Where to find fork piston rings

[Jbeebe]

Hi everyone, I appreciate your help in advance.

Normally i'm very resourceful but i can't seem to find repalcement piston rings for the front forks on the 1979 R65 i'm working on.

Here's what i'm looking for:

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EME has some, but they are listed for a different model than the R65. https://www.euromotoelectrics.com/produ ... ing059.htm

Any insight?

Thanks!

[SteveD]

Welcommen!

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[barryh]

The question is are the 36mm R65 stanchions with 28mm inside diameter the same as the type 247 forks ? See R65 data from BMW below.

Another issue is I recall reading that after market piston rings were problematic being a little too big resulting in excessive stiction so be careful about replacing original rings if they are OK.

On the subject of stiction, later type 247 forks had a a one piece white plastic wiper ring which was said to work better than steel piston rings and with reduced stiction. Someone has successfully machined the damper piston to accept the later type wiper.

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[barryh]

I found the data for type 247 forks and the answer is they do have the same internal dimension of 28 mm so the piston rings should be the same.

Both sets of data were taken from BMW training manuals so should be accurate.

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[Jbeebe]

Awesome! Thanks for the quick and knowledgeable replies, all! I'll order the part suggested and update the thread once the forks are all rebuilt

[barryh]

Jbeebe,

I have the exact same forks on my 79 and have been inside them many times so if you have any others issues just ask.

After you reassemble the damper valve body in the bottom of the stanchion, check for the presence of a shim and that there is no vertical play. BMW modified this assembly several times. The first step was a to add a shim #20 between the circlip #19 and the damper valve body to eliminate play. Mine was something like 20 thou but they are available in several sizes.

BTW it might be an illusion but the rings in your photo look odd as if the top two rings might be interwoven with each other. The rings should be stacked one over another but quite separate with each ring free to rotate. You can set the gaps 120 deg apart on installation but they are unlikely to stay that way in use.

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