So... how do you do it? I know the results of it, but I was curious how to actually check to see if it's spinning. I was thinking of pulling off the slave and starting the bike in 1st while on a rear stand. Starting the bike while it's on the rear stand is generally not a great idea though.
On a side note, old monsters FTW! Had a needle bearing go bad and it caused my push rod to drill my slave. Once again the little extender pill for the short push rod saved my slave from getting destroyed. Props again to Yoyodyne for fixing up my leaking slave for the 2nd time due to drilling.
Couldn't you just make a mark on the push rod end on the clutch side, then start the bike and throw it in gear on the stand to see if the rod is spinning?
If you're actually trying to check if the throwout bearing is bad, just take off the pressure plate by removing the six springs and feel it with your finger. It's easy enough to tell if it's still good or not.
I had one go out a few years ago, taking the clutch slave with it. That bearing is cheap enough and easy enough to replace that it should just be done every once in a while. I can't remember exactly, but the bearing was on the order of ten bucks or so. Not nearly as expensive as rear wheel bearings at $30 each (times two).
Engine running, in gear, no clutch, on rearstand = bad idea
As Scott said, just check the throwout bearing.