R65 final drive is apart - question on the brake tube

[gregb]

Hi all. Bike is a 1985 twin shock model. Had a small leak from the final drive area which I was monitoring...until I suddenly lost the rear brake due to excessive lubrication. That was fun in the middle of a u-turn. Anyway, it is removed and apart and I plan to replace the LH oil seal. Only difficulty so far is removing the gasket material. Grrrr.

My question is on the tube through which the brake actuating rod passes. When the cover was removed the tube was firmly stuck in there but I was surprised there was nothing sealing the tube in the cover. It was just a press fit. Apparently some models had o-rings as far as I can work out. Anyway, it wasn't leaking so it must seal. I'm not feeling confident that when this is pressed back together it will seal. Am I worrying about nothing or is some sort of sealant on the hole in the cover advisable? It does seem a strange way to do things. Just trying to avoid pulling this thing apart a second time.

Love riding this thing but my observation from my first BMW is that shaft drive is good ... until it isn't. Cheers
   

[dogshome]

There were 2 versions. As you'd expect with a bushing either side, the brake shaft wet. Then the version you have to keep the brake shaft dry.

I've had a fes of these final drives apart. The one I have now I converted from dry to wet and used the shaft that takes 4 rings and fitted technically oversize o rings.

I think the dry type was an upgrade, but I didn't like it once it was apart. Great for first (and only) assembly.

The pipe is relatively flimsy and my worry was damaging it when pressing into the full built unit.

[Barry]

My understanding was that the 78-80 models were dry i.e the final drive oil does not lubricate the brake shaft, that's how mine is.   81 On models were wet and all fitted with o rings but the number of O rings increased from 2 to 4 in an attempt to stop oil leaks.  Some previous owners may have fitted a sleeve to effectively return to the 78 - 80 arrangement in order to resolve the problem.

[gregb]

Thanks for the replies. BMW drawings seem to show the brake cam tube fitted from 3/83 on. Mine is a 2/85 model (pretty much at the end of twin shocks). I'm curious about the conversion from dry to wet shaft but can't see how it can be done with what I have. Have I misunderstood something? Photos attached here.

The tube OD is 15.8mm with a 1mm wall thickness, so it isn't a flimsy tube. The brake cam shaft is a snug fit in the tube and has two o-rings, There are more grooves so that extra 0-rings can be fitted, presumably for the earlier wet shaft. But there would be no way to fit oversize rings without putting a bush in the housing at each end, otherwise that shaft would be flopping around. So I'm thinking I'll just try to re-fit it as is and try to seal the tube in the cover.

Or put less oil in!

[Barry]

If you have pressed the tube out you should be able to see if there are any holes in it that communicate with the final drive oil. If there are no holes and I don't see any in the photo, then how can it leak oil onto the brake shoes ?

[gregb]

There are no holes in the tube. While the tube and hole on the cover don’t appear to have any scoring after being disassembled, I was just concerned some oil may find its way along that junction after being pressed together again. I’ll just give it a go and see what happens.

[dogshome]

It'll be the big seal that leaks. A coke can is a perfect fit to protect the new one when you drop it over the splines.

Don't push it in too far, it sits flush with the outside of the case, but there is no positive stop.

[dogshome]

O rings. 10x2 is standard, 9x2.5 are a good tight fit. Both 14mm O/D.

[gregb]

Cheers. O-rings not so critical with the tube version fortunately. Fingers crossed.

[Bob_Roller]

If you've never done this procedure before, here's a few tips .
There are I believe 8 bolts that secure the cover to the final drive case, there are two threaded holes in the cover at the 3 and 9 o'clock position .
Thread a bolt into each hole tighten them up and the cover will be pushed off don't pry the cover off .
First time I did this, I had problems getting the large bearing on the crown wheel shaft back into the cover put the cover out in the sun for 20 minutes and the bearing went right on .
There is a thin paper gasket between the cover and case, it only goes on one way, I put a couple of dabs of sealant on the gasket to hold it in place during reassembly .
If you have a brake cam with o-rings, lubricate the o-rings and and the metal in the cover and case where the cam goes into, also I warm up the brake cam o-rings with a heat gun to make them a bit more pliable helps prevent cutting the o-rings upon assembly .

[gregb]

Thankyou.