Rear Drive Temporary Leak....

[wildbears]

SEE POST #12!!!!!

Found a puddle of oil under the rear drive area, maybe a tablespoon or two's worth.

Cleaned up.

No further leaking so far.

Occured while bike was on side stand for a few days.

Usually on the center stand.

Any ideas???

'02 K12RS with 65k miles.

[cabnfvr]

Was it hot where the bike was parked that day? If so, it could be overfull and just expanded out the vent or by the seal due to internal pressure if no vent exist. BMW has changed the final drive vents and drains so many times I can't remember which has what. If it wasn't hot then, Houston, we have a problem.

[wildbears]

Will try running it on the center stand, 1st gear, until it warms up and then re-check for leaking oil.

It was a hot day last time it was out and it was run hard (well harder than usual).

Thanks for the info.

[wildbears]

Stationary run in 1st gear and warm engine showed no leak!

And there was no lube accumulation in the rubber boot from the previous leak.

Will have to do a high (for me) speed pavement run next.

Web search shows this leak is usually do to the OEM bearing wear.

The DIY bearing replacement, using an aftermarket bearing, works better than with an OEM according to one thread.

[cabnfvr]

If you have the tools the bearing change is supposedly pretty simple, and yes, the aftermarket bearings have done very well. Be sure to check for any play in the bearing by trying to shake the wheel and feel for any movement. There should be zero. If any is felt change the bearing even if its not leaking.

[wildbears]

Got it and thanks again.

Checked and absolutely no play in the back wheel.

[wildbears]

Two part video on changing the K12RS final drive bearings if needed:

2002 BMW K1200RS Final Drive Ball Bearing Replacement Part 1 - YouTube

2002 BMW K1200RS Final Drive Ball Bearing Replacement Part 2 - YouTube

[wildbears]

Took the bike out yesterday and a very small amount of oil was present at the boot. Hopefully just left over from the previous "spill".

Will do another test ride this weekend.

[wildbears]

Longer ride showed oil leaking again. Not as much as the intital burst but enough to indicate a definite problem.

This is a 19 year old bike with 66k miles.

It may be time to put it out to pasture at least for the time being.

Don't have time to do the repair myself now and not sure the bike is worth the cost of having the dealership do it.

[wildbears]

Local service manager sez they typically don't repair the final drives as it is difficult and expensive (several thousand dollars).

He suggested getting a used final drive.

[wildbears]

SEE POST #12!!!

Since the leak is coming from inside the rubber boot and not leaking directly down from the final drive onto the back wheel

AND

Since there is absolutely no play or grinding noise coming from the back wheel, final drive

The most likely culprit is a leaking "pinion shaft seal".

Less likely, but a possibility, is the transmission output seal, which when it leaks it can also result in gear lube in this location.

To determine where the leak is coming from, a UV leak detection fluid may be used by adding it to either the final drive or the transmission.
Available at AutoZone:
https://www.autozone.com/test-scan-a...E&gclsrc=aw.ds

There is not enough space to visualize where the leak is coming from when the final drive is still attached.

And both use the same lubricant so determining source by smell or feel is not possible.

Don't know if this is good or bad news compared to replacing/overhauling the final drive crown bearing, but would think it would be an easier fix.

Here's a link to an excellent DYI Video on removing the final drive: https://www.youtube.com/watch?v=L0_j8SuiFQI

[wildbears]

Final Drive Leaks, Two Most Common Causes

More info that helps with diagnosing the source of the leak: https://www.bmwlt.com/threads/final-...ar-oil.171786/

Final drive leaks, two most common:

At the input shaft: Check by removing the zip tie and pushing back the rubber boot that couples the swingarm to the final drive. If gear lube come out, there is your leak. (Note that transmission output seal leaks can also result in gear lube in this location.

Fix: Replacing the seal at the input shaft isn't for the novice. As a matter of fact, leaks at this location are sometimes related to inadequate thread sealant on the seal retaining "threaded ring" (bmw part # 33 11 2 333 120) rather than the seal itself.

At the crown-gear hub seal behind the brake rotor: (From your description of the distribution of leaking lube, my guess is this is your problem). This is an early symptom of failing crown-wheel bearing.

Fix: Folks who have only replaced the seal in an attempt to fix a leak at this location often went on to have continuing leakage and other problems. Replacing the seal behind the brake rotor should be done in conjunction with an open inspection of the final drive and replacement of the crown-wheel bearing and correction of any other findings.

Note: In one report by a company that repaired final drives, about 1 in 30 were due to a bad seal alone. The remainder had bearing problems.

[wildbears]

Down the Rabbit Hole!!!

Well, I've spent many hours trying to figure out where the "oil leak" is on my '02 K12RS (66k miles).

Fluid was dripping down from and was within the rubber boot where the swingarm joins the final drive.

Pulling back the boot revealed the fluid to extend for some distance towards the front of the swingarm.

The fluid repeatedly appeared after a ride but not when the bike was run in 1st on the center stand.

Initial information from the net suggested a leak at this site indicated a final drive failure. That is, the crown bearing was shot.

But upon inspection there was no play in the back wheel.

Further information suggested a leak from this site was due to either a pinion or transmission shaft seal leak.

So, next step was to add a fluorescent dye to the the final drive lube.

A long ride failed to show dye at the boot.

It also failed to show further evidence of a leak.

See Pics Below (clean and dry swing arm; negative fluorescence).

What had changed was....

A leak in the back brake line rubber hose was discovered and temporarily patched before the ride.

The leaking brake fluid was dripping down onto the top of the swingarm, and due to the shape of the top area of the swingarm, was being "funneled" to the boot attachment.

From there it was seeping inside of the boot and also dripping down onto the swingarm brace and then onto the ground.

So the final drive and seals are all healthy and do not require repair or replacement (was not looking forward to that).

Next step is to replace all of the rubber brake lines on the bike (all are original except for the one coming from the front brake master cylinder that was replaced about 10 years ago). See: https://www.youtube.com/watch?v=1Uj6xDyPTMUchange brake lines brake lines K1200RS ABSII - Google Search

Also see thread @: https://theriderspace.com/forum/tech...eak-at-zip-tie

The first clue I missed early on was the leak onto the driveway disappeared by the next day.

And later, the leaking fluid did not have the pungent odor of the final drive and transmission lube.

It did have the color and slippery feel one would expect with the final drive and transmission lube.

The brake line leak was discovered only after the brake failure warning lights began flashing.

A "stain" on the swingarm (since removed) indicated the exact site.

The leak of course was inactive when the bike was on the center stand and the brakes were not being used.

[aviator]

Elementary, my dear Watson. Good job.