1st time digging this deep into this bike. Doing a check  on the main seal, checking the clutch,all seals and a spline lube. May have some OMG   posts on here as I am still a little bit apprehensive about it.

Do the o-ring for sure while you are in there.  It seems it isn't as robust as the rear main seal.  If you don't, it will start to leak after you put everything back together.  You can get them at any bearing supply shop.  Go for Viton. 

I have done that o-ring on every bike that has wandered through my garage, but only 1 main seal.  None of the 5 bricks I've owned have had leaks at the back of the engine so far.

I purchased my 1985 K100RS in December 2019. It was my first ever BMW. That winter I pulled it all apart, just like you are doing, as I needed a known point of current maintenance before I started riding it. I rolled in on to my Kendon bike lift and away I went! Mechanically, I found it to be a very straightforward bike to work on.

"That winter I pulled it all apart, just like you are doing, as I needed a known point of current maintenance before I started riding it."

I started that habit some twenty or so years ago. The only bike that has not been subject to a teardown before use is the Royal Enfield and that was only because it was new. At just two years old it's now playing silly buggers with the charging system. Should be a warranty repair but... as the shop is no longer an Enfield dealer, the nearest warranty shop is across forty-three miles of water. Not gonna happen.

That is one thing about the bike. I have found it to be pretty easy to work on. These seem to in most areas make a bit sense. With you tube a manual and this site I feel pretty confident with this project. Funny how as soon as I tore into it the next day temp went up to 60 degrees F!  Great riding weather.

Point-Seven-five wrote:I have done that o-ring on every bike that has wandered through my garage, but only 1 main seal.  None of the 5 bricks I've owned have had leaks at the back of the engine so far.

My experience has been exactly the same, except I've only had two wandering bikes—one was a Honda and the Brick didn't need a main seal.

The worst one I had was a Honda v65 Sabre. Was a PITA to work on. That thing would roll! I have all the  o-rings and a main seal so if something is leaking I should have it. Got the boot for the clutch arm also. The few times it has leaked I found gear oil 2 of the 4 times and motor oil 2 times. Will know more tonight as I am going to continue tearing it apart.

was pleasantly surprised at the condition of the driveshaft and associated splines. Very little wear on them. Ready to pull the tranny off. Will be tomorrow. The boot for the clutch lever was destroyed. That is probably where the gear oil leak was coming from. So far so good. Was faithfully bagging and labeling all hardware until I forgot 4 bolts. Will  figure it out as I reassemble.

Ok I have reached the main seal. There is a lot of gunk and crud there. The o-ring was shot and broken (like me). How do I know if the main is bad or was it the o-ring.

fishboy316 wrote: How do I know if the main is bad or was it the o-ring.

Replace both to eliminate uncertainty.

fishboy316 wrote:How do I know if the main is bad or was it the o-ring.

If there's oil inside the clutch basket (clutch housing in parts diagram) then it's coming from a bad O-ring.

If there's oil dripping down the back side of the engine (in front of the clutch basket) then it's the rear main seal.

Thanks for the reply's gents. I do have both so I guess I will replace both. It really does look like oil is Everywhere. I have it mostly cleaned up but what a mess it was. So what is the recommended way to remove the main?

I also find the clutch plate edges to be a mess. Didn't have any issues with the clutch before but did find oil on a little bit of the plate. It is between 5.0 and 5.3 thickness in different areas. Thinking I may just go ahead and replace it. What do you guys think?
 
Thanks 
Bill

Thanks Laitch, I appreciate the help. I am a little confused on the direction thing. How many ways can this seal fit? Also my seal came with a white plastic insert in the center, What is that for?

Run a couple sheet metal screws into the old seal and use a pry bar to pull the seal out.

Not sure what you mean by "white insert".  Can you post a picture?  Some Viton seals need the inner lip expanded slightly before installation so they can shrink back down to make a tighter seal on the shaft.  Some owners use a pill bottle from the drugstore to stretch the seal for installation.  I just clean the shaft real well and put a lot of Vaseline on it to help the seal slide.

Shaft rotation direction must be a "BMW thing".  I have never seen a marking or worried about rotation on any seal I installed.

I made a seal installation tool with a block of wood and a chunk of cardboard from a cereal box that was about 0.020" thick. 

Trace the outline of the seal on the cardboard and cut out the center so the hole lets it slip over the seal. 

Get the new seal started in the engine and slip the cardboard over it. 

With a block of wood, gently tap the seal in.  The cardboard will keep the seal 0.020" proud of the face of the engine.

The reason you do this is to avoid the lip of the new seal running in a worn groove from the old seal that may be on the engine output shaft.

Assuming your new seal has no spring on the inner lips, then I would suggest the white plastic insert is to 'set' the lips of the seal prior to installation.

Mike

Notice the grooves on the inner face of the seal for guiding the oil back away from the front of the seal are at an angle. 

Looking from the front, the crankshaft turns anti clockwise on bricks, that's unusual. But that means the output shaft turns clockwise, therefore anti clockwise looking from the back. I can only see one photo on this thread but the arrow should be anti clockwise. This seal should only be used on engines where the shaft turns anti clockwise through it. If it was clockwise the grooves would be in the other direction.

If there aren't any grooves, it can be used regardless of turning direction, then there wouldn't be an arrow on it.

The width of your new seal might be different from the existing one.

The new seal had no arrow. Makes sense though. Thanks Daveyson.  I installed the new seal looks good so far. used a short piece of 4x4 with a 3/4 hole in the center. Worked great. I did end up going out and buying a seal puller. Well spent $8. Seal came right out. I also did the cereal box thing .75. This has all seemed to work so far.  The clutch has various different thickness measurements. Had a little bit of oil and gunk on it. Measured from5.05-5.01. Thinking should be replaced since I am this deep. Or should I wait and make sure it isn't leaking anymore? That's exactly what the whit insert was Mike. Thanks

I'd re use it. Brake clean is one of the ways to help get oil off the clutch.

At 5.3 to 5.1mm your friction disc is within the spec of 5.3mm +/- .25mm with a wear limit of 4.5mm.  It's almost new.

I have done the Brakleen wash followed by a light scrub with 220 grit on a block followed by a second Brakleen wash followed by a final light scrub with the 220 grit.  Use lots paper towels to wipe the surface down.

You mentioned above that there were no clutch problems, so I would figure the disc is okay.  Just make sure it's really clean.

Waste not, want not...

Ok Thanks guys. The disk has some rivets that look as though they could be getting close to protruding above the disk. I am a little worried about that.  When I measured it was across the whole friction plate. That correct? 

Thanks
Bill

I had the same reaction about the rivets the first time I saw a K clutch plate. From my experience the clutch will start noticeably slipping before it wears down to the rivets.

Cool, I am canceling my order. Will put her back together. Thanks for the advice folks.

Bill

  Spend your money on fuel, not parts.

What Duck says. Been there, done that. IIRC the plates were down to something stupid like 4mm.

Order cancelled. Can use that money for parts on my shock rebuild. Have reinstalled the clutch. Question is should the friction plate be able to move or not? I am thinking it shouldn't be but but better safe than sorry. Only dumb question is the ones not asked.

Thanks again folks!

fishboy316 wrote:Question is should the friction plate be able to move or not? I am thinking it shouldn't be but . . .

Tell us why you think it shouldn't be; we'll tell you if you're correct and we'll all learn something ; otherwise, I'm going to post a glorious, two-sentence, treatise chock-full of hypotaxis about how a 2V Brick clutch operates. You've been warned.

Your friction disc better be free to slide on the splines.  You have been warned.

fishboy316 wrote:Well my thinking was that it isn't all the way together and the clutch can't be engaged.

A slightly more coherent way to put that could be, the engine and transmission are coupled with the clutch engaged; the clutch will only be engaged if its friction plate is clamped between the pressure plate and the clutch housing cover.

Thanks Laitch. It made sense. Not always the most coherent speaker(writer in this case). Will be starting the reassembly tomorrow eve. The rear main is replaced, the new o-ring is on, the clutch is in. The tranny is sitting on the alignment pins and waiting to be torqued. Then the rest of the stuff. One of the benefits to doing this is I have been able to clean connections and reroute several thing that have been moved over the years. Hopefully it will be smooth sailing. I have actually been enjoying this job. 

Hey .75 What do you mean to move on the splines? When I hear you have been warned I may want to clarify what you are saying.  

Thanks you guys
Bill

fishboy316 wrote:The tranny is sitting on the alignment pins and waiting to be torqued. Hey .75 What do you mean to move on the splines? When I hear you have been warned I may want to clarify what you are saying. 

Is there something beneath that transmission supporting it? You have been warned.

MAN I am getting all kinds of warnings today! It has a jack under it. Thanks for the warning!

The friction disc has to float between the pressure plates so it can fully engage and disengage.  Otherwise it will slip against one or both of the plates and wear excessively. 

If it can't float it will wear out prematurely.  The warning is to not obstruct the friction disc movement.  That is why you lube the clutch splines.

fishboy316 wrote:Have reinstalled the clutch. Question is should the friction plate be able to move or not? I am thinking it shouldn't be but but better safe than sorry.

I think you're saying that you tightened the clutch components to the clutch basket and the friction plate still moves. I think you're right, it shouldn't. Maybe you installed the diaphragm spring the wrong way around, then it won't be able to apply pressure.

I installed the clutch and it does not move. splines are lubed and it was able to float until I torqued  the clutch bolts down. I think it is as it should be. Aligned with alignment tool.

Thanks 
Bill

As long as the friction disc didn't need to be forced over the transmission input shaft it should be fine.  When the bolts are tightened, it will be held firmly between the pressure plates.

You're in good shape.

It went together rather easy. Am actually enjoying this project so far, except when I got my finger between the bell housing and the transmission .   Coming together.

You are learning that the Brick is one of the easiest big motorcycles to work on.  The engineers did a good job on our machines.

Indeed they did. Love my brick!

Point-Seven-five wrote:The engineers did a good job on our machines.

Except for the worthless helmet lock, stock seats and the crappy K75S headlight. But at least they addressed the seat thing by coming out with the comfort seats.

I will give you the helmet lock.  Personally, I hang my helmet off the bleeder fitting on the ABS modulator.  So far, no one has bothered to bend over to steal it.

The headlight on the K75S is just an innocent victim of early 1980's styling and lighting technology.  At the time, it really wasn't that bad.

And the seat, typical German upholstery work.  Not sure what they were thinking when they designed seats in the Fatherland, but they were apparently very afraid of being swallowed up when they sat down.  The unforgiving firmness of the materials seemed to be a hallmark of German automotive upholstery in almost every German vehicle I ever sat in prior to about 1985.

Along with the heater in the air cooled VW's, I suspected the real design goal was to toughen up the German people for the next military adventure into Russia.

You can actually use the helmet lock if you use a short piece of chain which I did.  A mate then told me that back in his day if you left your helmet hanging like that you could end up with a helmet full of pee. It must have been a QLD thing I never heard about it in Victoria. However I now put my helmet on the mirror secure it with a helmet lock to the handle bars, just in case an old Queenslander wants to relive his misspent youth.
Regards Martin.

Imagine what you would find if you left your helmet in San Fransicko!  You might be grateful they only pissed in it.

Aside from how clumsy it is, why put a helmet lock directly above the exhaust? (Which will  be  max hot when you park the bike.)

I lock my helmet up but putting the end of the strap in either a system or city case and then lock the case.

 That is some funny stuff!

I just do not stop/park were there are shady characters about.

I'm still looking for a better bike than a k75!

caveman wrote:I'm still looking for a better bike than a k75.

????? 

I guess we all need an impossible dream to chase.

caveman wrote:I'm still looking for a better bike than a k75!

I have it and you saw it when you stopped by a few years ago - a Lufty K75 turbo with Lufty high performance  cams.  Eats R bikes for lunch.