Parts for forks

[peteremc]

I'm posting here hoping for a quick response from someone who may know the answer to my questions. Initially posted over in Restoration logs, but looking for information quickly if possible.
I'm a novice at this but have disassembled by 1982 R65LS and got to the forks and was replacing fork seals and found that the "bumpers" that sit on the damper rod seats had completely disintegrated (see photo for how they came out of the forks).
Started to investigate, Monte helped out, but there is no indication of these parts appearing in 2 workshop manuals I have or in a number of on-line microfiche, and Chris Harris has a disassembly and reassembly of R65 forks on Youtube and these parts were not there on disassembly and were not installed in reassembly.
So, do I need purchase replacement parts or just reassemble without them?
If I need to reinstall, does anyone know what the part number is and are they freely available?
Many thanks

[Barry]

There were no bumpers on the damper rod seats nor are they needed as the seat inherently acts as a hydraulic bump stop when the tapered section of the top hat enters the valve body. This is a standard feature of most damper rod forks.

Instead the red rubber bush sits under the damper rod piston to cushion the forks at full extension - item 24 on the diagram. Most every other forks uses a topping out spring in this position.  

The rubber bushes are still available from BMW part No 2431421237215  or alternatively I used these from Motobins which fit even though they are not listed for our forks.

[peteremc]

Thanks Barry, but as a complete novice, I'm not understanding your advice.

You say there were no bumpers on the damper rod seats, so my first issue is that I don't understand what the disintegrated mess was on mine when I got them out.

Then you said the ring identified as item 24 on the parts diagram sits under the damper rod piston. When I look at the diagram, this is at the very top end of the internal fork mechanism to where I'm looking i.e. I'm at the very bottom where the damper rod seat is. I don't understand the relationship.

Maybe I'm missing something because I have not totally dismantled the forks. I've just removed the wire circlip from top of the forks and the screw at the bottom end of the damper rod so that I can separate the two parts.

Do I need to fully disassemble the forks or can I reassemble without bumpers on the damper rod seat?

Like I said ... complete novice here

Thanks

[Barry]

Thanks Barry, but as a complete novice, I'm not understanding your advice.

You say there were no bumpers on the damper rod seats, so my first issue is that I don't understand what the disintegrated mess was on mine when I got them out.

Then you said the ring identified as item 24 on the parts diagram sits under the damper rod piston. When I look at the diagram, this is at the very top end of the internal fork mechanism to where I'm looking i.e. I'm at the very bottom where the damper rod seat is. I don't understand the relationship.

Maybe I'm missing something because I have not totally dismantled the forks. I've just removed the wire circlip from top of the forks and the screw at the bottom end of the damper rod so that I can separate the two parts.

Do I need to fully disassemble the forks or can I reassemble without bumpers on the damper rod seat?

Be assured that the correct place for the one and only red rubber bush is where the diagram shows it which is directly under the damper piston.  Consider what happens when the forks reach full extension, without the bush to absorb the impact there would be metal to metal contact between the underside of the piston and the valve plate #23 which has been known to shear off the piston. As I said if you look at the internals of almost any other damper rod fork there is a short topping out spring where we have the bush.  Why BMW chose to go their own way on R65 forks I don't know because even the R80ST forks which are otherwise almost identical to ours have a spring rather than a bush.

How yours got to the bottom ?  Possibly a previous owner didn't understand the function of item 18 as the hydraulic bump stop and put it there in addition to one in it's proper place.  The other possibility is when they truly disintegrate, the bits pass through the damper holes down to the bottom ending up as a sludgy mess. Other members here will confirm that.

You might yet find a bush or the remains of one where it's supposed to be so you do need to remove the large circlip #19 at the bottom of the stanchion which will allow the valve body assembly to drop out.  

Let us know what you find, the valve body may be a little different to the diagram being a shorter 2 piece type with a spring but the topping bush should still be in the same place.

[montmil]

Perhaps this will clarify:

Note the color of the sludge at the top. Kind of red-ish. And above the valve body.

Proper install sequence. The white nylon ring fits inside the piston.

[Barry]

Let us know what you find, the valve body may be a little different to the diagram being a shorter 2 piece type with a spring but the topping bush should still be in the same place.  

Notice Monte's 2nd picture illustrates the later 2 piece sprung valve body which is different from the parts fiche diagram.  The spring will make removing and especially replacing the big circlip a little more difficult than it is with the one piece valve body and you will have to improvise something to compress the spring in order to do it.

[nhmaf]

Read this thread-
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1371526053/21#21

Chances are your 82LS may have the later spring valve assembly that my 82 LS has.    It does make reassembly of everything a bigger challenge.   I built a compressor with some 9/16" all thread, but the sheet metal I had was bent all out shape fighting the pressure of this short spring.   I finally ended up using brute force, and having a helper - to slip the locking ring in place while a leaned on a socket driver to shove the spring back - it isn't a long spring, but that sucker is stout!

[Barry]

I suspect the spring is stiffer than it needs to be. It is in fact the same part no as the topping out spring in the R80st so a parts bin expediency on BMW's part.

Peteremc,  if you are put off at the thought of removing and replacing the valve body against this spring pressure the red rubber bush will come out of the top of the stanchion if the the damper rod is also removed from the top.

[peteremc]

Thanks all.

I'm firmly on what they call the steep learning curve. In a very practical sense. Hands on.

I went in and did the full dismantle of the forks and the photo below is what came out. It seems I have the earlier model forks without the hefty spring, which I hope will make reassembly a bit easier. Strange that some ‘82 LS bikes have different fork internals, as nhmaf obviously has different ones to this.

Another thing I noticed is that the fork springs are wound uniformly i.e. I thought they were wound tighter towards the bottom of the spring and had to be replaced the way they came out, but mine have a short, tightly wound section top and bottom. Wonder if they might be after market?

Now I see what's in these forks I get that the top bumper bush has probably just disintegrated and most of it ended up sitting at the bottom, because there were bits all through the forks, top to bottom. Big chunks and little chunks everywhere.

Fortunately, the rings (like piston rings) all look in new condition. I’ve seen what those babies can cost and I didn’t budget for that. Well, the budget is blown anyway, but that’s still a relief.

Thanks for the photos, parts diagrams and links everyone!  I feel like I now know my forks very well and all this started with a simple replacement of fork seals. Also thanks for the tip on the bumper available from Motobins, Barry. I’m onto that one.

Thought I would include a photo of where I’m up to with reassembly at the end of today. Swing-arm in, nice and straight and torqued appropriately. Final drive mounted.

I would be a lot further except for the *&%$#*@!! centre stand springs. I have fought with these suckers for at least an hour to an hour and a half this afternoon. If not for this I may have the bike up on the centre stand, brakes in, and rear wheel mounted and could move on to other things. Very frustrating end to a productive weekend. If anybody has any strategy that I can use to get these damn springs in it would be appreciated. I will send beer!
Cheers

[Barry]

What you have is a half way house between the earlier and later damper valves. You have the full length damper valve body with the sprung circlip to eliminate any end play. Make sure the little tabs point up wards when you re-assemble. This eliminates the need for shimming with item 20 on the fiche diagram so don't worry that you don't have that item. Curiously you have the later thick plastic valve washer which is a good thing.

The reason for several differences in the damper valve with respect to the fiche diagram and nhmaf's pics is because BMW improved it several times in an attempt to eliminate topping out clunks. There are at least 4 different arrangements in the first 3 or 4 years of production.

Just a comment on the Motobins bush. Unlike the originals they will last for ever but at the expense of providing less resilience than the original red ones.  The red ones provide a softer cushion to the forks at full extension but don't last the distance.  

The springs sound stock. They are dual rate with 66 coils of which 7 either end are closely wound.  The springs starts off with 66 active coils to give a spring rate of 27 ftlbs then when the closely wound coils close up there are only 52 active coils which increases the spring rate to 34ftlbs. Wire diameter should be 3.5mm and is there an orange/brown paint mark on the springs ?

The trick with centre stand springs is to insert a washer or coin between each coil when they are extended. That will prevent the spring closing up and make it longer.

[georgesgiralt]

The trick to put the centre stand springs is to have the bike actually sitting ON the centre stand.
THis is when the springs  are the less extended. So easiest to fit.

[peteremc]

Now I feel like I really know my forks, thanks again all.

Those bloody springs! A couple of great tips there, so I'll get the springs and insert some coins (if my wife will actually trust me with money!) and put the bike up on the stand. I was only about 1/4" away every time I tried on the weekend so that should get me there.

Cheers

[nhmaf]

Last time I changed center stand springs I used a bunch of "recycled" flat washers from a disassembly project a while ago - you don't even need to get in between every single coil - I found with the thick washer I just needed about 15 or so to give it enough slack to make it simple to pull the remaining bit to hook into place.

Those earlier style valves make it easy-peasy to re-assemble, in comparison - count yourself lucky in that regard!   Along with BMW tweaking things at the factory to try to deal with the clunk, dealers also were given instructions on refit kits to try to deal with it - I think my bike may have had some dealer work in that regard sometime in the first 12 years of its life before it went into long term storage for years and years..

[georgesgiralt]

Hello Lads,
I just got an idea !
I looked at the fiche for an R100CS made in 1984 and saw that the fork valve body has two versions: one simple like the R65 original and one double with a spring in between like the LS NHMAF shows us.
Do you think that these parts will fit an R65 fork ?
The parts are not shown as "Ended" although some are not readily available for buying.

[peteremc]

Centre stand springs are on! Great tip. 2 minutes to insert washers. 30 seconds to fit the springs. Rear wheel ready to go on and we're off the floor!
Thanks heaps