Final drive mystery

[vesku]

Hi guys,

A few days before taking my '85 K100RS to winter storage I started hearing some scratching/hissing noise from the final drive. Today I finally took it out and checked. Seems to work fine, no noise and rolls smoothly. But! In and around the pinion "hole" there was odd rubbery residue, which doesn't seem to belong anywhere in there. And the smell of "burned rubber and oil" was awful! Yes, there seems to be a little oil too. Unfortunately I didn't take a photo of the pinion side but I'll attach one from the drive shaft end where you can see a little debris and oil too. Is there a seal somewhere which could have cracked? Or could this have somehow travelled from the engine end with the drive shaft? I'm planning on removing the swing arm assy and drive shaft maybe tomorrow to check but any insights appreciated!

[pdg]

Either the rubber boot between the gearbox and swingarm has collapsed and been chewed up by the shaft, or the rubber shock absorber section of the shaft itself has died... (Or it's something else entirely, like the FD unit seal or something).

Need to take it apart to see what's what.

[Inge K.]

Either the rubber boot between the gearbox and swingarm has collapsed and been chewed up by the shaft,

+1.

or the rubber shock absorber section of the shaft itself has died...

It can be seen in the picture, and looks OK.

(Or it's something else entirely, like the FD unit seal or something).

I wouldn't expect that much small rubber pieces from the seal, and not so small...but you never know.

[vesku]

Too bad I didn't have the time to check today but will next day off. Thanks guys for your input. I'm thinking the rubber boot (gaiter) is the culprit.

[vesku]

At last I had the time to complete the dismantling. The problem is a broken driveshaft. It is broke on the joint. The inside of the casing has scratches, do you think I need to replace that too?

[Inge K.]

The inside of the casing has scratches, do you think I need to replacement that too?

Shouldn't be a problem to still use the svingarm if it just some scratches, I've done it on several bikes
w/o any problem.......check the sheet metal cup that acts as a grease retainer at the swingarm bearing.

[vesku]

Ok, thx again.