While I don't think it is the problem, the choke can be stuck open without obvious symptoms. Mine needed replacing at about 15K. I had slightly increased vibration and slightly decreased gas mileage. A mechanic I trust suggested replacing the choke cable because he believed that one of the choke needles was hanging up. i disassembled the original cable at the carbs, found no problem and reassembled it. Everything appeared fine. I finally replaced the cable and the symptoms went away. It's not the cable hanging up, it's the choke needle. BTW, expect sticker shock ($54 as I recall) and a royal PIA replacing the cable if you go that route.