R100 Rear Main Seal R&R

[Joerg]

Hi,

Originally Posted by bmwrider75

FWIW, BMW does say to never reuse the flywheel bolts, as they do stretch, apparently, when torqued. Same with the driveshaft bolts, though that is apparently less critical, and many reuse them if they thread in smoothly.

May I ask where this information comes from, please?

The factory manual does not mention anywhere that new bolts should be used here, and these are certainly not stretch bolts - neither on the flywheel nor on the driveshaft. If these were stretch bolts, then the instructions would probably read something like "torque to 100 Nm, then add 1/4 turn". Which is not the case.

Originally Posted by PaulRS

In my manual it says it is ok to reuse the old bolts, just torque them up to 130Nm.

The BMW factory manual says 100 Nm. What are you reading ... ?

Btw, full story of my recent crankshaft seal change here: http://jhau.maliwi.de/mot/r80gs.htm#cseal The replacement seal is supposed to be "pre-formed" and oiled before installation.

[PaulRS]

Reused bolts can, I say can end in this



One fokked-up crank and fly-wheel.

Still feel lucky and saving 10€??

Paul.

[AntonLargiader]

I can't be sure, but if those dimples in the seal are hammer marks from installation I would question the entire repair history of that part of the bike. I would think that if they are from the flywheel hitting it there would be other marks back there (such as on the oil pump cover), and there aren't.

[PaulRS]

Originally Posted by Joerg

May I ask where this information comes from, please?


The BMW factory manual says 100 Nm. What are you reading ... ?

Haynes.

@Anton, the seal came loose with the flywheel, I just hammered it back in not to loose the shim behind in transport.

Paul.

[StumpThumper]

Originally Posted by outfit

I did my rear seal last year on a R100 - 1981, so it is the same engine.

The seal was flush to the casing. I suspect if you put the seal in upto the shoulder then you have put it in too far.

Maybe a silly question but, when you replaced the seal you will have taken the 'centre boss' out before the seal goes in? If you did'nt the seal lip will be facing the wrong way.

Safe riding Karl.

I formed the lip around a piece of tubing that was close to the same size as the crank and then used a popsicle stick to guide the lip over the crank when I installed it. I wasn't sure if the centre boss was removable; I haven't been able to move it but haven't tried a puller either.

[outfit]

Just use a hot air gun and it will drop right off. This must be removed before the seal goes in.

I did'nt pre-form the seal but I did oil it prior to putting it in.

When you have the seal in offer the 'centre boss' up and you will be able to see the seal sealing on it. The lip of the seal must point inward's.

The way that you put the seal in mean's that the lip is pointing outward's (not good). The chirping sound may have been crank pressure escapeing via the seal!

This is what I made out of plywood to pull the seal in square.



Safe riding Karl.

[StumpThumper]

Originally Posted by outfit

Just use a hot air gun and it will drop right off. This must be removed before the seal goes in.

I did'nt pre-form the seal but I did oil it prior to putting it in.

When you have the seal in offer the 'centre boss' up and you will be able to see the seal sealing on it. The lip of the seal must point inward's.

The way that you put the seal in mean's that the lip is pointing outward's (not good). The chirping sound may have been crank pressure escapeing via the seal!

This is what I made out of plywood to pull the seal in square.


Safe riding Karl.

No, the seal lip was toward the inside. I used the stick to gently press it up and in around the crank. I used the old seal to drive the new one in place. I'll try the heat gun on the boss.

[StumpThumper]

I just wanted to follow up on this thread after I put some miles on the bike. I found a couple of polished areas on the flywheel where it mates to the crank boss so I was pretty sure it was moving around at idle. I cleaned both mating surfaces to make sure there was no oil or other manner of lubricant on them and assembled the clutch using new bolts torqued to 960 in/lb.
This indeed fixed the chirping sound and everything is working just fine. After a couple hundred miles no leaks and nothing but solid BMW.

thanks for all the input.
gary

[bgoodsoil]

Originally Posted by PaulRS

Reused bolts can, I say can end in this



One fokked-up crank and fly-wheel.

Still feel lucky and saving 10€??

Paul.

I wish you'd stop putting that picture up on here. It makes me a little sick to my stomach every time I see it.