Originally Posted by blk-betty
Know nothing about machining. Are those welds "cleaned up" by hand or is it all mechanized?
When I did mine I used a die grinder with a with a carbide cone bit. If you take too much out it will leave the weld weak enough to vibrate crack. Once that starts it will break all the way around eventually. I ended up putting FMF Power bomb head pipe and Two Brothers mid pipe from Jesse at Kientech with my GSXR Can. Works great and the power bomb header has clearance at the frame down tube where the regular FMF oversize header does not. Good set up, very happy with the results.
You can grind the stock pipes' weld for somewhat more flow- which I did at first- but I really don't think it is worth the trouble for what you gain and the run the risk of going too far. I would never do it again in retrospect.