In the process of a rebuild and find that the clutch plates have a fair amount of rust (bike sat outside under a cover for a couple of years before I got it). It looks like it will clean up pretty well with emory cloth but I am wondering just how "smooth" the surfaces have to be to function properly. I would rather not the expense of a new clutch if I can avoid it. The thickness specs on the disc and the measurements on the spring are all well within spec. Thoughts?