I put a 4.5 wisconsin robin on a smaller bike a few months ago, and man does that thing snap your head back. I burnt the clutch up in about 2 months but it was so much fun I didn't care. Parts are very expensive, though, I priced an original muffler and it would have cost me $79!! There were no threads in the exhaust port to use metal pipe, so I had a friend customize one for me.