The needle shut off valve is not fullfilling its mission. For one reason or another the needle is not plugging the inlet hole when the float is up. Look real close at the tangs that the needle slides on to. sometimes, due to the fine Chinese workmanship, these tangs hit the carb housing before the needle is all theway up, not allowing the needle to seat. It took me a while to figure this one out, meanwhile, FUEL EVERYWHERE!!! Simply bend the tangs to allow the needle to seat further up, I'll do a pictorial If I'm up to it later. Yeah bro, I almost went crazy before I figured this one out. Had to use the shut off valve EVERY TIME I parked it, Or put a bucket under it, ha,ha.
If you cant see what I'm talking about on the tangs, get back to me and I'll shoot some pics.
Big Red.