebuilt properly with a new correct accelerator pump and has all its . Proper springs. And also the check ball is installed properly in the carburetor.
