Boxerworks.com

If I understand your system. Pull the brake arm off the shaft marking it's position before removal. You might want to take a good picture of the shaft before sliding shaft out, IIRR the flats where the shoes ride is installed a certain flat up?? You may need to use light taps with a hammer. There should be 2 or 4 O rings on the shaft. IIRR they are 10 X 2 mm.

Inside the rear dive where the brake shaft runs through, the shaft on some models was exposed to the gear oil. Latter versions used a solid tube through there. If you have the solid tube style, it might be possible for the tube to leak??

Tom

Thanx Tom. I quess I need to take it all apart. Can't find any good pictures to see how it's constructed. Or to be able to tell if the brake pivot shaft is exposed to the rear drive oil. I don't want to order all the gaskets and seals until I find out what I need. But I may have to.

Zombie Master wrote: ↑Sat Jul 02, 2022 12:06 pm Or to be able to tell if the brake pivot shaft is exposed to the rear drive oil.

Prior to 81 (smooth rear drive casing) it isn't.

After 81 (ribbed rear dive casing) it is exposed to the rear drive oil and that was problematic with the number of O rings being increased in an attempt to cure the leaks. At some later point the bore may have been sleeved as the only certain cure.

If the oil looks like it's coming from the pivoting shaft, it probably is. The pivoting shaft is easy enough to remove. Wheel off, remove brake shoes, remove rod from brake pedal at the lever, remove lever and slide pivot out. No rear drive disassembly needed.

Look through the hole for the pivoting pin, if it looks like a solid tube great, if it looks like a gap in the middle, not as great but your still OK.

Install new O rings and see how it does in a few days or so depending on how bad a leak you originally had. If you have the full tube style hole and it still leaks, you need to seal the tube to the rear drive. I do not know how to do that. Maybe someone here can help with that.

Good luck!
Tom

Very helpful! Since I can't find an exploded pic of the 1984 rear drive. I guess I'll drain the drive, and pull our the brake pivot shaft in order to see how many O rings there are. Dealer told me there was just one.

This is Bobs list of R bikes. Pick your correct model:
https://www.bobsbmw.com/store/microfich ... eries.aspx

Some examples:

https://www.bobsbmw.com/store/microfich ... ne=33_0621

https://www.bobsbmw.com/store/microfich ... GroupID=34

I may have been wrong on the O rings. You may have a seal and ONE O ring. I thought you may have 2 or 4 O rings and NO seal.

Tom

Zombie Master wrote: ↑Sat Jul 02, 2022 6:14 pm Very helpful! Since I can't find an exploded pic of the 1984 rear drive. I guess I'll drain the drive, and pull our the brake pivot shaft in order to see how many O rings there are. Dealer told me there was just one.

This may give you an insight,it was written by an airhead dealer/mechanic of the day.

Thanx Barry, this gives me more insight. Think I'll stop by the dealer and grab some O rings. I guess a careful checking of the drive shaft oil is in order in case the leak was caused by a extra high level in the drive.

ZM -
Your near 40 year old rear drive has relatively low mileage, I suspect that it hasn't been messed with, and I suspect it never leaked until recently.

My advice:
Pull out the brake pivot shaft and replace any seals/washers with new ones exactly as they were.
Replace the large spline/flange seal as preventive maintenance.
Leave the paper gasket alone, just check that all the bolts are properly torqued.
That should do you for another 40 years.

PS -
A bit less oil (20cc!?) in the final drive may quell a leak if the bike is stationary, like in a museum.
If it's being ridden regularly, it won't make a difference, it'll still leak if the seals are bad.