leaky o ring:countershaft sprocket.

[Eric and Rheva Lewis]

Conall, If you take off the countershaft sprocket, there is an o-ring waaaaaaay inside that fits around the countershaft that is the culprit. I think the size of the o-ring is 21.5mm and I got mine at Ace. You need to take off the oil collar to reach it. There is no need to drain your engine oil to replace it, but you will have a little spillage, that wipes up with a rag. I had the same leak on my A 8 and it took me forever to discover the source. Now it's bone dry and no leaks. Also, you may want to slack off on your chain tension a little when you button everything back up. Good luck. Eric A 8