What Steepndeep said. Your needles and seats are probably bad, also check your Idle Air screws, they should be set between 1 1/4 turn and 1 1/2 turn. While you are in there, carefully remove the pilot jets (idle) and run a twist tie through them, they get clogged easily. Beware that changing the needles and seats is tricky, the Merkuni carbs use pressed float pins that can only be removed safely with an auto punch (spring loaded tool for marking metal), be careful not to break a tab off, it is cast aluminum and the carbs can cost around $250 to replace.