Talk to either Jerry Hall (motorgeek) or Carl(Iceracer) I won't recommend any other builders beside those 2. Jerry is out west and Carl in the east. Call which ever one up, they will tell you how to check it, then all you will have to do is send your head. It doesn't cost a lot to have done. Your bike will be more reliable, easier to tune and a little more power. It is a must with these old Zuki's.