The side where the cables connect to the valve, the shaft is only kept in place by to spot welds on the headers. Problem is, to reweld the Ti if you do loosen it there to remove the shaft. You cannot remove the butterfly as a whole, as the headers get smaller toward the back! Only option is to drill/ grind it out with something! But then you'll have a 3mm hole on the inside of your headers that need to be blocked up!
You will need to cut the exhaust butterfly in half to remove it. A plasma torch is the best tool to cut it. Remove the shaft and weld the hole with a TIG welder and Ti rod. No HP gains but does smooth the torque curve between 5k to 9k rpm vs just disconnecting the cables. http://photopile.com/photos/wstaab/ZX10R/168799.jpg