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Old 02-02-2013, 12:55 PM   #1
CanadaBiker OP
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R100/7 fork advice

I felt that my forks needed some attention: sagged, reduced travel, slow rebound. ( although I have no context with these bikes--maybe the front forks kinda suck from new?) I was going to have a BMW dealer rebuild them for me, but after reading a bunch of threads here, some advocated just changing oil and maybe springs--if the seals didn't leak, which mine don't.

First a few measurements (not sure if they are helpful?):

Bike on centre stand, front wheel off the ground: centre of axel to top of chrome fork cap: 31 1/2"
Bike on ground: centre of axel to top of chrome fork cap: 29 1/2

So 2 inches of sag? If I did this correctly?

Bike on ground: from ground to centre of key switch: 36" (just in case someone else might measure their bike this way and let me know their results?)

Leaving forks on the bike:

I drained the oil, and it's pretty decent; no chunks, or sludge, mostly blue in colour, with a few swirls of grey.

I pulled the springs from the top, and laying on the ground they measure 570mm in length, and have yellow paint on the top of the spring.

Also, my parts don't look like any diagram I could find. All I have is the chrome cap, with plastic/fibre washer, and then the 35mm fork top cap bolt. No spacer on the bottom nipple of the cap bolt, nor any oil fill plug (fillister-head screw) that screws into the cap bolt.

So:

Even if the springs are the correct length unsprung, maybe they have weakened over time, and are saggy / lost their rebound? Does the yellow paint indicate factory original? ( I thought I read at MAXBMW, that BMW replacements springs have white paint on the top?)

If I replace, I was thinking of just going with the BMW ones, but the "COMPRESSION SPRING REINFORCED" #31 42 1 232 017 versions as recommended by MAX. (I'm not a big guy, rarely ride two-up, or super packed with gear and luggage)

Are my parts in order? My bike just doesn't have the small oil fill plug on the inside of the fork top cap bolt? (actually I just checked and I don't even have a small thread on the inside of the cap bolt, just the larger female thread for the chrome trim cap.)

If my seals are not leaking, think I should just change the oil and maybe the springs, and see how she goes?

Thanks for any advice!

OK BIG EDIT:

I think I might be an idiot.

I loosened the lower triple clamp on the left side, in the hopes of sliding out the headlight bucket ear. They need painting. And I realize I can pull out the upper fork tube, exposing the seal, etc. I'm I ok, as long as I only do one side at a time?

Should I pull the circlip and pull the rod from the upper for any service or check?

Obviously I should do the seals now, eh? Can I just pry them out and press in the new ones?
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Old 02-02-2013, 02:01 PM   #2
Stan_R80/7
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A few weeks ago I changed the fork oil on my '78. Mercon V ATF fluid was used with a volume of 265 ml. That amount comes from my 1979 Clymers manual, not the latest printed volumes. The previous change was using PJ1 7.5 wt oil but with 235 ml per fork.

The quart of ATF cost ~$4 and was easy to find. The Mercon V specs are about that of 7.5 wt but with more detergent and seal conditioners. Something to consider. Good luck!
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Old 02-02-2013, 03:21 PM   #3
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Canada-

Your fork caps set up is correct,afaik.

To be honest, I've never removed the fork tubes for maintenance or rebuild; I do it from the bottom... your's came out easily?

But, you may as well change your seals as long as you're "in there".

Do you have a Clymer,etc?
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Old 02-02-2013, 04:28 PM   #4
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I am about to tear down the front end including the forks on my R100/7, (I have done this lots of times). I will try to take some measurements.

The standard forks aren't bad for the 1970's. I use progressive springs. Lots of people don't seem to like them but I do. I replaced the original springs as I found was scraping the heads on bumpy corners, the progressives fixed that.

You don't have to change your fork seals every time but if it hasn't been apart before (that you know of) then change them and save yourself the grief of having to tear it all down again.

Yes, pull everything apart while its down so you can inspect it and clean it.

cheers

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Old 02-02-2013, 04:49 PM   #5
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Two inches of sag with no one on the bike? You want less than that with you on the bike. Around 1.5. Set up your rear sag with you on the bike to be between about 1.5 and 1.25 inches and then adjust preload spacers on the STOCK springs to ruffly match up your sag in the front. Whatever feels best to you. Some of those seventies bikes had two inch preload spacers from the factory. Whatever it takes. 5 or 7.5wt Spectro fork oil and make sure they are lined up. That's as good as they get without re-valving them.
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Old 02-02-2013, 05:04 PM   #6
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Quote:
Originally Posted by supershaft View Post
Two inches of sag with no one on the bike? You want less than that with you on the bike. Around 1.5. Set up your rear sag with you on the bike to be between about 1.5 and 1.25 inches and then adjust preload spacers on the STOCK springs to ruffly match up your sag in the front. Whatever feels best to you. Some of those seventies bikes had two inch preload spacers from the factory. Whatever it takes. 5 or 7.5wt Spectro fork oil and make sure they are lined up. That's as good as they get without re-valving them.
Do I adjust preload by trying different size spacers at the bottom or top of the springs? I've heard people just cut various pieces PVC pipe?

Oh, and do I measure sag as the difference between the bike being on the centre stand and then off the stand and me sitting on it OR off the centre stand no one on it, and then me on it? (If that makes sense)
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Old 02-02-2013, 06:14 PM   #7
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You can use PCV pipe on top of the springs. Once you are in your ballpark, I adjust prelaod with washers. You might not be able to measure any difference in sag but you sure will be able to feel the difference in the ride. Sag is the difference between fully extended and you setting on the bike with no help from any stands. I just sit on the bike and slightly lean on something while I make the sag measurements.
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Old 02-02-2013, 06:14 PM   #8
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Another 100/7

I began my fork rebuild on my 100/7 today as well. I had the same concerns about the lack of pieces at the top. I had only the chrome plated top cap and the fiber washers were missing. I just purchased this bike from the original owner a couple of months ago. The bike has only 10,000 miles on it. The motivation for the service was due to heavy duty stiction. So I purchased the Progressive springs and tore things down to see what needed to be addressed. The Progressive springs ship with PVC spacers to make up the length as they are shorter than the stock springs. The boots were cracked and even though the seals weren't leaking, I will certainly change those. I ordered the "rings" for the dampener rod and the sealing washers. The biggest puzzle was the 3/4" of waxy goo that filled the lower cap. I have no idea what that was or what caused it. Looking at the microfiche it looks like it may be the remnants of the "ring" (31421231314). It appears that the fluid was relatively fresh and not gray. The parts are a few days out so the re-installation will have to wait. I have read many reports of the critical importance of getting the tube alignment perfect when putting things back together. I plan to test the dampener and slider for smooth action before adding the springs and buttoning the forks back up. Crossing my fingers!

Post your progress and success to give the rest of us some inspiration!
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Old 02-02-2013, 06:30 PM   #9
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Originally Posted by supershaft View Post
You can use PCV pipe on top of the springs. Once you are in your ballpark, I adjust prelaod with washers. You might not be able to measure any difference in sag but you sure will be able to feel the difference in the ride. Sag is the difference between fully extended and you setting on the bike with no help from any stands. I just sit on the bike and slightly lean on something while I make the sag measurements.
Ok thanks. I guess I'll have to really work at the the preload. Seems tricky.

Quote:
Originally Posted by Norcal_Rider View Post
... The bike has only 10,000 miles on it. The motivation for the service was due to heavy duty stiction. ..... The Progressive springs ship with PVC spacers to make up the length as they are shorter than the stock springs. ..... I ordered the "rings" for the dampener rod and the sealing washers. The biggest puzzle was the 3/4" of waxy goo that filled the lower cap. I have no idea what that was or what caused it. Looking at the microfiche it looks like it may be the remnants of the "ring" (31421231314). .... I have read many reports of the critical importance of getting the tube alignment perfect when putting things back together. I plan to test the dampener and slider for smooth action before adding the springs and buttoning the forks back up. Crossing my fingers!

Post your progress and success to give the rest of us some inspiration!
Wow, 10k miles, that's amazing!

Where did you order your springs from? And the spacers are specific to the R100/7? Can I ask why you choose the Progressive and not the OEM "reinforced"? #31 42 1 232 017

When you say the 'rings', do you mean those tiny little ring clip thingys that are stacked 3 at a time in that groove?

I haven't removed the bottom screw plug yet, I didn't realize that the ring spacer could disintegrate. I'll have to pull mine out before I place an order.

Ugg, I hadn't heard of the tube alignment either. (I'm such a noob) Doesn't the upper just go into the lower, and etc? Then tighten the top nut, bounce the forks, tighten the lower triple clamps? Is there more to it?

I'll post pics as I go. Hopefully I don't frack it up!

Good luck with yours!
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Old 02-02-2013, 06:46 PM   #10
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Quote:
Originally Posted by CanadaBiker View Post
Ok thanks. I guess I'll have to really work at the the preload. Seems tricky.



Wow, 10k miles, that's amazing!

Where did you order your springs from? And the spacers are specific to the R100/7? Can I ask why you choose the Progressive and not the OEM "reinforced"? #31 42 1 232 017

The Progressive springs were purchased from one of the online motorcycle warehouses. They are specific to our year and model (but probably fit others). I have used this brand of spring in the past with good results. The spacers as shipped should be a good start for preload. I didn't consider the OEM because of my good history with Progressive springs.

When you say the 'rings', do you mean those tiny little ring clip thingys that are stacked 3 at a time in that groove?

Yes those are the ones. They act just like piston rings in your engine, creating a seal and therefore pressure in compression and rebound.

I haven't removed the bottom screw plug yet, I didn't realize that the ring spacer could disintegrate. I'll have to pull mine out before I place an order.

One of the bottom screws was a little more stuck than the other and I damaged the internal hex on the end, so I had to order a new one.

Ugg, I hadn't heard of the tube alignment either. (I'm such a noob) Doesn't the upper just go into the lower, and etc? Then tighten the top nut, bounce the forks, tighten the lower triple clamps? Is there more to it?

On "other" bikes that is the way it works, but Airheads...that's a different story from what I can gather. There are many stories and tutorials about proper tube alignment. I suppose you could get lucky. My experience is usually not centered around good luck.

I'll post pics as I go. Hopefully I don't frack it up!

Good luck with yours!
Thanks!
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Old 02-02-2013, 07:18 PM   #11
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Despite the internet buzz, all you need is regular stock springs. Setting preload is time consuming, not tricky. That's why most never do it and why most airhead forks are setup like a slow motion train wreck.
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Old 02-02-2013, 07:32 PM   #12
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Quote:
Originally Posted by supershaft View Post
Despite the internet buzz, all you need is regular stock springs. Setting preload is time consuming, not tricky. That's why most never do it and why most airhead forks are setup like a slow motion train wreck.
I'm the kind of guy that will take the time, my only issue will be that I'm not entirely sure what to look for / feel.

I see that all the usuals suspects of OEM parts sellers list two different BMW springs sets.

Compression Spring - #31 42 1 231 358 & Compression Spring Reinforced - #31 42 1 232 017

MaxBMW suggests only using the first set if you are very light, etc.

When you say 'regular stock springs" do you recommend the first one vs the 'Reinforced?

Thanks!recommend
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Old 02-03-2013, 01:33 AM   #13
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I went to hell and back trying to sort out an ATE front end, spent a small fortune on new parts and springs, made spacers trying to get the preload set right. The biggest mistake I made was not fitting new wiper rings in the dampers and using Motobins Aeroshell fork oil. I've never taken a front end apart so many times before.

After all the fannying about I replaced the damper rings and used a decent fork oil. Turns out there was nothing wrong with my springs and I didn't need any preload. The ATE forks give a nice action when they're sorted, just like the brakes. I actually prefer them to the later Brembo front ends but the big advantage with the later set up is there's no messing about it's all quick and easy.

Those damper rings are crucial to the forks working correctly. Check the ball bearings in the damper rods are free to move and that they seal correctly.

The aeroshell oil I used was causing the forks to stick and generally giving a very poor action. Swapping to Belray cured all the sticking issues.

Heres my post from a couple of years ago where the guys helped me out http://advrider.com/forums/showthrea...ighlight=forks what I should have done was get everything in there as near to perfect using the standard parts instead of masking the real issue with preload spacers.

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Old 02-03-2013, 03:47 AM   #14
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Quote:
Originally Posted by Norcal_Rider View Post
The biggest puzzle was the 3/4" of waxy goo that filled the lower cap. I have no idea what that was or what caused it. Looking at the microfiche it looks like it may be the remnants of the "ring" (31421231314). It appears that the fluid was relatively fresh and not gray. The parts are a few days out so the re-installation will have to wait. I have read many reports of the critical importance of getting the tube alignment perfect when putting things back together. I plan to test the dampener and slider for smooth action before adding the springs and buttoning the forks back up. Crossing my fingers!

Post your progress and success to give the rest of us some inspiration!
Just did the forks on my 74 R90/6 with 19k miles on it and Exactly same scenario. I'd like to know what it is. The fork seals looked intact (but hard as a rock). Definately an improvement yesterday when checking for stiction w/o springs in.

Hope yours goes well!
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Old 02-03-2013, 06:18 AM   #15
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Quote:
Originally Posted by Rob Farmer View Post
I went to hell and back trying to sort out an ATE front end, spent a small fortune on new parts and springs, made spacers trying to get the preload set right. The biggest mistake I made was not fitting new wiper rings in the dampers and using Motobins Aeroshell fork oil. I've never taken a front end apart so many times before.

After all the fannying about I replaced the damper rings and used a decent fork oil. Turns out there was nothing wrong with my springs and I didn't need any preload. The ATE forks give a nice action when they're sorted, just like the brakes. I actually prefer them to the later Brembo front ends but the big advantage with the later set up is there's no messing about it's all quick and easy.

Those damper rings are crucial to the forks working correctly. Check the ball bearings in the damper rods are free to move and that they seal correctly.

The aeroshell oil I used was causing the forks to stick and generally giving a very poor action. Swapping to Belray cured all the sticking issues.

Heres my post from a couple of years ago where the guys helped me out http://advrider.com/forums/showthrea...ighlight=forks what I should have done was get everything in there as near to perfect using the standard parts instead of masking the real issue with preload spacers.
Thanks Rob,

When you say the wiper rings / damper rings, do you mean those tiny thin rings, (almost like piston rings) stacked 3 at a time in the groove? The fiche just calls them "Rings" # 31 42 2333753

Did you go back to BMW original springs? Do you know if you used the standard BMW Compression Spring - #31 42 1 231 358 or BMW Compression Spring Reinforced - #31 42 1 232 017

Also, did you use the 5wt Belray?
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