Before you do anything else, confirm that you have a clutch pushrod seal installed in the rear end of the transmission. That part is #18 on this diagram:
http://store.bobsbmw.com/microfiche/DisplayImage.aspx?Size=Full&Type=Z&ImageID=3084The clutch pushrod seal part #2312 1451024 serves two purposes. First, it prevents gear oil from traveling from the gearbox to the clutch bell housing via the pushrod. Second, it serves as a pilot bearing for centering the pushrod in the rear end of the shaft bore. If it's not there, well, I don't know what happens if it's not there but the rod probably won't be centered and might not get seated in the bearing at the front face of the puck/piston. If the rod tip isn't seated in that bearing it might just press up against the front face of the puck//piston and prevent the puck/piston from retracting into the bore the way it should.
Everything you want to know about the clutch pushrod seal is here:
http://www.motobrick.com/index.php/topic,5183.msg31947.html#msg31947I hope that's it -- you might have a hard time convincing folks to disassemble their bikes to measure the pushrod for you :2thumbup: Not everyone has an extra bike fully dissembled lying around. Most people that do wouldn't be able to find the pushrod in one of those boxes, just like I can't. But if this doesn't solve it let me know and I will go find the thing and we can figure out what's going on.
I'll bet you're missing that clutch pushrod seal!
BTW if you are and have to get a new one, get two. They're a bitch to get in. Read the above thread thoroughly before you decide how many to order!