1978 R100RS Fork lowers query

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Ade B
Posts: 56
Joined: Tue Jul 15, 2025 9:08 am

1978 R100RS Fork lowers query

Post by Ade B »

Doing some homework on the forks at the moment as I've a weeping LH seal which needs attention. I've no idea on the state of the fork internals, there doesn't appear anything 'off' in the handling but I've nothing to compare it to - Based on recent experience with the bike I'm expecting to reveal some horrors and what appears to be a straightforward seal and fluid replacement will end up with the entire front of the bike in bits..

Having watched a couple of vids and studied the Haynes manual, I may be missing something but I appear to have differing fork lowers. I'm about to start dousing with penetrating oil in advance of next weekend's anticipated dismantling.

Left hand fork leg is missing a rubber cap but appears look like what I expect.
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Right hand fork leg seems to missing something...
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Would welcome thoughts before I wade in and start rounding off nuts/bolt heads...

Cheers Ade.
Rob Frankham
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Re: 1978 R100RS Fork lowers query

Post by Rob Frankham »

Interesting... never seen one like that before...

FWIW, the BMW parts lists say that the bottom plug is common for all machines from 1974 (/6) to 1980 on both left and right sliders. Later forks don't have that type of plug at all. Not sure about the /5... i's a different part number but I have no other details.

Rob
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melville
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Joined: Tue Aug 03, 2010 8:32 am

Re: 1978 R100RS Fork lowers query

Post by melville »

Indeed, a curious one. I've got five different forks from 1975 to 1979 here at the house and they're all consistent with your left side.
Call me Mel. Some years ago- never mind how long precisely- having little or no money in my purse, and nothing particular to interest me at home, I thought I would ride about a little and see the other parts of the world.
Ade B
Posts: 56
Joined: Tue Jul 15, 2025 9:08 am

Re: 1978 R100RS Fork lowers query

Post by Ade B »

It appears I have a rare limited edition bike.

More valuable surely 🤣
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