Adjusting the idle circuit screws and the low throttle stop will do NOTHING to help a set of dirty carbs run better. Remove the entire rack, clean them like it is your last day on earth, reinstall them, and then set the screws and stop. Use the search function for endless good advice on carbs. If you are going to ride a motorcycle with 4 carbureters, you will be an expert when it is all said and done.