So...using a little deductive reasoning, what piece of the puzzle could possibly be the problem? You've replaced the stopper valve (forget what it's called), so it can't be a "leak" there. What did your float height measure at when you checked? Judging by the carb gaskets you used, you have the 022a carbs and the height should be 22mm.
Are you sure the floats weren't reinstalled upside down by someone?