Final Drive Oil Leak

[Ernest T]

I've done a search and read a lot of threads about the final drive leaking oil, but I don't see any threads with a real technical discussion.

Here's what I have.

I rode the bike about 350 miles two weekends ago and have not ridden it since.  I came into the shop and found this today.  There are a few drops of very thick oil on the floor under the rear of the bike.



The oil is dripping from this boot, there is not much oil in the boot, and there is more oil at the front end of the boot where the drive shaft is than the back end where it mates with the bevel box housing. I'm assuming there should normally not be any oil in that boot. The oil is leaking out the front of the boot.



There are a few drips of oil on the rear wheel.



I realize the outer seal is replaceable and the inner seal is not.  How do you determine which is leaking?  Do you have to remove the final drive from the bike to make that determination?  Looking at page 14.13 in the service manual, it looks like the replaceable seal is behind the cap in the bevel box housing and that's where it should leak if that seal is  bad.  How does oil end up in the rubber boot if it leaks from that seal?

I have the mechanical ability to remove the final drive to replace the seal, but before I do so, I want to make sure I understand what I'm looking at when I'm in there.   

[Ernest T]

So after looking at the illustrated parts breakdown, it appears that oil can only get in the boot if the outside (replaceable) seal is leaking.  If the inner (non replaceable) seal is leaking, oil should end up on the side with the wheel lugs?

[Ernest T]

I checked the fluid level in the final drive and found it to be full.  My next step is going to be to take the rear wheel off and see if I can find any oil leaking on the inside of the drive.

[atrophy]

Interesting.  Final drive originally over filled?
Please keep us informed.
Good luck.

[Ernest T]

I took the wheel off and couldn't find a source of the oil.  I was going to take the drive shaft off, but you need a few special service tools to do that so I took it to the dealer for evaluation.  They said they can't pinpoint the source of the oil either, but didn't believe it was coming from the final drive.  They said the rear drive was overfilled with fluid and that could have been the problem.  They drained and refilled and told me to keep an eye on it.

[earthman]

My guess is that it had been overfilled, riding at speed/covering some miles causes pressure to build inside, that's pushed some oil past the seal basically.

[AZBob]

Originally Posted by Ernest T

They said the rear drive was overfilled with fluid and that could have been the problem.  They drained and refilled and told me to keep an eye on it.

It's not possible to overfill the rear drive without being especially persistent.

[earthman]

Originally Posted by AZBob

It's not possible to overfill the rear drive without being especially persistent.

Mine certainly was.

It does make you wonder how they manage to do it though.