I did a long (90 mile, all day) ride in the desert last week and at the end of it I stopped and there was a lot of oil, mostly on the left side of the bike. When I got it home I took off the various bash guards, cleaned it up and checked for where the oil is coming from. It looks like its seeping out around the large nut that secures the front sproket onto the drive shaft. When I reached up to test the tension on the nut it was so loose it turned freely to finger touch. Not surprisingly the last service I had performed included changing from the street gearing (I have the S) to a more dirt friendly 14-48. (That was many rides ago, so it's not that the installer just forgot to tighten it at all). My qeuestions; is the nut being loose alone enough to cause the leak, or is there a seal that is likely blown? is there something that is supposed to lock the nut onto the spindle? There is only a very flat washer behind it, and of course the gear itself is held onto the shaft with splines. (Seems to be on good.) what recomended course of direction to repair?