Clean the needle valve and the brass piece it sits in that regulates fuel flow into the bowl. If float height is right, more then likely sediment is on the rubber tip or on the brass, not allowing it to close peoperly.
Or replace just the needle and seat for like $12. Or u can get a rebuild kit fir $15 that includes said seat/needle valve. A gasket stock jets and needle/clip. Airscrew and bowl drain screw.
http://m.ebay.com/itm/181279686531 this is 2 kits. One for each carb. I paid $15 each for shindy rebuild kits.
This is assuming you have stock carbs
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