Once the bore inside the slave gets nasty (rusted, pitted, etc.) it's time to throw it away and get a fresh one.
Last night on my way to work I noticed the clutch was engaging really low, and it was a little tough to shift gears. I know we have had several threads recently on slave cylinders going bad, so I figured that was the problem. I got a new one at o'reilys today for $32. It didnt take too long to replace and bleed the system. I am glad I got a new one instead of the rebuild kit. I tried to take apart the old one after I was done, and the boot just tore. It was really really nasty inside too, it looked more like mud than clutch fluid.
Once the bore inside the slave gets nasty (rusted, pitted, etc.) it's time to throw it away and get a fresh one.
the one i got from them is a life time warrantied one. ive replaced it like 3 or 4 times!