500 klms or 300 miles is the break in period for clutches. As for how long before it will start losening up, your guess is as good as mine, but keep us informed. If you have high performance clutches it will take a little longer, but one or two hard runs, as in petal to the metal, might take care of it. We are only talkin' .005-.01 of an inch before it will work properly. I beleive the proper clarence is about .015-.02