I have an '05 YZ450 motor with a counter shaft leak I cannot seem to stop. The bike had a leak there when I purchased it so I replaced the seal, collar and o-ring. First ride out it leaked again so I went back in to check my work, all looked normal, replaced the seal again and she's still leaking. I've discussed this with the local shop mechanic and the previous owner and we've tossed around the usual ideas as to the culprit but I'm throwing this out to you guys for a broader perspective. Just to eliminate some guesses right off the bat, the shaft has no lateral movement, does not appear worn at the o-ring divot and the case where the outside of the seal touches has no visible nicks. And a little history; the bike has a 488 bigbore kit, no other engine problems and the CS seal was all original and never touched prior to this leak. Thanks for your input.