So I bought this bike and it runs strong! Lots of fun. I would like to fix an oil leak. It looks like an o-ring that seals a shaft coming from the top of the cylinder head needs to be replaced on the left side of the motor (as you are riding it). I'm not even sure what you call the shaft (rocker arm shaft?) that it seals. I certainly don't know what is involved in the replacement. I think that on some models that there is a plug you can unscrew. This model has a slot (maybe for a flathead) on the end of the shaft. I tried to unscrew it assuming right-handed threads and it didn't want to budge; however, I was gentle. I have a great schematic that points to the shaft and the o-ring. If I could figure out how to post it here I would. I can e-mail it to you for sure, so let me know if that would help. If anyone knows what is involved in this repair (or what that shaft if correctly called), please respond! Much thanks.