Basically the same yes.......same quality control for all manufacturers......I'm not 100% all the way on this one but ..........
I have 5 engines and some of them had much smoother better looking castings and much cleaner ports than others, it seems that there may be some very small mom & pop operations that are turning out different quality engines than maybe some of the bigger operations.
Also I have 2 engines that are made for the larger front down tube bikes, only person I know that sells these engines is BGF/LuckyEarlyBird, to the best of my knowledge no one else has ever handled them that I have seen, correct me if I'm wrong on this.....Shrug!
Check out this link and then you will have a better idea of just how many manufacterers there are and how much of a mark up there is on these kits from the way it looks to me.....
LINK : http://www.alibaba.com/showroom/80-c...le-engine.html
Just my thoughts NOT a solid claim by any means....!