I just purchased a set of used early SU carbs, and while rebuilding them discovered a big problem on one of them. It seems the pressed in bushings (copper I think) that the throttle shaft rotates in our worn to nearly an oval shape, and the throttle shaft itself has two grooves in it. Besides the throttle not opening smoothly I am sure that there would be a major vacuum leak at the end of the shaft. Has anybody else had this problem, and what is the best way to go about fixing it? Are these parts even available yet? Thankyou for any input, Cris.