Thanx again guys, this site kicks ass! I really appreciate the feedback from the real experts around the world. My problem was that I just had it rebuilt and it leaked on first ride. I had ridden it thru alot of new trails, so I assumed that I got somethng wrapped around the sprocket and tore it. When I got the new seal, the old one came right out, but there was no o-ring. My manual covers like mid-80's thru early 90's, 125's, 250's and 500's. I have some extra gaskets and o-rings so i tried a temporary fix with an extra, but it held the sprocket out too far to get the clip in the groove. On my 250, my spacer has a groove in it to accept the o-ring, but the 500 has a square shoulder on both faces. I wondered if it got an o-ring at all, (Which I know now that it does) I assume it must be pretty thin, because the clearance is very tight. Gonna be pulling it back out again to get it right. This time I have a dental pick to pull it out too, tanks to Redlined 's tip. Later!