1990 K75S - Rear main seal advice please!!!

[scottishsg]

Hi there again!!

About to remove the nut holding the clutch housing to output shaft and examine the rear main seal.

I have two questions for you gurus!

1: How the heck do you stop the clutch housing from turning? I know on the K100 it has holes you can stick a hammer shaft into so the housing doesn't turn. What needs to be done with the K75? Seems odd they would not use the same housing when many other parts are shared.

2: Replacing the rear main seal. Is the BMW special tool needed for the install? I have read many people say that the seal needs to be curled backward? I've never heard of such a thing. Most rear mains are just installed to flush with the block and move on. Is this bike so different? If I am there, and the rear main looks ok, should I just replace anyway, or is it one of those, if you mess with it you may create a leak type deals.

Now I am on a roll......thought of a third question.

3: The gear position indicator on rear of gearbox seems to be cracked open. I have seen many pictures or others that are similar. Is this something that can be epoxy'd or should it be replaced also?

Thanks in advance for any input!!!

Stu

 

[98lee]

Stu,


1. Cut a block of wood to wedge between the pocket on the left side of the bellhousing and one of the three ears of the clutch housing. BMW makes a special tool for this, but you don't need it or want to pay theprice for it.


2. If it were my bike and I was already in there, I would replace it, especially if it had 50k or more miles on it. I check the shaft where the seal rides, soak in oil for an hour or so and install. If shaft shows wear marks, install slightly offset.


3. If it still works properly, just seal VERY well with epoxy. Water spray off the rear tire is what kills these. Moisture inside shorts out the contacts and give false readings. There is supposed to be a thin paper gasket between the switch and the tranny.

 

[scottishsg]

Thanks Lee!!
Can you please clarify the soaking in oil? Are you saying soak the new seal in oil then install it? Looking for wear marks on shaft as in the seal not touching the shaft in certain spots when installing?

1&3 I can handle lol.

 

[98lee]

Yep and yep.

 

[scottishsg]

Roger that! Thanks again Lee!
You must've taken a few of these bikes apart in your day!

 

[98lee]

Mostly recently. I do a lot of work on local people's early Kbikes. Especially Ss (I currently own 5).

 

[Bobmws]

Does the K75 also use the o-ring under the nut & washer? On the K100 they are usually hard and brittle and a source of oil leaks.

 

[scottishsg]

They do have the o-ring. I am replacing that as a matter of course, was asking of main seal just because I am already that deep, I may as well change it!!!

 

[scottishsg]

Mostly recently. I do a lot of work on local people's early Kbikes. Especially Ss (I currently own 5).

Well..... it's a pity you live on the complete opposite side of the country, or I would be asking for your services here too!!

 

[98lee]

Bob,

Yes. ALL Bricks use that O-ring.

Stu asked about that O-ring in his previous thread: http://forums.bmwmoa.org/showthread.php?74711-1990-K75s-Swing-arm-bearing-play. It was covered in post #4. Sometimes when things get spread between a couple threads, it's hard to know whether something has been covered.

Thanks for pointing that O-ring out to those that might only read this thread in the future. It IS the most common leak point in the clutch area.

 

[98lee]

Well..... it's a pity you live on the complete opposite side of the country, or I would be asking for your services here too!!

I could arrange a ride-in appointment for you.

 

[scottishsg]

Haha one day I'll be doing that trip! I'll hold you to it.
With regards to posts, I figured I would start a new thread so the titles would be easier for people to search with each topic. Should I not do it that way? I mean, my first post was about the shock so it is not relevant to swing arms or rear mains. I want to post the way the majority of forum users prefer.

 

[98lee]

Your fine. Maybe the rear main topic could have been a different thread from the swingarm. That's something I probably could move around if I could find the time and remember how to do it and if it is OK with you.

 

[scottishsg]

Lee,

You can move whatever you need to! Whatever will make things easier for everyone is good with me!!

 

[scottishsg]

Evening all!!

I pulled the rear main seal, output shaft seal. What a bugger. Wish I'd left it alone now lol. Anyway, I installed new one, but it seems to not seat in as far as the original. Is this by design? It's not flush, sticks out slightly. Please advise!!
I'll try to grab a pic real quick!
Thanks! !

 

[scottishsg]

 

[pglaves]

Please tell me I'm wrong, but from the photograph it looks like the lip of the seal is curled rearward toward the transmission end of the shaft rather than forward away from the transmission. If this is the case do not put it together that way. It will leak oil as if the seal isn't there if you do.

That is the "trick of the factory tool. When inserted onto the tool the lip is curled in the right direction and remains that way when the seal is driven forward to the correct position on the output shaft.

 

[scottishsg]

It isn't really curled, it's is just not installed all the way. I brought a seal driver back from work today, fits it perfectly, however I discovered that the snout that goes into the center of the seal was a little too long and bottomed out too early. In my frustration, I just bent the seal using a socket to try and push it the last fraction of an inch. Need to pull it back out and use a new one.
Is there a substitute for the factory tool? They tend to be expensive to buy, especially in this instance where I'll likely use it only once!
Thanks for your input! It's very much appreciated!