Hello. Being new to motor bikes and not a mechanic or machinest. That said I have been reading these post on the forum till I'm going blind. There are two things I have figured out #1 quality of the HT, #2 there are machinest here on the forum. The way I see it is add #1 + #2= after market Quality. I have no idea what it would take to make a cylender head that is true and to specks or a cylender that is sleeved and ported properly but I can see a good after market bussiness. I,m sure the machinest here have thought about this, but I hav'nt come across any home made engine components on the forum yet. As I said I'm no machenest or metal worker so I have no idea what this would take. Just My thoughts P.S. Don't beat Me up to hard on this just wondering.