My wifes was doing the same thing. I replaced the carburetor joints and the vacuum line between the two carbs and it cleared right up. I also replaced the needle and saets while I had them out. Word of advise, unless your experienced with removing the carbs it might be better if you ask a mechanic for help. It took me about 2 hours to figure out how to do it the first time I tried it. But you have to remove the seat, the gas tank, the throttle cable, theside covers, and the EGR system, and the air intake system jst to have enough room to take them out. Good luck