Might worth checking the hole is clear in the gearbox breather/battery lead earth bolt before any major undertaking.
This is a specialized fastener with a small hole down the axis.
Sometimes previous owners replace them with a larger screw with no hole, because they stripped the threads.
If that were the case, I would see about getting a machinist to bore a hole, rather than messing with a timesert type thread repair. More than likely this is not the cause, however. Good call, Barry.
Oil moving around between the transmission assemblies is not that uncommon on airheads. When I first got my bike oil had migrated from the driveshaft to the final drive. All I did was use a small syringe to put it back where it belonged and several oil changes later it's never moved again at least not in any significant quantity.
Barry, did your bike sit for a while before you aquired it? It's possible the seals dried up and then repaired themselves to a degree after getting back in service. ?
Last thought did you change oil type or viscosity.
Several years ago I switched to full synthetic for my gear lube needs.
My bike is so messy it's hard to tell if I had any new leaks.
Actually, my final drive has been leaking a lot, last the bike was running. Dry on the inside, though. Let's not go there. Stay on track.
I put the synthetic in there for smoother shifting. I can't honestly say I noticed much change. I kept using it because I read it was more durable for gearbox use, less prone to molecular breakdown. NO, I am not a chemist.
