oily brakes

[timbo]

Hi
im getting oil leaking into my rear drum, im assuming the most likely cause is a shot bevel drive gasket, in the manual it says you need to apply heat to remove the cover , is this really neccesary, also there appeared to be a lot of oil around the pivot pin ,could it be leaking there.
thanks in advance for any advice
cheers
Tim

[Barry]

Depending on year of bike it could very well be leaking from the brake cam shaft.  Not on 78 -80 models but quite possible on later years where there will be a varying number of O ring seal fitted to the shaft. BMW increased the number of O rings in an attempt to cure leaks.

[timbo]

Thanks Barry
There was a lot of oil around the brake cam, it a 82 bike and the shaft had 3 O rings  on it , where there seems to be provision for 5, although the 2 on the drum side where fitted, will order the parts today & try that first
Thanks again
Tim

[Luca]

in the manual it says you need to apply heat to remove the cover , is this really neccesary

You need the heat to get the big bearing out of the final drive cover, and to get it back in without damaging it.

The o-rings only go in the square section grooves of the brake cam.

I never measured the groove depth in my cam, but new BMW o-rings failed within a year.  I ordered a 1 piece BMW bushing, but it was about .007" too small to press fit, so somebody made a bushing for me.  The brass bushings tap right out of the cover and FD.

I put the brake cam with the washer into the bushing so I could tap on that and not damage the new bushing.  Tapped it into the FD and then tapped the cover on to that.  The outside of the bushing is sealed with loctite (in this case just regular blue threadlocker since that's what was handy). My bushing is shouldered in the middle because it was starting to wobble in the lathe... ideally it should have a uniform OD

I put a new cover gasket and output seal in when I had the cover removed... hopefully I won't need to go back in there for a long time.  The oily brakes were becoming a real pain in the rear end  

[steve hawkins]

My R100 is suffering from the same thing again.  I will check my vent, but it looks like I am going to reduce the amount of oil in the drive to that of the older smooth variety.  just to gibe me some thinking time.

[Barry]

I could have sworn that as well as increasing the number of O rings BMW also recommended reducing the oil level but I can't find the reference and I noticed it wasn't mentioned on the service bulletin. I did find this from a well respected source and there is a general view that a little less oil in the final drive would do no harm at all.

Having a through sleeve is the real fix and what BMW should have done in the first place. Not sure if all post 81 models have the brass sleeve which makes that mod possible.

[timbo]

thanks for the pics of the sleeve , as i carnt see myself getting rid of this bike im going to have to think of something similar myself, i dont suppose anybody is manufacturing the bush. ive looked at my bike & it seems to have a bronze insert in the bevel gear housing but not one in the cover, but i havnt taken it off & looked properly
cheers

[Luca]

I should say that many people have simply fixed this problem by replacing the brake cam o-rings.  In my case that didn't work, so I a went for a (hopefully) permanent fix by going to a better design.

You won't be able to see the brass bushing in the FD cover until you remove the brake cam and washer.

The brass bushings in my final drive varied in size, so we turned the OD of the new piece to a number in between the two OD's of the brass bushings.  I'm not sure about BMW's tolerances for the brake cam bushings, but it they were hand fitted it might be possible that some of of the small bushings won't make a good interference fit in larger holes.

It wouldn't hurt to call up some machine shops and get a rough idea on the price of a one piece sleeve if you decide to go that route.  You should be able to get some rough dimensions without removing the brass bushings.

FYI, the ring of loctite around my new sleeve in the pic is squeeze-out; the sleeve was liberally coated prior to installation.

[davidpdx]

Tim,
     This was one of the first jobs that I did on my R65. Not sure why it worked because the old O-rings looked fine but as I was installing new brake shoes, I didn't want to risk getting them soaked like the worn out ones were. 6500 miles later and so far no more oil in the brake drum (knock on wood). Good luck.

[timbo]

just replaced the O rings and topped up with a little less oil, all seems ok ,i guess ill find out over the next couple of days, but havnt replaced the shoes yet just in case. l looked at the bevel case & cover again & definatly only have the bronze bush in the bevel case ,in the bevel cover there is only alli
cheers again
Tim