Front Forks Maintenance

[Tony Smith]

Following on from Barry's post, some assemblies ended up a bit short (or the bottom of the fork leg was machined too deeply) and the maker of the forks fitted shims - if the shims are not present then the damper body (21 in the photo) can move up and down. This causes a really annoying noise and may (and I stress the word may) lead to premature failure of the circlip.

Check to see if your No.21 has any movement after fitting the circlip - if so you need to obtain shims. My memory tells me that the shims from some other BMW model fit.

BMW had two goes at this - the first attempt was to fit shims, which in my opinion is the correct way to go, their second attempt was to use a variety of circlip called a "seager" clip which has a number of raised right angled components that act to "pre-tension" No.21 so it can't move.

I think firstly that the seager clip approach is mickey mouse and secondly that they are a bastard to fit, in fact i suspect that many R65s that had them now do not because the mechanic rebuilding the forks couldn't fit them, or they flew across the workshop, never to be seen again, and were replaced by an un-shimmed circlip.

I confess that the garden next to where I work on my bikes has a seager clip somewhere within it.

[Barry]

My own forks had 20 thou end play in the damper body and no shim  so I made one to fit.  In the diagram above the shim is #20 and they are still shown in the parts fiche in various thicknesses so may be available from BMW. The story I heard about the seager circlip was it was introduced to save the assembly line workers the trouble of selecting the correct shim size. The valve body was later reduced in length and a short spring fitted above it to take up any play.

[andrewwoodhall]

..the thick plotens..
I managed successfully to remove the 10mm damper rod screw with an air impacter. Sadly, the internals reveal a broken buffer, but no sign of any additional shims, or valve washer.
The pesky  circlip was there, however, languishing in a pile of rust stained gloop.
So, I'm in the process of ringing around Motorworks/Bins, and Sherlock. No joy. Even trying BMW Park Lane....!
Any further suggestions from out there??

[andrewwoodhall]

I've placed an order with AScycles CA for the dead buffer and valve washer. Also a shim and new circlipfrom Motorworks.
I strongly suspect a less than thorough job from the previous repairer, especially as all this started yesterday, when I aimed to remedy the direction of rotation of the front wheel.
Thanks, all, for your information...

[Barry]

It's very common for the bumper bush to break up or dissolve into mush and it's the No1 thing to replace when forks are overhauled. Your BMW man can't have been familiar with R65 forks or he would have replaced it.

That looks to be the later type of circlip with spring tabs to take up any play without using shims.  Have you ordered a plain circlip and shim to replace it ? 

[MrTall100]

When I overhauled my forks recently the red buffers were mush too but unfortunately not available from Motorworks or Motobins and none in Europe according to BMW dealers.

Not discontinued though which I find amazing as really the only part that deteriorates so can’t be reused.

Would be interested to know if they actually can get hold of them.

Had to use an alternative.

[andrewwoodhall]

All cleaned up. Bush comments above noted. The end float is 10 thou. I shall see what turns up from Motorworkscirclip and shimwise.
Regards, all.

[georgesgiralt]

Hello MrTall100,
BMW is said to search for a new part maker and a new material for these bumpers. So as far as I know, the part will be available again soon ... which could take months or maybe years...
Motobins and my local BMW Guru advise to use a bushing from the /5 or /6 forks. It is made from hard plastic so won't replace the bumper perfectly but... will survive the first 100 km 

[MrTall100]

Hi George,

Thanks for the help, think that’s the one I used in the end. Motorworks had the brown one on back order since July 2017 so a year when I rang so I didn’t have much hope they would turn up in a week  .

We will see how this one get on.

[Tony Smith]

Current:
Velocette Venom 1957
BMW R65 1984

I am a former Venom owner - a mid 60s edition owned when I was young and impressionable in the 70s.

Naturally I spent a King's ransom on go-faster bits and pieces and generally got it as close to Thruxton specifications as I could.

It was like the girl in the poem "when she was good, she was very, very good, but when she was bad she was horrid".

Wish I had it now to ride on Sundays.....

[andrewwoodhall]

....so AScycles want $40 shipping to UK. But it's not in stock anyway..Start again.

[Barry]

This bumper fits from Motobins. As Georges mentioned they are not as soft as the BMW originals but on the other hand they don't disintegrate. I've had them in for over 10 years.

[andrewwoodhall]

Many thanks, Barry. What an invaluable resource this forum is.

[andrewwoodhall]

I've just disassembled  the right fork. Much tidier, but bumper bush disintegrated as predicted. Motobins/works parts arriving tomorrow, so rebuild and upandrunning by Friday....unless, of course I attack the L spider exhaust clamp nut to get at the sidestand Allen machine screw head to rebush same.... I feel a new topic coming on.

[MrTall100]

Get your blow torch out !

Saying that I soaked mine for two weeks in penetrating oil only to find them not tight at all.

Good luck