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Does my damper rod assembly seem odd to you?
06/17/13 at 22:27:32
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OK, it was a long story which I will not get in to at the moment, but I had to replace the leaking fork seal to pass annual safety inspection this month in the R65LS.   I bought new seals and drain washers.  While I was in there I decided to look at the damper assembly as the ride had been different this spring - more than what I would attribute to a leaky seal.

As might be expected, the (formerly black) stop ring was disintegrated into bits.   But, I thought I recalled there also beingsome o-ring types of thingsin the channel of the piston assembly at the top.   Furthermore, this R65LS has a spring assembly (which is in (3) pieces) instead of what is generally shown as a single valve body from the old fiche - this seems like the replacement part 31422301885.. 



So, I guess my main concern as I prepare to order more parts to get things working properly again, is are there other plastic rubber bits missing in this picture besides the disintegrated black plastic/rubber top bushing that I am assuming goes between the (2) piston rings to the right of the piston base and to the left of the perforated disk?

  

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georgesgiralt
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Re: Does my damper rod assembly seem odd to you?
Reply #1 - 06/17/13 at 23:30:33
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Hello
The two rings on the left should go into the ring holder on the left. (I recall they where 3 of them on my fork ?) Then the new rubber, then the perforated disc, then the white plastic bushing then the lower seat.
On my forks, that's it. You have a spring and another seat. They do not show on RealOem. So I'm puzzled.
What kind of modification your fork had  ?
  
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Re: Does my damper rod assembly seem odd to you?
Reply #2 - 06/18/13 at 03:19:26
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Looks fine to me. You have the later sprung valve body which is supposed to be a good thing.

As Georges said you have to put the piston rings back in and 3 is the correct number. Don't put in new piston  rings unless they are broken as new ones are reckoned to be rubbish. Otherwise only the rubber bump stop is missing above the valve plate.  Can't see in the photo but if the the plastic valve washer has a beveled edge that goes to the top facing the perforated plate.
  

Barry Cheshire, England 79 R45
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georgesgiralt
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Re: Does my damper rod assembly seem odd to you?
Reply #3 - 06/18/13 at 03:44:26
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Hello !
Does any body have the part number for the valve body with spring ? Even if I select the latest R65, I can't find them on RealOem.
Thanks.
  
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Re: Does my damper rod assembly seem odd to you?
Reply #4 - 06/18/13 at 08:01:27
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Georges

Part numbers are here but the valve body is shown as ended.

This has recently been discussed on the airheads list


http://www.realoem.com/bmw/showparts.do?model=0425&mospid=51641&btnr=31_0316&hg=...
  

Barry Cheshire, England 79 R45
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Re: Does my damper rod assembly seem odd to you?
Reply #5 - 06/18/13 at 08:32:18
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OK. The fiche you show is for an R100. I always thought the forks of the R65 where different.
And if I'm not mistaken, they are somewhat because the travel is different.
This is the reason why I asked  Cheesy
  
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Re: Does my damper rod assembly seem odd to you?
Reply #6 - 06/18/13 at 09:11:49
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The forks are not exactly the same but they are the same basic type with the same stanchion diameter so I believe the valve body will be the same.


I'll have a look at the other fiche sites to see if there is an R65 specific part.
  

Barry Cheshire, England 79 R45
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Re: Does my damper rod assembly seem odd to you?
Reply #7 - 06/18/13 at 09:17:14
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Thank you both - I was careful in withdrawing the assembly from the fork tube but the rings had dislodged themselves from the piston as shown - probably due to all the bits of broken rubber getting caught up in there.

I've doen a bit more reasearch and found the BMW did experiment with the damper rod assembly, piston, and added spacers at the bottom between the valve body and the circlip on the end which keeps it all in the tube.   They were trying to stop the clicking and clanking noises that the forks were notorious for.   The R65 and R80ST forks also received some of these changes as they changed things several times between model years 1980 and 1983.   Presumably by 1985 they had standardized on the assembly using the (3) piece spring valve part as shown in the pictures, but now both the original piece, and the replacement piece, are No Longer Available.   So, treat yours with care, whichever version you have!!!

What makes things even more confusing is that the BMW microfiche drawings often show either the original parts stack up but not the later ones, or they show the all the parts - both old and new- together in the same drawing.   Since one doesn't venture into the damper rod area very often, it only serves to confuse one even more when looking up the parts in the drawings which do not matchup with what is installed. 

The (3) piston rings I've got seem to be OK - I've also read on Snowbum's website that the originals are better provided that they aren't broken, so I'll just carefully clean off the broken rubber bits and  re-use them.   Now back to the dealers to see if I can get some new rubber bumper rings...

Thank you for your help!
Mike
  

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Re: Does my damper rod assembly seem odd to you?
Reply #8 - 06/18/13 at 12:05:57
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I changed the rubber bumper a few month back (less than 6) and they were available from BMW. they were red in colour and supple.
So I think it's still the case !
  
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Re: Does my damper rod assembly seem odd to you?
Reply #9 - 06/18/13 at 12:09:11
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georgesgiralt wrote on 06/18/13 at 08:32:18:
OK. The fiche you show is for an R100. I always thought the forks of the R65 where different.
And if I'm not mistaken, they are somewhat because the travel is different.
This is the reason why I askedCheesy



The R100 part number I suggested is correct.  Although the R65 diagrams don't show the alternative valve housing it is in the parts list below although still unavailable unless you are lucky enough to find one in stock somewhere.

http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51892&rnd=04302013

  

Valve_housing.png ( 4 KB | Downloads )
Valve_housing.png

Barry Cheshire, England 79 R45
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Re: Does my damper rod assembly seem odd to you?
Reply #10 - 06/18/13 at 12:36:33
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Barry,
I've phoned my nearest dealer. None available, either at the factory store nor in any French dealer...
So my fork will stay with it's noise, clung and clank.... 30 years that I live with it.  Roll Eyes
  
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Re: Does my damper rod assembly seem odd to you?
Reply #11 - 06/18/13 at 13:54:42
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You don't need to live with as it can all but be eliminated by other means.

If the clonk is experienced when riding off the edge of kerbs or into pot holes then I believe it due to the forks topping out at full extension.

With only the inadequate rubber bump stop to cushion the clonk I assume the spring loaded  valve housing helped absorb the shock in the same way topping out springs do on almost every other fork. In fact if you check the part numbers the valve housing spring is identical to the topping out springs on other BMW forks. We can't fit them retrospectively as topping out springs would lower the ride height on our forks because the damper rod is too short.

There is another way. By increasing the rebound damping. The test that you have it right is to remove the wheel and fork brace and fender so that the legs can be stroked by hand independently. With the spring out you should be able to feel that rebound damping is stiffer than compression and most important for curing the clonk, there should be a significant increase in damping over last 20 - 25mm of travel before full extension. This is due to the rebound orifice falling below the valve washer so that the only path for the oil is leakage past the washer.

Problem is you can't increase rebound damping with much thicker oil as although that will help, the increase in compression damping will spoil the ride.

You can increase rebound damping over the last bit of travel more or less independently of compression damping by reducing the leakage past the valve washer. And you do that by reducing the clearance between the valve washer and damper rod. In fact the modified sprung valve housing also incorporated a thicker valve washer with this reduced clearance.

(Mike, if you still have your forks in bits any chance you could measure the damper rod diameter and the valve washer hole diameter)

It's only taken me 5 years and many trial to get it almost right but it can be done.
  

Barry Cheshire, England 79 R45
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Re: Does my damper rod assembly seem odd to you?
Reply #12 - 06/18/13 at 14:00:01
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Barry, could you please stop speaking Chinese to me ?
I've lost my universal translator (Men In Black) so I'm puzzled at best  Embarrassed
The funny thing is that I had to replace the rubber ring (last time I changed oil I got small speck of hard translucent rubber in the oil, I think I told the forum about it). Since that time, the left leg make a different noise and it change with the temperature or the humidity ... or ....  At first I thought I forgot to torque some part or the triple clamp. Then I thought the 3 rings where not installed properly, then I decided to use the bike and let it sit until next oil change... and see what comes out.
  
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Re: Does my damper rod assembly seem odd to you?
Reply #13 - 06/18/13 at 14:10:22
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Ok here's a simple mod.  


Buy the new valve washers and machine the recess in your existing valve bodies to the same depth as the unavailable part.

Mike, any chance you could also measure  the valve body washer recess and the washer thickness.
  

Barry Cheshire, England 79 R45
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Re: Does my damper rod assembly seem odd to you?
Reply #14 - 06/18/13 at 22:01:57
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I had to do a bit of actual client work today, but should have some time to take measurements on Wednesday and report back here.

BMW shows various shims of very slightly different thicknesses which they initially specified to be placed under the (original, 1-piece) valve body, as they anticipated that part of the clunk was caused by excess clearance/end play in the damper assembly as parts wore-in or spring strength diminished.   These were only slightly successful, and the "final" accepted solution was apparently the split, 2-piece valve body with the spring in between, and apparently some changes in the rubber ring and alterations to some of the orifices in the damper rod.   I will say that my forks did sometimes "clunk" when they came to full extension, but we will see if it really stops with new replacement rubbers.

I tell you that short spring in the split valve design is pretty darn stout -
  

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Re: Does my damper rod assembly seem odd to you?
Reply #15 - 06/19/13 at 22:16:05
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OK, I have some measurements - be aware that there might be some wear involved, and my garage lighting isn't quite as good as I'd like it to be.   I used a set of dial calipers which I also use for reloading ammunition, so all measurements are in units of inches, to the thousandths place:

Damper Rod Diameter (External, checked 3 places) 0.630 Inch

Valve washer (white plastic washer)
Thickness: 0.155 Inch
Inside Diameter: 0.635 Inch
Outside Diameter: 0.945 Inch

Valve body (top half):
Inside diameter: 0.785 Inch
Valve washer recess Depth: 0.170 Inch  (Yes, the recess is just slightly deeper than the thickness of the white plastic washer)

The "drilled washer" with the (8) holes in its body:
Inside diameter: 0.700 Inch
Outside diameter: 1.172 Inch (external edge has uneven ridge, possibly from wear?)
Thickness: 0.082 Inch
Hole diameter (approx): 0.115 Inch x 8 PLACES
Drilled holes are centered about the center of the "washer", with opposite drilled hole centers 0.900 Inch apart.   So, when the drilled washer is in contact with the white plastic valve washer (and I can verify this from bright wear marks on the metal washer, the white plastic valve washer covers approximately 50%-60% of the area of the (8) drilled holes. (.ie, the holes are slightly more than half blocked off).

The damper rod has QTY (1) 0.110 Inch DIA hole drilled through its tube from outside to inside (but not out the opposite side) centered about 1.010 Inch below the bottom of the piston with the piston fixed to the rod/tube.   The damper rod has QTY (2) 0.180 Inch DIA holes (drilled through and through) located approximately 1.300 Inch from the bottom end of the rod/tube (the part which sit into the base support).


My rubber rings, new plastic valve washers, and new drilled wasahers should be available for me to pick up at MAX BMW on Thursday, so I will start to put things back together - let me know if you need anything else measured before it is too late!!
Cheesy
  

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Re: Does my damper rod assembly seem odd to you?
Reply #16 - 06/20/13 at 02:20:43
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Mike, 

Thanks, that's brilliant,  I'll knock out some drawings comparing old and new valve body assemblies when I get chance.  In the long run it's going to be important to have the dimensions of parts that are no longer available.
  

Barry Cheshire, England 79 R45
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Re: Does my damper rod assembly seem odd to you?
Reply #17 - 06/22/13 at 16:00:44
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Using the data that Mike provided I've done a comparison between the original damper valve body components and the revised items.

The valve washer has been increased in thickness and the clearance between the washer and the damper rod reduced The vertical movement of the valve washer within the valve body recess has been reduced to half of the previous amount.


Comment:

This is all as expected. The reduction in clearance between the valve washer and stanchion will reduce oil leakage past the washer and increase rebound damping particularly over the last inch of travel. This was done to provided a stronger hydraulic bump stop effect in order to try and eliminate topping out clonks.

The vertical travel of the washer is reduced by half. The washer moves up under fork compression allowing a relatively free flow of oil through the valve plate holes and down under rebound sealing against the valve body.  In the transition between compression and rebound there is a dead band while the washer is moving so the new reduced amount of travel will improve damping control.

The only surprise was the lack of a beveled edge to the top surface of the valve washer. Mike mentioned that approx. half of the area of the valve plate holes are covered when the valve washer is in the up position (forks under compression).  The service bulletin shows a beveled edge which would uncover some of that lost area improving oil flow through the valve plate.


Detail dimensions in mm with old original items in brackets.

Valve washer white plastic  (steel)
Thickness: 3.94   (1.48)
Inside Diameter: 16.13  (16.2)
Outside Diameter: 24     (24)

Valve body
Inside diameter:  19.94  (19.94)
Valve washer recess Depth: 4.55  (2.45)


There were no changes to the damper rod or valve plate dimensions.
  

Barry Cheshire, England 79 R45
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Re: Does my damper rod assembly seem odd to you?
Reply #18 - 06/22/13 at 16:50:08
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Hope an administrator will add this thread to the FAQs Section. Very valuable information presented herein.
  

Monte Miller
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Does my damper rod assembly seem odd to you?
Reply #19 - 06/22/13 at 17:13:06
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This Topic was moved here from BMW Technical Q&A, Primarily R65 [move by] Bob_Roller.
  

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Re: Does my damper rod assembly seem odd to you?
Reply #20 - 06/22/13 at 20:10:43
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I've taken some more measurements and will create some sort of drawing or update for Barry with the additional data -

I noted the bevel edge description in numerous sources, and, I thought that I could JUST barely detect a slight difference in edges of the valve washer on the used part that I took out, but the new valve washer that I bought I stared at for quite some time and couldn't detect a difference from one side or the other on either outer edge or inner edge.   I bought new bumper rings, valve washers, "drilled washer", and new piston rings.    I used the new parts with the exception of the new piston rings, which I might possibly return to MAX, but I wanted them handy in case I encountered a damaged ring, which I did not, and they appear to be still in good shape.

I've taken some more photos and will upload a PDF linked to this topic for posterity.

At the moment I cannot provide a ride report/update as something *ELSE* seems to have now failed on the bike - I suspect the 3 year old battery has died despite being left on battery tender over the winter.  The bike ran perfectly on my trip down to MAX BMW a couple weeks ago (round trip about 90 miles).  Since then it has just been on the lift, with wheels and forks off while I've been repainting the wheels, putting new tires on, replacing the forks seals and rebuilding the damper units, and adding fork gaiters.   Now that I've buttoned it all up for its shakedown cruise, it won't turn over.   At rest with ignition off, battery voltage reads 12.8V, but as soon as I turn the key on, the voltage drops to about 6V.  I'm checking for shorts, too.  Though I cannot imagine that I've pinched any wires anywhere -  Grrrrrrr.
  

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Re: Does my damper rod assembly seem odd to you?
Reply #21 - 07/07/13 at 14:23:06
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I will be doing a more thorough write up and appending to a thread in the FAQ section in a while, but thought I'd at least post up some pics here to show closure and provide breadcrumbs to anyone else in need of rebuilding their damper rod assemblies in the fork tubes.

this covers the "later" style R65 forks which have the (3) piece (includes a very stout spring) damper valve assembly.

Generally speaking, if you remove the sliders/lowers from the fork as part of replacing a leaking fork seal, just slide out the damper rod assembly base from the end of the fork tube and look for the telltale black "gunk" of plastic bits that signifies a disintegrated black plastic topping out bumper/bush inside the damper assembly within the fork tube:

Ugh!

OK, these are the parts you will need (or at least can buy, as some are No longer available) for rebuilding the damper rod assembly:


*IF* you are careful when removing the damper rod assembly, you *may* not need to get new wiper rings for the damper rod piston (those tiny piston ring things in the upper right corner of the picture) as they usually don't wear out, but can become damaged, bent, mangled, etc. upon either removal or re-installation, or if you've just been unlucky.   These are the most expensive parts of the rebuild list - they are almost $8 a piece and you need (3) for each piston (one in each fork tube)


This is what the re-assembled damper piston assembly would like like with replacement topping out bumper (red plastic ring which replaces the previously missing/disintegrated black platic ring in the first pic in this thread). and new valve washer (white plastic ring) and drilled washer (metal disk with 8 drilled holes in its outer edge).   I was fortunate and could re-use my original piston rings, though I did carefull clean everything and inspect for damage prior to assembly.


The "official" writeup will include more info, plus tips on how to get the $%^&@! thing back into its tube and compressing that @#$% spring!  

hope this helps!
Mike
  

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