Rear main Seal Leak--Again! '99 K1200RS

[Kontoboy]

I pulled to bodywork to hunt down and electrical gremlin with my PIAA lights (turned out to be a failed Autoswitch), but with the bodywork off I saw those too familiar signs of a leaking rear main seal--oil at the junction of the clutch housing and engine cases underneath the motor and that telltale line of slime along the joint. So far the clutch isn't slipping, but I know it's just a matter of time.

What annoys me is this is my third failure with just 41 K on the bike (99 K1200RS. The first was with about 34K on the bike. The dealer wanted $1500 plus three months wait time to work on it. I did it myself, but it failed again after just a thousand miles--I blame myself for not seating the seal properly. The second time I had a seal driver made and it went 6000 miles--better but not good enough.

My plan is to wash it clean tomorrow after work, and drive it a week or so to confirm it's leaking at the seal. If it is I'll replace it again, or pull the motor and see if I can have a local dealer replace it if they can do the work quickly.

Hopefully I can get it done in time to get some test miles on the new seal before I drive to Sedalia. If not Sedalia is in jepoardy.

The saddest part of it all is that I'm losing my faith in this bike. Once that trust if gone the relationship is over.

Kontoboy

 

[deilenberger]

svineski/Kontoboy (real name?)

Please read: http://forums.bmwmoa.org/showthread.php?t=46057 - that information is not only missing from the thread title, it's completely missing in your posting.

That information might be quite useful if you're seeking any help or information here.

IF your bike is a K bike, and if it's a classic brick K bike, and if it's one of the earlier ones, you should note that the seal design has changed at least 3 times (might be 4 actually) I know of, and each time, the depth the seal is supposed to be driven into the engine casing has changed. Installing it at the depth that is in the manuals is almost certain to make it fail yet again. I'm sure BMW had TSBs for the dealer indicating this, and sold them new seal drivers for the new seals (at great expense).. so having the dealer do it might not be a bad idea.

I'm also going to assume you've replaced the clutch basket nut O ring each time? That's the actual cause of most "rear seal" leaks on K bikes..

 

[42906]

Before you tear the bike apart to replace the rear main seal, you better check to see if the oil isn't really coming from the alternator seal. When that seal starts to leak, the oil always finds it's way to the seam between the gearbox and intermediate housing. My intuition tells me this is what is leaking and you have been chasing your tail changing rear main seals.

Replacing the alternator seal is something you can do at home and it is a good time to look at the condition of the rubber vibration isolator blocks in the alternator cush drive. Those, too, wear out and when they finally go, you get an awful clacking noise from that part of the bike that is frequently confused with more dire problems.

 

[42906]

svineski/Kontoboy (real name?)

Please read: http://forums.bmwmoa.org/showthread.php?t=46057 - that information is not only missing from the thread title, it's completely missing in your posting.

That information might be quite useful if you're seeking any help or information here.

IF your bike is a K bike, and if it's a classic brick K bike, and if it's one of the earlier ones, you should note that the seal design has changed at least 3 times (might be 4 actually) I know of, and each time, the depth the seal is supposed to be driven into the engine casing has changed. Installing it at the depth that is in the manuals is almost certain to make it fail yet again. I'm sure BMW had TSBs for the dealer indicating this, and sold them new seal drivers for the new seals (at great expense).. so having the dealer do it might not be a bad idea.

I'm also going to assume you've replaced the clutch basket nut O ring each time? That's the actual cause of most "rear seal" leaks on K bikes..

True that! The latest seal has less depth than the ones that leaked and if my friend who is an experienced K bike tech is correct, the latest seal should be tapped in until it's flush with the back of the engine and no more.
The engine output shaft necks down in diameter closer to the bearing and the deeper seals were often driven in just enough that the seal lip passed the larger diameter it was designed to seal against and was over the smaller diameter closer to the big ball bearing.
Don't feel bad, my friend used to work at Research for BMW and when he rebuilt one of my K bike engines he drove the seal in too far and it leaked from day one. I learned a lot watching him work.

 

[osbornk]

FWIW-I had a Brick that leaked at the rear seal with synthetic but didn't with dino.

 

[42906]

FWIW-I had a Brick that leaked at the rear seal with synthetic but didn't with dino.

I run 15W50 Mobil-1 synthetic and have for over ten years with no leaks. I run synthetic oils in all of my bikes and cars, both engines and transmissions, with no leaks. Modern viton seals are very good. The current engine in my high mileage K-100RS has been in there for 77,000 miles and aside from the initial mis-installation of the rear main seal that was immediately corrected, remains oil tight. Leaks have nothing to do with the oil you use.

 

[osbornk]

I run 15W50 Mobil-1 synthetic and have for over ten years with no leaks. I run synthetic oils in all of my bikes and cars, both engines and transmissions, with no leaks. Modern viton seals are very good. The current engine in my high mileage K-100RS has been in there for 77,000 miles and aside from the initial mis-installation of the rear main seal that was immediately corrected, remains oil tight. Leaks have nothing to do with the oil you use.

The oil might have nothing to do with it in your case but it does in many cases. I've put synthetic in both a K bike and an Airhead and got enough oil seepage from both seals and push rod tube seals to drip on the garage floor. I changed both of them back to dino and the seepage stopped. I sold the K bike but the Airhead has stayed drip free for the last 13 years.

 

[Kontoboy]

My apologies for not specifying the bike in the title--it's a '99 K1200RS. I added it to my post but don't have the option to edit the title.

"V i n e s k i" is the real name but KontoBoy (canta for corner) is my general on-line moniker--I just changed it to avoid the prying eyes of search engines.

On the previous seal replacements I did buy the latest seal, but I don't recall if the seal driver I had machined was for the newer seal. That was about 5 years ago!

My seal driver does push the seal past the casing, so if the newest seal is driven flush, I either didn't have the latest seal or if I did, it was driven in too far. I was working mostly off the BMW service manual and forums. We know the manual is dated and the forums aren't always reliable.

I'll defintely specify the new seal and check the depth if I do it myself.

And I did replace the O-Ring and all the clutch basket bolts as specified.

As far as the alternator seal leaking--that could be true this time around. I have no doubt it was a main seal leak before--you could see the oil seeping around the seal when I pulled the clutch.

I haven't dug into it yet but will check the alternator area. I did notice oil on and around the coil which seemed strange and is adjacent to the alternator.

I've used synthentic BMW oil since I bought the bike at about 10K miles.

 

[deilenberger]

My apologies for not specifying the bike in the title--it's a '99 K1200RS. I added it to my post but don't have the option to edit the title.

Not a problem, I'll add it..

"V i n e s k i" is the real name but KontoBoy (canta for corner) is my general on-line moniker--I just changed it to avoid the prying eyes of search engines.

First names are good, or even a first name and initial... just makes for a more friendly place.

On the previous seal replacements I did buy the latest seal, but I don't recall if the seal driver I had machined was for the newer seal. That was about 5 years ago!

My seal driver does push the seal past the casing, so if the newest seal is driven flush, I either didn't have the latest seal or if I did, it was driven in too far. I was working mostly off the BMW service manual and forums. We know the manual is dated and the forums aren't always reliable.

It should be flush, or even standing a bit proud of the case (I seem to recall about 1/16" inch last time I did one..) You can check where it belongs with a caliper measuring into the bearing in the case, then the flange on the back of the clutch basket.

I'll defintely specify the new seal and check the depth if I do it myself.

DIY sometimes is a good thing..

And I did replace the O-Ring and all the clutch basket bolts as specified.

As far as the alternator seal leaking--that could be true this time around. I have no doubt it was a main seal leak before--you could see the oil seeping around the seal when I pulled the clutch.

I haven't dug into it yet but will check the alternator area. I did notice oil on and around the coil which seemed strange and is adjacent to the alternator.

I've used synthentic BMW oil since I bought the bike at about 10K miles.

Also check the starter O ring. That's been known to leak, and the oil will dribble down into the clutch housing and then dribble out the weep hole in the bottom of the case. That one is really easy to fix..

 

[42906]

Oh yeah, forgot the starter o-ring. I had to replace one of those on a trip with an o-ring from a mom and pop hardware store. It's still in there too.

 

[42906]

Off topic. How do I replace my MOA number with my on line name? I guess I'm not too adept using the User CP.

 

[Kontoboy]

An update....

I dropped the motor today and couldn't find any significant oil leaks around the alternator. There was some leaking around the starter O-Ring, but not enough to account for what I was seeing at the bottom of the intermediate housing. Biting the bullet I pulled the transmission, and saw some, but not a great amount of oil in the bottom of the intermediate housing. But as soon as the clutch basket and o-ring came out it gushed oil around the output shaft, the rear main seal showed signs of oil along the bottom third, and the intermediate housing had a very very light coating of oil--almost as if was misted on.

On further observation it looked as if the rear main seal had moved. My seal driver indents it slightly into the rear casing, but one side of the seal was now flush with the casing!!! I know I didn't leave it that way.

Luckily the clutch friction plate was dry with no signs of oil and little signs of wear after 6K miles. Same with the basket. I'll get the calibers on them to double check for wear and warpage, but don't expect to find any problems.

Based on what I've found to date I'm planning on replacing the rear main seal--again--and the associated o-rings and bolts and nut on the basket. I'll replace the starter o-ring too. I'm leaving the alternator alone--no signs of leaks and the rubber bushings look fine.

At least it's getting easier each time I do it.

Steve, a.k.a. Kontoboy

 

[Kontoboy]

A final update...

The main seal is in with a new viton o-ring. When I picked up the seal I checked with the service tech and he said the seal seats just proud of the casiing and put it in dry. That means the one I installed 6K ago, the identical seal, was set too deep! I attribute it to the forums and manuals not being as up to date as the tech bulletins and new parts.

From advice on another forum I picked up some viton o-rings, even though my old o-ring looked OK.

When installing the seal I pulled the motor out entirely. It wasn't that bad a job and it gave me great access to the engine output shaft making it easy to get the new seal in straight, and get the transmission on easily.

There was some oil leaking around the starter, so that got a new 0-ring (as well as thorough cleaning in and out). There was no sign of oil around the alternator.

The other nice thing about having the motor out was the chance to clean the top, get a good look at the timing and valve cover gaskets (all looked fine), check the breather hose (also fine) and thoroughly clean everything.

The did motor come out with the transmission off, but it looked like it would go in with the transmission on. It did, though it did take some manuevering. The motor was on a MC jack, the bike on jack stands and in a Baxley chock.

Got it back together a couple weeks ago--rode it for a couple days, and discovered the rear final drive bearing was going! I saw metal when changing the gear oil, checked for rear wheel play--it was just a matter of time.

So last weekend I pulled the final drive off and disassembled it, pulling the bearing. Luckily I caught it early and the damage was limited to the bearing. I took it to a local BMW shop which did the seal and re-shimmed replacement bearing and check and replaced the pivot bearings too. It was ready the next day and I put it back in the bike yesterday and went for 100 mile shake down ride.

All seems well. I leave for Sedalia on Tuesday morning--1000+ miles straight thru. Hopefully nothing else will go wrong.

Kontoboy

 

[deilenberger]

Have a great trip, and thanks for posting the resolution to your problem, so many people forget to do that after they fix a problem, so we're left with problems and no answers!