It takes some work, but it can be done. Since the old buell uses a sportster clutch it has a roller bearing in the basket. A new thrust washer must be made with a smaller od than the stock xb. The thickness is the same. Some relief to the trap door casting also has to happen, the casting has four thick bosses that must be tapered down. The front sprocket and mag must be shimed out as well to achieve chain alignment, only about a mm. The outer primary cover also needs to be relieved at the cover bosses. With the change you end up with a 1.5 to one ratio stock is 1.6 to one. it really makes a big difference at extended 80mph cruising speeds, and is not really noticed at low rpm.