This is a video explaining why your carburetor is leaking and how to stop it with a small adjustment. (for 49cc bikes)
By bending the forks on the carburetor downward (not too much), you can stop the gas leak. If you make this adjustment and the bike does not start, you have bent them too much and gas is not filling the carburetor bowl up enough. You must then bend them upward a little to allow more gas to fill the bowl. To see how much gas the bowl is getting, turn the white gas flow knob sideways to shut off the gas flow. Then unscrew the bowl center screw to allow the gas to pour out. collect this in a container to measure. If little gas pours out, you know the forks are bent too much and there is not enough gas entering the bowl to start the engine.
