The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: arvo92 on April 06, 2014, 08:45:20 AM
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I see that the clutch thrust piston has different options and the design was changed in the middle of 1980.
One is the older version with steel piston and separate bearing inside. Second option is plastic piston with integral bearing (newer version).
Could you swap one to another or how is it done. Seems that I do not have either in my gearbox :)
I have found a diagram showing the older version. Nr 2 and 3 on the diagram showing separate bearing and separate piston. I am yet to find the diagram showing plastic piston with integral bearing.
Motorworks page has different ones for sale. Plastic looks like this: http://motorworks.co.uk/vlive/Shop/Parts.php?T=6&Q=%20CLR64167.
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That diagram above looks like the newer version. The 78-80 model has the external return spring shown below.
They are not interchangeable.
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I have exactly the assembly from the newer picture but I was totally missing the bearing. Instead the bearing has been taken away, everything put back together and clutch cable tightened to compensate for this. That explains the metal paste I could scrub off from the chamber - the retracting piston walls are quite thin now ;D
Barry - the plastic assembly is still meant for the newer clutch assembly to replace that metal piston for the 09/1980+ models. My model still counts for 1981 and therefore should be taking the newer plastic piston. I can not say I am right in this as I have never seen any plastic pistons and have not yet received mine from mail (I put the order in today) but I will confirm once I got the piston and try to assemble it.
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I've not seen what is referred to as a plastic piston in the 1981+ model year bikes. The earlier design used a radial roller/needle bearing arrangement which is generally considered inferior to the later version pictured above with the caged ball bearing. On my 1982 model year bike (built 12/81) the piston itself is metal and the end where the bearing is fitted I think is slightly different from the roller bearing one (I am not 100% sure though), so I think that switching from roller to ball bearing *might* also necessitate a change in the piston. But, the piston and bearing are separate, not integral, and not made of plastic on my 1982 model year bike. I've not seen a plastic integrated bearing part for these myself.
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I found this page:
http://www.largiader.com/articles/throwout/
The picture 81ยด through 99' shows the old clutch retracting piston next to new one.
So it might be that I answered my own question but hopefully somebody else will get help from this as well.
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I believe the two pistons are interchangeable. I prefer the aluminum one for one reason - the plastic ones tend to swell and seize up in the bore.
When the clutch starts to slip or shifts get difficult - check it out. I've had to do this before - drag the piston out of there and carefully sand it down till it slides smoothly in the bore.