Unknown rattle/clunk near headlight/handlebar

[quixotic]

I was just wondering, if a previous owner had installed after market springs .

I installed a set of Progressive springs in my '81 R65 and they were about 1 inch, 25 mm shorter than the stock springs .

PVC spacers were included with the springs, to take up the difference in the shorter length replacement springs .

I'm not sure, but the springs in mine had the top half dozen and the bottom half dozen spirals side by side (ie, almost fused).  Looks like they came out of the factory like that.

[quixotic]

If the heavier oil doesn't eliminate the topping out clunk then the only option is to use some other way to increase rebound damping ideally independently of compression damping. One method is to reduce the clearance between the valve washer and damper rod.  

If you get to that stage I have some dimensions for making a new washer.

I think I'm at that stage.

[Barry]

When you tested the rebound damping did you feel the increase as the forks approached full travel ?  If not you need to accurately measure the clearance between the damper rod and valve washer hole. My original steel washers had 0.25mm clearance (0.010")  The area that represents is 12.7mm² which is almost twice the area of the rebound hole proper at 6.8mm². I made up new nylon washers with 0.15mm clearance that reduced the leakage area to 7.6mm² I also increased the washer thickness from 1.48mm to 1.95mm and bevelled the top edge. All of these changes mimic the later valve washers that BMW introduced except that washer was thicker still and used a different valve body with a deeper recess.  

Get the valve washer leakage right and you will feel the hydraulic bump stop effect on the last bit of rebound damping and that will completely eliminate the topping out clunk.

[quixotic]

When you tested the rebound damping did you feel the increase as the forks approached full travel ?

I felt something that may have slowed down the rebound slightly, but it didn't really feel like a gradual hydraulic damping.  More like a muffled click.  

But I don't think that the clunk/rattle noise appears only when the forks are fully extended.   Seems like it appears even on relatively minor bumps at fairly low speeds.  

Snowbum mentions the following for post-81 bikes:

Another part of this bulletin was for fork spring rattling inside the fork tube. There was supposed to be a white nylon plastic spacer used on BOTH ENDS of the spring.  Implied was that if one or both were missing, they were to be installed.  

I almost suspect that this type of movement describes the sound I'm hearing.

[quixotic]

Wow.  Elsewhere, this issue started a 6 year long thread:

http://www.advrider.com/forums/showthread.php?t=379398

I kind of like the advice in post # 51 (too much oil).  At least it's easy to check.  

[Bob_Roller]

Probably explains this part in the parts diagram, but no part number available .

Reference item # 18 .

http://www.realoem.com/bmw/showparts.do?model=0364&mospid=51897&btnr=31_0296&hg=31&fg=42

[quixotic]

I made up new nylon washers with 0.15mm clearance that reduced the leakage area to 7.6mm² I also increased the washer thickness from 1.48mm to 1.95mm and bevelled the top edge.

That kind of precision is beyond my capabilities.  Have you ever thought of making these and selling them?  I, for one, would pay some big bucks for them.   Or would the diameters of the damper rods change a bit from bike to bike?

[Barry]

I felt something that may have slowed down the rebound slightly, but it didn't really feel like a gradual hydraulic damping.More like a muffled click.
But I don't think that the clunk/rattle noise appears only when the forks are fully extended. Seems like it appears even on relatively minor bumps at fairly low speeds.  

That  information about the noise raises another possibility. The valve body is retained in the stanchion by a large circlip. On the very early forks there was no attempt to shim the valve body to prevent any vertical movement so the valve body could rattle up an down by a small amount. Several mods were done first to shim the valve body and later to spring load it.  You need to measure how much play there is betyween  the valve body and the circlip then  select a shim to fit. You will see the shims listed in the parts fiche. Mine had 0.020" clearance so I made a shim to fit.

Snowbum mentions the following for post-81 bikes:
Another part of this bulletin was for fork spring rattling inside the fork tube. There was supposed to be a white nylon plastic spacer used on BOTH ENDS of the spring.Implied was that if one or both were missing, they were to be installed.  
I almost suspect that this type of movement describes the sound I'm hearing.
 

That’s not applicable to our  bikes. There are no plastic spacers for our springs. Be careful about advice based on other models of airhead forks because they are different. In the ADVrider thread for example even some of the  knowledgeable guys will have no experience R65 forks specifically. Glad you liked post  #51 though because that's me.  

There is another other option which is to replace the whole damper valve assembly with the later type that has the thicker modified washer. This is supposed to address both the valve body rattle and the valve washer leakage issue I couldn't find those parts in the UK but I believe they are available in North America. If you look at the online parts fiche you will see a change of valve housing and washer listed from 09/80.

[quixotic]

That  information about the noise raises another possibility. The valve body is retained in the stanchion by a large circlip. On the very early forks there was no attempt to shim the valve body to prevent any vertical movement so the valve body could rattle up an down by a small amount. Several mods were done first to shim the valve body and later to spring load it.  You need to measure how much play there is betyween  the valve body and the circlip then  select a shim to fit. You will see the shims listed in the parts fiche. Mine had 0.020" clearance so I made a shim to fit.

I think I'll try that.  They're dirt cheap, so I'll probably get a good assortment (if Shail's has them in stock) to deal with whatever gap I encounter when I open the forks up again.  

There is another other option which is to replace the whole damper valve assembly with the later type that has the thicker modified washer. This is supposed to address both the valve body rattle and the valve washer leakage issue I couldn't find those parts in the UK but I believe they are available in North America. If you look at the online parts fiche you will see a change of valve housing and washer listed from 09/80.

I see the U.S. stock on the valve housing has "ended", so I guess I won't be ordering that.  

I'll probably also go from 7.5 weight to 10 weight oil.  And maybe I'll try your #51 suggestion, too.

Thanks.  

[Barry]

I'll probably also go from 7.5 weight to 10 weight oil.And maybe I'll try your #51 suggestion, too.

I don't how you are measuring oil volume but I always do it with a dipstick. The spec. is 35mm + or - 15mm above the damper piston top. So between 20mm and 50mm. I find the difference that range makes is very noticeable and run towards the lower end at 25mm.  You should experiment to see what works best.

[quixotic]

Shails doesn't have any shims in stock, and it sounded like they haven't had them in decades...if ever.  So I was wondering if I could make my own out of brass.  Lee Valley sells sheets of "half hard brass, which resists compression" in thicknesses ranging from 0.001" to 0.01".  Is the shim area an area which takes the full weight of a compressed spring?  And is it critical to get the inner and outer diameters of a shim precisely cut?  (I guess even after having taken a fork fully apart, I still don't really understand the dynamics of the whole, and the functions of the parts).  

Also, is the function of the shim to ensure that there is no space between the valve housing and the perforated washer, as well as between the valve housing and the circlip?  

[Barry]

Is the shim area an area which takes the full weight of a compressed spring?And is it critical to get the inner and outer diameters of a shim precisely cut?  

The only time the shim would take the weight of the compression spring is when the forks are at full extension. I think brass would be fine. The dimensions should be exactly the same inner and outer diameter as the valve body. Don't make the mistake I made of making the inner diameter too small thinking it didn't matter as when you look at how the fork functions the lower top hat hydraulic bump stop enters the bore of the valve body on fully compression and you don't want it to catch on the shim.

I guess even after having taken a fork fully apart, I still don't really understand the dynamics of the whole, and the functions of the parts).

It took me some time to fully understand it. If you are going to solve this you have to get your head around exactly how the forks function. Do you have Microsoft Word ? I can send you a lot of information I've collected.

Also, is the function of the shim to ensure that there is no space between the valve housing and the perforated washer, as well as between the valve housing and the circlip?  

The shims fits at the lower end between the valve body and circlip so yes it pushes the valve body hard up against the valve plate. I guess there is no reason you couldn't fit the shim at the top between the valve body and valve plate except it would increase the travel of the valve washer slightly. The distance the washer moves is a dead zone between compression and rebound damping so it wouldn't be ideal. It would be easier on the shim though.

[quixotic]

Do you have Microsoft Word ? I can send you a lot of information I've collected.

That would be great.  Thanks.  You can send it to ebedford at rdcounty dot ca

[quixotic]

Thanks for all the info, Barry.  Very much appreciated.

I assume my symptoms would direct me more towards the shim fix than the nylon washer fix.  

For the shims, would I press down on the perforated washer while everything is still on the damper rod, and then see if there's any space above/below the valve housing?  Then fill that space with a shim and insert it between the valve housing and the circlip?

[Barry]

For the shims, would I press down on the perforated washer while everything is still on the damper rod, and then see if there's any space above/below the valve housing?Then fill that space with a shim and insert it between the valve housing and the circlip?  

The damper rod need not be inserted when shimming the valve body. Just insert the perforated valve plate and valve body together into the stanchion recess and fit the circlip. You can then check if there is any vertical play and measure it with a feeler gauge.