R65LS:# of O-rings on brake actuating arm?

[suecanada]

Ok, I have 3 O-rings...that's on my bike, 1983, from a previous owner. Snowbum says....square grooves warrant the Orings>>>WHAT square grooves??? How many O-rings do other R65LS brake actuating arms have...maybe I am putting brand new O-rings on the wrong grooves..I did order the O-rings from Bob's BMW so they should be right thickness. But there is still a slight leak from somewhere even though my friend and Nhmaf raised the rear drive filler dome. I cleaned up all the oil to try and determine where the oil was coming from....still looks like brake right side actuating arm. Where for instance does the oil start if a inside seal is the culprit? Sitting bike...not driven.
The raising of the filler dome improved things immensely though!  [smiley=clap.gif]

[Bob_Roller]

There are several grooves on the rear brake 'camshaft', I just did two of them recently .

The square grooves are just that, they have a flat bottom to them, the other grooves are just rounded , to where a seal may not stay in place .

Unless there are different versions of this part the first and last grooves have o-rings installed in them, the others aren't deep enough for the o-rings to fit properly .

If you take a screwdriver and measure the gap between the two sides of the final drive housing, I think that most of the other grooves are nowhere near any metal to seal against .

[montmil]

It's a rather poorly engineered component. Early BMWs did not have the brake camshaft exposed to the gear oil reservoir in the final drive. These early brake camshafts rode in a solid tubular passageway that periodically required a wee bit of grease.

Guessing that BMW decided that was too much for the owners to handle so that opened up the enclosed tubular passage whereas the gear oil could sorta splash onto the camshaft and keep it lubed. The O-rings were supposed to keep the gear oil from wicking out and fouling the rear rim and tire. Good luck with that after 25-30 years of service.

I have new O-rings from Benchmark BMW in Sturgis, Mississippi. They are a weird, BMW specific size that I could not source outside of a Beemer parts vendor. Carefully installed so as not to get nicked by a sharp edge... they still weep a bit.

Be sure the crush washer is doing its thing on the "check level" bolt on the aft side of the final drive. Mine gets leaky from time to time.

Monte

[nhmaf]

I've only got the one o-ring on the brake shoe end of mine (and I actually put one on out on the outside brake lever wunder the felt washer).   There are (3) grooves in the shaft but they aren't the proper depth for an o-ring to be installed - I believe they are "guide grooves" so that one could get the shaft turned on a lathe at those locations to make the proper square bottom groove for an o-ring.   Since replacing the o-rings last year it has stopped the dribbling that it was doing, but I still cross my fingers - definitely a sub-optimal design/solution..

[suecanada]

Hmmm...I will install an O-ring on the outside under the felt washer too!!!
Can't hurt to try! Good idea nhmaf!
What I don't want to do is take on a seal replacement job, inner and outer, in the rear final drive on the off chance they are leaking. Looks from reading to be beyond me, my tools and my patience level! Probably Derek's too and he wouldn't even be in the workshop!!!

[Bob_Roller]

Taking the final drive apart for a seal replacement really isn't too daunting of a job .

About the only 'fiddly' part of the job is getting the ring gear bearing back into the final drive cover .

A good temperature differential between the two parts is the key here, get the ring gear and bearing cold put it in the freezer, or as in some parts of the world this time of year, just put it outside .

Heat the cover with a heat gun or similar appliance to 150 F., they should go together without any problems .

Also, cover the teeth of the output shaft with a heavy tape to prevent the possibility of damaging the seal as it goes over the splines .