Hi!

Can`t help you to solve the mystery. But I have the same experience with this.

Have owned the same K in 25 years, which have been parked at the same spot
on the centerstand in my workshop every winter.
About 12-13 years ago it emptied almost half of the oil content in the final drive
on the floor through the breather.

This have happened only once, been scratchin` my head since........

Inge K.

 

JMHO but I think that on many of these bikes that the input seal on the FD shaft is getting old and tired.

 

Thanks guys!

It's true that everything on this bike is getting old -- just like me.

I thought about the seal in the final drive unit, but the oil "seemed" to issue from the breather hole. But that wasn't entirely certain since oil had blown around and dripped down.

Then when I took again it didn't leak at all.

Anyway, I'll be going on a 400 mile trip in two days. I will know then if the problem reoccurs.

If the final drive seal is faulty, will enough oil remain in the rear end so that it does NOT destroy itself or will it all leak out on the road?

 

Mystery oil leak

I had my bike (K100RS) on my lift in my shop and found a puddle of gear lube under the rear wheel. This was in the dead of winter. The lube came out of the breather hole on top of the FD. How or what would cause the oil to climb up to the top of the FD is beyond me. This is the second time it has happened to me. I can't think of any internal pressure inside the FD that would cause the oil to raise up and seek relief through the breather hole. Of course, if there was any pressure inside the final; drive, it would be relieved throught the breather hole. I think the damn bike is :"possessed".

 

How much oil are you putting in there? It should be to the bottom of the threads on the filler hole.

The only way gear oil should come out of that breather cap is if you drop the bike.

 

mystery leak

I measure the lube in a metric beaker and it always comes to the bottom of the threads. Of course, this has to follow a thorough draining overnight. Duck, it's one of those mysteries has has no answer other than a good clean up after a purge!!!!
BTW, remembering the last time I dropped a bike: At night, hard downpour, 4 lane road and some rectal driver pulls out a couple car lengths in front of me. I dumped my 1963 Triumph (new-cost about $1200) and slid past his rear bumper. He never stopped. I got a little skinned up but got back on the bike and proceeded home. The year was 1963.

 

I also don't have a solution to your mystery but as another possible clue I'll add my experience with fluid coming through the breather hole.

Once, when the universal joint at the front of the drive shaft broke on my k100, I reved it a bit wondering why it wasn't engaging and then saw the fluid come boiling out of the breather hole of the Final Drive. I am still not sure why this happened and can only assume that the friction on the driveshaft heated up the oil. This seems unlikely but I can't think of anything else. I replaced the driveshaft, refilled the FD and for 30k miles it has been fine.

 

Speedo sensor

Might not be the actual cause in this case but:

I just had to replace the O ring on the speedo sensor because it had a cut in it.

Strange thing is, the gear oil was not just around the sensor, but up the side of the drive and a little got forward of the mounting flange too.

Since I replaced the O ring, the drive is perfectly clean after several long rides.

I suspect the high viscosity and vibration/harmonics are causing the gear oil to migrate where I didn't expect it.

 

Hey Inge, did you ever figure out what casued the oil leak from breahter, mine did it last week, after sitting in the shop for three weeks, just boom there was oil coming out the breather.

Strange one

 

There is a bulletin on that "peculiarity" and maybe a fix in case it is constant. I can cut & paste out of it and it says something like that:

Complaint: Oil leaks from the rear drive vent on a very hot day, usually shortly after the motorcycle has been parked. The oil level is checked and found to be correct.
Reason: The day is hot, the rear drive is hot from operation, and the oil is at the top of the reardrive from the normal motion of the gear rotation. Air is below the oil, and the rear
end becomes air locked (I.E. the oil cannot return to it’s normal space).
The rear end need to breath to let the oil return to it normal space in the housing.
Note: The following remedy is only to be performed on units which have had this complaint
and you have confirmed the proper amount of rear drive oil.
Remedy: Remove the rear drive cover and with a small 3 sided file cut a grove 2mm X 2mm, in the rear drive housing as shown in the drawing on page #2. This will allow the trapped air to escape from the inter part of the rear drive, and at the same time allow the hotexpanding oil to return to the proper place. Please ensure no filings are
allowed to remain in the rear end.

Note that it is for the paralever bikes but looks like it may apply to others also from what I have seen in other places.

Anyone wants the whole thing,if just for the diagram I can't copy/paste here, just PM me but only if you are willing to either scan it and post it or have the software to do it directly from a PDF. I don't have time....my K1200RS is also seeping a little, I should check the level properly, may just be a tad too high.