Need help diagnoising a rear oil leak...

[j-budimlya]

I could use some rear drive oil leakage analysis help. A few weeks ago when washing my '01 1150GS with 60k miles I noiticed that the right side of the rear spoke wheel had a bit more dirt on it...I thought it a bit strange, but no rear sign of a cause was visable. I have used the bike for a few short rides since and all was well and I sort of forgot about this prior dirt collection on the right side of the rear wheel. Well, ontil this morning that is... Early this morning a few of us road up to Pamdale to watch the send off of the LA-Barstow-Vegas event. It was up at 4AM, off by 5 and arrive in Palmdale at 7 for the 8AM start. For me, it was a chilly ride since I forgot to zip up the vents in my Darian Jacket...thankfully I had my electric vest on or I might not have made it. The start looked to be well attended with 350 riders gathering for the cool start( wait till they see what the temps are tonight!).
Anyway, on the return ride home after a few detours, I stoped for gas and again I noticed an increased "dirtying" of the rear wheel and upon further inspection I noticed that there was now a trail of oil from the lower portion of the rubber boot attaching the final drive to the drive shaft.
The oil was well marked with dirt from our riding on the ash covered roads through the heavily burrned local hills. Still, it looked ridable for the remaining 60-70 miles home. And it did hold together until I got home, but the amount of oil leaking had increased significantly and now had spread to the right side of the tire in a pretty pinwheel pattern. In addition, I now noticed that there was a sign of oil leakage at the upper driveshaft pivit joint, but only a small amount. I have only had a brief chance to check for rear wheel wiggle, and if there is any, it is a small amount. So, my question is, is it most likely leakage from the final drive(either the large bearing seal, or the inlet seal) or is it more likely the rear seal on the transmission?? And what is the best way to diagnose the culprit? I have not had a chance to check the fluid level in the either the FD or the transmission, but I will as soon as I can. And both are lubricated with the same Mobile 1 lubricant and have been changed with every oil change,,,,,so, it could be either place I guess.

Any ideas??

[PGlaves]

I could use some rear drive oil leakage analysis help. A few weeks ago when washing my '01 1150GS with 60k miles I noiticed that the right side of the rear spoke wheel had a bit more dirt on it...I thought it a bit strange, but no rear sign of a cause was visable. I have used the bike for a few short rides since and all was well and I sort of forgot about this prior dirt collection on the right side of the rear wheel. Well, ontil this morning that is... Early this morning a few of us road up to Pamdale to watch the send off of the LA-Barstow-Vegas event. It was up at 4AM, off by 5 and arrive in Palmdale at 7 for the 8AM start. For me, it was a chilly ride since I forgot to zip up the vents in my Darian Jacket...thankfully I had my electric vest on or I might not have made it. The start looked to be well attended with 350 riders gathering for the cool start( wait till they see what the temps are tonight!).
Anyway, on the return ride home after a few detours, I stoped for gas and again I noticed an increased "dirtying" of the rear wheel and upon further inspection I noticed that there was now a trail of oil from the lower portion of the rubber boot attaching the final drive to the drive shaft.
The oil was well marked with dirt from our riding on the ash covered roads through the heavily burrned local hills. Still, it looked ridable for the remaining 60-70 miles home. And it did hold together until I got home, but the amount of oil leaking had increased significantly and now had spread to the right side of the tire in a pretty pinwheel pattern. In addition, I now noticed that there was a sign of oil leakage at the upper driveshaft pivit joint, but only a small amount. I have only had a brief chance to check for rear wheel wiggle, and if there is any, it is a small amount. So, my question is, is it most likely leakage from the final drive(either the large bearing seal, or the inlet seal) or is it more likely the rear seal on the transmission?? And what is the best way to diagnose the culprit? I have not had a chance to check the fluid level in the either the FD or the transmission, but I will as soon as I can. And both are lubricated with the same Mobile 1 lubricant and have been changed with every oil change,,,,,so, it could be either place I guess.

Any ideas??

The oil is coming either from the final drive pinion seal or from the transmission output shaft seal. Either is possible. If that were my bike I would remove the clamp/tie that holds the front of the rubber boot to the rear of the swing arm and peel the boot back. With a good light, look for traces of oil as far forward as you can see in the swing arm. If there are clear traces of oil forward it might be from the transmission. If not, suspect the pinion seal. They often seep a bit and oil pools in the boot. It may take a long time to get there but once it wants out, out it comes.

Then I would thoroughly clean the inside of the boot and the recess around the pinion shaft and put it back together. If you find oil again soon the final drive needs to come off so the seal can be replaced. My hunch is you may not see oil again for several thousand miles, meaning it is seepage and not a significant leak and you can keep your eye on it and clean it up every now and then.

[j-budimlya]

The oil is coming either from the final drive pinion seal or from the transmission output shaft seal. Either is possible. If that were my bike I would remove the clamp/tie that holds the front of the rubber boot to the rear of the swing arm and peel the boot back. With a good light, look for traces of oil as far forward as you can see in the swing arm. If there are clear traces of oil forward it might be from the transmission. If not, suspect the pinion seal. They often seep a bit and oil pools in the boot. It may take a long time to get there but once it wants out, out it comes.

Then I would thoroughly clean the inside of the boot and the recess around the pinion shaft and put it back together. If you find oil again soon the final drive needs to come off so the seal can be replaced. My hunch is you may not see oil again for several thousand miles, meaning it is seepage and not a significant leak and you can keep your eye on it and clean it up every now and then.

Thanks Paul, I hope to begin the diagnosis this next week; but I only have a few days before an extended holiday trip will end the fun of working on the bike. I hate say it, but it could be Christmas before I know what I need to do to get this right. Once I figure it out, I will do what it takes to fix it right.....this bike has lots more miles to go before it will retire....just like me.

[j-budimlya]

After I purchased some dye to make the FD fluid glow in the dark so I could see if this was the problem, I came home and changed the engine oil and filter as a warm up to tackling the leak.....and after the oil was changed, and I started to clean off all of the dust and dirt that had collected on the leaking oil; I noticed some other clues. Bingo, there was more to this then I had previously noticed.

There was a small spot of dirt/oil right under the rear brake line fitting above where the mess was below. How could the oil from below get up there??

Well, after alittle further examination, and some rear brake pressure, damn, it was the rear brake line that was leaking and going all over the stuff below and then down onto the wheel and tire. Bingo! This was alot better than a leaking seal and seemed like a far better problem to deal with......especially since I have been wanting to replace the 8 year old rubber brake lines for a while now.

So, this has a relatively happy ending....new brake lines will be ordered on Tuesday...SS braided of course.

I did replace the tranny and FD fluid and they both looked great as usual. :D

Thanks for your patience and advice.

[bikerfish1100]

careful observation is the key to successful work. nicely done.
also makes a good case for regular bike cleaning, which can force us to look in all those little places for funky things.