There concern was not that they're V Twin. They are concerned that for all practical purposes the Yamaha is truly air cooled while most, if not all, of the others are a combination of air/liquid cool of some type. As I'm sure you know, air cooled engines expand and contract more than liquid cooled engines and (supposedly) are less reliable. I know someone will chime up that they know of an air cooled V Twin with 500,000 miles on it but that was their concern.