I had same problem mounting a 89 motor on a 97 frame the swingarm was 5/8 inch to small and the casing was about 2 mm too small luckily I was working in a machine shop and I was able to accommodate the d**n thing , shaved down the swingarm and bored the casing , the only thing that posed a big problem was for the exhaust to fit in I had to bend it and dent it for the cooler line and front of the frame