Pull the hidden filter and clean it. I recommend you pull the hidden filter and install another inline between the tank and carbs that can be serviced, otherwise, just clean and reinstal.
When you cleaned the carbs, did you notice any crud in the float bowls?
How many turns were the idle mixture screws turned out? I'd consider what Steve mentioned previously.
Have you done any recent modifications to the exhaust or intake without rejetting the carbs? Could cause a lean condition.
