Most of the (pumper carbs) walburo, zama, etc. I've seen have a return line so you get to play with extra fuel line it can I think be returned back into its self. But if you take the time the carb that came with the engine works good in my opinion and no extra cost. But I know boys being boys ya gotta make it run faster and jump higher so if ya want tear it up.
You guys want pictures of a carb taken apart and see the insides and what to look for and fool with?
Norman