Rubber into the fork

[georgesgiralt]

Hello !
Last April I put my '82 R65 back on the road. The first goal was to remove the RT fairing I bought with the bike when the bike was new.
I then dismantled the fork and cleaned all the gunk it has. And remove the two stubs above the springs. (I was told they where fitted to compensate for the fairing's weight). Then I put the mandatory 190 cc Belray 5W oil.
Lastly, the fork became noisy so I decided to dismantle it to see.
First, the oil was black and seems to have some very thin metal particles in it. Then, the rubber (item #24 in the exploded parts view) is brittle and open on one side and totally destroyed on the other side (it has slit in very small rectangular bits and they clogged every hole they can find). I had not replaced them last April as they where sound.
My nearest dealer had the red rubber available, so I've re-assembled the fork but I wonder what was the cause for this fast deterioration ?
Is it possible there is some unfortunate effect of the oil ?
Thanks for your help !

[Barry]

If those were the original black topping out bushes they do become very hard and brittle with age.  I replaced mine because there was no resilience left in them and they would no longer function to cushion the forks at full extension. They get a pounding every time the forks top out which is just as likely to have destroyed them as the new oil.

[georgesgiralt]

Actually they where changed at some point in the life of the bike.
Maybe last time I changed the seals. Can't remember and can't find the dealer's invoice...

[montmil]

Actually they where changed at some point in the life of the bike.
Maybe last time I changed the seals. Can't remember and can't find the dealer's invoice...

Senior Moment, eh?

[georgesgiralt]

Well, considering she  sat unused since 98, and this was not a so important repair, I do not consider myself too senior, even if y memory is very far from what it was...
I was surprised looking at the Chris Harris video to find that my springs are different from the one show in the video. Mine have the same serrated coils at both ends, so one can't tell which side to put first in... Maybe they were exchanged when they fitted the RT fairing ? As this was 30 years ago, I can't ask anybody...
I ran the bike today and found the fork to behave much better. Maybe the 10W oil is too much. But this is easy to change. I'm much more concerned by it's inability to go to the red line. I think I've some problems with one or the two spark plugs cap. (I can't fire the timing light on the right cylinder wire... ). So something to check tomorrow...

[Barry]

Stock BMW springs are dual rated with close wound coils at both ends so it doesn't matter which way up they go.

The video must have used aftermarket springs.