I think the problems with B's come about when people try to rebuild them and overtighten the air horn screws, distorting the gasket surface. Another problem is that not many people really understand how the power valve system works and damage it or don't get it properly rebuilt. A problem I've had with mine is that the float bouyancy tends to be iffy (the floats are really small) and the carb floods with the most miniscule speck of debris or overpressure from the fuel pump. They also tend to be really sensitive to float adjustment. Other than that mine works pretty well, the auto choke works (it's off a '66 250), the idle and mixture is pretty consistant, and the thing never ices or plugs up. I always get about 15 mpg in the city and I can burn the cheapest unleaded gas I can find.
