How does one actually?

Then your disk could be shot, I guess. Just about every used disk I've seen has scoring on it, but yours could be badly grooved.

If you buy a used disk that is not badly scored you may want to have it resurfaced so it works like new. Here's a place that specializes in resurfacing motorcycle disks the proper way. They charge $45 per disk. Ed

www.truedisk.net/