And after reading your posts in the repair forum...
Do you have an E50 or a ZA50?
You said E50 (one speed) in one thread, and then ZA50 (two speed) in another, so now I'm confused. Usually if you say something in one thread that you didn't mean or that was wrong, it's easier just to post a correction in that same thread rather than making another one. It's less confusing with fewer threads for people to follow about the same problem.
Also, I realize that the distance between your carb and petcock is ridiculously short, but it'd probably be a good idea to see if you can work an inline fuel filter in there somewhere. This applies doubly if your gas tank is at all rusty.