I agree with Andy on fixing something online. Don’t know what all has been done. Especially since it’s used. If taken apart, a gasket could’ve been turned wrong (yep, I’ve done this), blocking passageways that are suppose to be open. In your case, if no fuel is making it to the back bowl, it’s either float is sticking causing the needle and seat to close, or the needle itself is stuck closed. Of course this will not let the fuel enter the bowl. Mine usually stick open occasionally and all it usually takes is a few light hammer taps on the adjustment screw and nut. Might try that to see what happens. Still no fuel, pull it out and clean it with carb cleaner and reset float. To me, that’s all that controls the fuel entering the bowls.