I know nothing about CV carbs so hopefully someone can help...My buddies bike started sputtering a few days ago. I checked the timing. Put the correct plugs in there and its still doing the sputtering thing. If we use the choke it sputters, in second gear rolling off high RPM's it sputters. Do I need to do a rebuild? Are there adjustments I can make? Its a stock HD CV carb (keihin i think)