HELP fuel leaking?

Pocket Bike leaking gas?
I just bought a pocket bike on ebay. Its a made in China type and was pretty cheap. As soon as I filled the tank with the gas oil mixture it started leaking heavily out the bottom of the bikes over flow tube.

Probably the float in carb which should allow the correct amount of fuel into carb, and cut off once level is reached. Float acts on a needle valve to close off fuel. either adjust small tang on floats to close fuel off earlier or as already mentioned, a small piece of grit might be preventing needle from doing its job.

Lots of those chinese bikes suffer from poor build quality. Notify the supplier and see if they can offer you any advice. You might have to isolate the source of the leak and seal it yourself though.
Did you fill it up too much?
plug it with J B weld after you drain the gas and clean it with rubbing alcohol
Dirt in the float needle & seat.
Stuck floats.
Loose, or leaking float bowl "drain screw".
Clean the carb.
Now you know why it was so cheap.