What Do You Make of This?

[Frank_M]

Some background first. Each summer I spend at least 8 weeks at our previous residence, which is on a lake. Because several dogs accompany us and because I take along quite a few tools for annual repairs and maintenance to the place, my wife and I take two cars, and the Beemer stays back, inside a new storage shed. This past August after returning, I hopped on the R65 and started down our dirt-and gravel lane, about a third of a mile long. At the end I applied both brakes and was immediately tossed from the bike. There was no rear brake. (Previously, the brake had been solid.)

Back at the house I removed the rear wheel and discovered that oil coated everything. It appeared to me that it was leaking around the brake shoes actuating pin. I removed it and the pin looked fine, and I replaced the O-rings, then cleaned up everything. A short time later, I could tell the brake was again becoming slippery. Again I had a look and there was more oil. So then I figured it must be that the seal is leaking, except that emptying the reservoirs didn't support this much because the amounts drained out weren't much different that what's required. And we all know a little oil goes a long way.

This time I cleaned everything, every nook and cranny of the wheel and rear housing, and put the wheel back on. Since then I've ridden the bike about 500 miles over perhaps two weeks, with plenty of stop and go; and the brake is working fine.

So what I'm wondering is this: Is it possible that the 90-100 degree temperatures, perhaps higher in the storage shed, expanded the seal to a stage where it leaked? And now that the weather is significantly colder, has the seal contracted and "repaired" itself?

[MrRiden]

So what I'm wondering is this: Is it possible that the 90-100 degree temperatures, perhaps higher in the storage shed, expanded the seal to a stage where it leaked? And now that the weather is significantly colder, has the seal contracted and "repaired" itself?

 I'd be inclined to say no. The operating temperature of the rear drive would easily exceed the temperatures in your shed. I'd more likely surmise, using the WAG* method, that some contaminant / corrosion caused the leak and that you have flushed it with your through cleaning. Weird things happen to machinery in storage and self healing leaks is one confounding condition I've heard of before. I'm sure others will have more insight tho.
rich
*wild ass guess

[Ed Miller]

snip Weird things happen to machinery in storage and self healing leaks is one confounding condition I've heard of before. snip
rich
*wild ass guess

It never confounds me.  I'm always happy.

[Bob_Roller]

There's the possibility that upon installing the brake 'camshaft', , an o-ring got rolled, and leaked for a while until it moved around and sealed again.

Could be the final drive output shaft oil seal is about to give up it's job, and gave you a little advance warning.

[Frank_M]

If it is the oil seal, how much of a job is replacing it. Another airhead owner said heat has to be applied in order to remove and install the seals. Is this so?

[Semper Gumby]

Frank. What year is your bike.  If its a 79 or an 80 with the older "round" style rear drive there is a small weep hole that gets blocked inside of the drain plug.  Put a small drill bit to clean out the goo and allow your oil leak to drain without contaminating your brakes.  

[Frank_M]

Semper G, My R65 is an '82 and I don't recall seeing a weep hole in the drain plug. But I'll check anyway. I'll soon be putting her away for the winter and will remove the rear wheel once again and have a close look. Despite the rear brake working well over the recent miles, if there's a smidgen of oil, this time it may be easier to detect me where the leak is coming from. Thanks for the thought.

[Semper Gumby]

Its not there on the later final drives - just the pre Sept (?) 1980.  The weep hole wouldn't be in the drain plug but in the housing just beside of the drain plug.  When replacing those o-rings on the rear brake shaft make sure you use some type of grease on the rings.  This will help in pushing the shaft in place and allow the rings to not get cut or pushed out of position.

The only other thing I can think of is when greasing the spline on the rear wheel, put the grease or moly only on the wheel splines.  This helps keep the grease from getting pushed through the final drive seal and into the final drive.  You will know this has happened when the oil coming out of the final drive is darker than normal.  When this happends dirt also get through - not good for the final drive.  

If you can see a lot of grease deep into the splines of the final drive (near where the seal is) then clean it out.  I used a popsical stick cut in half longwise.  Don't use anything sharp or pointy unless you are very careful as the seal is at the inside end of the spline.

Good luck.