Clean the carb , flush the fuel line , fit inline filter ... if it still leaks ... bend the tab on the float arm up slightly until it stops ... Do it gradually in stages ... a little at a time ... Sometimes the needle and seat can be badly worn from engine vibrations so you end up having to bend the tab up too much to apply enough float pressure to shut the valve off ... and that causes other problems such as fluctuating fuel levels in the float bowl and inconsistent running ... In that case you're best to replace the needle and seat with new parts ...