Those carburetors used longer primary metering rods. "B" series is only one style used in them, but the most common.
It is difficult to help with those carbs, they are "remanufactured" and typically "Frankencarbs" or built from parts from different units.
I can supply parts, rebuild kits, and tuning parts IF we can figure out exactly what it is and what's been done to it.
I've been at this over 45 years at this point and to date have NEVER seen one of those carbs that worked like it was supposed to, or even close to being where it needed to be right out of the box. It amazes me to this day that they can sell them without a 100 percent return ratio......FWIW.....