Rear Main Seal Replacement

[roadmaniac007]

1994 K1100LT --I'm performing a 55,000 mile overhaul which includes a clutch replace, spline lube, Seal, etc. Have most of it covered BUT, I understand on some models the New Rear Main Shaft Seal is installed with a .5mm lip protruding rather than a flush-mount.—I dealt with this on my 85K100 with success  :2thumbup: In this case, 94 K1100, I've contacted Fort Lauderdale BMW Service and the response was " uh, well we just put it back the way we found it". Ok, I'll buy that...or should I? Really don't want to open this back up, if I can prevent it.  :falldown:

The Rear Mail Seal is BMW OEM 11117666186. It did not come with instructions to install to within .5mm. (as did my 85K100 seal install)—which makes me feel better about FLBMW's answer...

Question is does anyone have info, and /or know why some Rear Main Seals (or bike Models) incorporate this .5mm setting and some require a flush mount? Is this simply a matter of OEM vs Aftermarket or 3rd party parts?

Can't find any real answers online—hoping you can help :dunno2:

 
94 K1100LT
89 K100RS SE
85 K100RT

[TimTyler]

Applies to all K's that were manufactured or in production when this bulletin was issued.

http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/K100-service-bulletins-and%20special-tools/2798.pdf

Problem: Leaking sealing ring at output shaft.

Cause: An unfavorable set of tolerances may cause the sealing lip of the shaft
seal to rest partly on the chamfered area of the clutch support, with the
effect that a perfect seal cannot be ensured.

Action: Effective from calendar week 14/97, the shaft sealing ring on production
motorcycles will be installed with a projection of
0.5 + 0.1 mm towards the engine block surface.

Service remedy: If a complaint is received, the shaft sealing ring is to be driven into the
engine housing so that this amount of projection is assured.
Modification to special tool BMW No. 88 88 6 111 630

[roadmaniac007]

Most Helpful.  Thank you.   :2thumbup:

 I'm surprised it was not easier to find...maybe I'm just the last to know :dunno2:

I can now install with confidence!

[enialb2]

How is your refresh going?

I'm doing a similar job at 45k on my '91 K75. Clutch is at 4mm, so I'm going to leave that in for now, but am replacing the rear main seal, clutch o ring, and gearbox input shaft seal (which as leaking, I think). After that, splines, new fuel hoses, breather tube, valve check, and some chasing down of engine case seepage with RTV.

First time really getting deep into a K bike, so it has been super helpful to read through everyone's progress.

[Laitch]

Clutch is at 4mm, so I'm going to leave that in for now

My manuals have 4.5mm as the wear limit for the friction disc. 4mm wear exceeds the limit, blaine.

[enialb2]

Ah, late night mistake I think. I believe I'm at 5mm then. +.5 above the limit. Thanks Laitch!

Must double check that though, putting the clutch and a new o ring back in is next on my list since I got the main seal in last night. It wasn't pretty, but it's in.

[Laitch]

Double checking is good—especially after late nights and weekends!

[roadmaniac007]

Overhaul going well, it's a field overhaul :2thumbup:.a challenge at the very least.
Waiting for new trans switch, then swing arm and on.    Splines are near perfect! @ 55,000.  :clap:


Cheers!

[jjs1234]

OK glad I read this post. I was for some reason under the impression that the main output shaft seal was to protrude 5mm ish toward the clutch. But this says towards the engine block which would be the front of the motorcycle.

I bought a tool to put the seal on from one of the members here on the Forum and I'm hoping I won't need to do anything except put it in.

Sent from my HUAWEI MT7-L09 using Tapatalk

[TimTyler]

I was for some reason under the impression that the main output shaft seal was to protrude 5mm ish toward the clutch.

I think it does.

Well, actually 0.5mm.

[Laitch]

Exactly like this.

[jjs1234]

Well I could use a little advice...

First time using Tapatalk but I think the pictures I just took show a seal that is flush with the case.

First picture is of the new seal that I have not yet installed and the two other pictures are of the old seal that is still in the block.

[jjs1234]

Exactly like this.

I see so it is towards the clutch then.

This is the tool that I got from one of the members on here I'm guessing I will need to put I don't know a credit card or something around the outside that might be 5 millimeters?

[TimTyler]

I agree that the PDF language and illustration is hard to understand.

But since there's no way to measure 0.5mm protruding on the inside of the engine we need to assume that the 0.5mm is on the outside of the engine, facing the clutch.

[jjs1234]

Exactly like this.

I see so it is towards the clutch then.

This is the tool that I got from one of the members on here I'm guessing I will need to put I don't know a credit card or something around the outside that might be 5 millimeters?

So it seals here...

[jjs1234]

A credit card is .75 millimeters thick, which makes it too thick for the job-  so if one sheet of paper is .05 millimeters thick then 10 sheets of paper?

Sent from my HUAWEI MT7-L09 using Tapatalk

[bocutter Ed]

One sheet of 20lb bond is 3.5 - 4 thou (.75-1mm). Cigarette paper is 2 thou (0.05mm).

Cereal box board is 20 thou (0.5mm) ...

[enialb2]

I measured a few different thin cardboard boxes similar to cereal boxes, and found one that was .5mm and used that as my depth gauge.

I too had it in my head that the seal would be 5mm proud until I sat down and really read the directions properly at .5mm