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Thread: 90 R 100 GSPD suspension upgrade

  1. #46
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    Quote Originally Posted by AntonLargiader View Post
    I'm going to be going through a few sets of R100GS forks in the next few months so this subject is back on my radar, too. I recently bought an R100GS with very stiff front suspension; I know there are some mods in there but I don't know what. The P.O. liked very stiff suspension so there may be a GV in there with a stiff spring or heavy preload. OTOH a customer has an R100GS and a recent ride showed that it had a very soft suspension (we switched bikes and it was eye-opening for both of us) so I need to come up with a middle ground for both of us based on what I find inside my own forks.
    looks like we are in the same boat... i look forward to hearing your thought on the matter.

    I did a WP4860 front end on the G/S which is AWESOME, but I would like to see if there is an adequate mod for the stock GS forks before I start contemplating major refit of the GS.
    '81 R80G/S(wp4860 forks, Henderson triple clamp)
    '10 Husaberg FE450, '10KTM 250XC-W
    Past BMWs: '68 R50/2, '77 R80/7, '87 R80GSPD, '76 R60/6, '85 K100RS, '91 R100GS,'87 R100RS

  2. #47
    not lost til out of gas 128521's Avatar
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    hey Guys, yes this mod is working excellent. here are a couple of pictures from my trip on the WABDR this summer. we went from Carson WA to Lake Chelan WA on the BDR. that is sections 1 thru 4, we were stopped by a forest fire as section 5 north of Lake Chelan was closed. these pic's are from the washout in section 3, which we rode thru because the guy with the GPS ( that would be me ) missed the bypass. my friend went right up on a dr 650 , I rode the first part then got off and worked the controls with my friend holding the back, and we walked/powered it up. I did ride thru the next 2 dips ( you can find pic's on ADV if interested ) fully loaded! I will guarantee you it was more challenging than the picture looks. we rode thru rocks, ruts, sand, steep twisty narrow jeep roads, that at times were above my skill level. still I only dropped the bike twice in 4 days. both times because I was going too slow.
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    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  3. #48
    not lost til out of gas 128521's Avatar
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    here are a couple more shots of the BDR south of Lake Chelan WA. the smoke is the fire that stopped us.
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    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  4. #49
    Dress for fall & avoid it AlanColes's Avatar
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    Glad to know you're still happy with the setup.

    I've been trolling this thread and since around the time you started it, but like Anton, just bought a GS this year (1991 R100GS Bumble Bee) and it should have the front-end rebuilt. Much too soft and worn for my 195 lbs without gear. ;-)

    Nice to see the shots of your BDR trip, I'll definitely checkout the ADV pics as it will surely bring back memories of the 3 months I spent in the summer of '76 climbing in the Leavenworth and Wenatchee areas, very fond memories.
    Regards, Alan - President BMWONS - MOA Charter Club #097, BMWMOA/BMWRA/BMWONS/Airheads
    Current: '14 R1200RT / '06 Ducati ST3s / '91 R100GS / '86 R80RT / '75 R90S / '73 850 & '70 750 Commando Prev: '04 R1150RT / '81 Honda GL1100 / '77 Suzuki GS750 / '73 Norton 850 Commando

  5. #50
    I just got my spare forks back together (stock except for the springs) and I will try to swap them into my PD tomorrow or early next week. Then I can crack my PD forks open and see what's going on in there. Should have something by mid-week.
    Anton Largiader 72724
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    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  6. #51
    I've made a bit of progress. But first: Jim, do you have a record of exactly what springs RaceTech sent you?

    What I didn't like about my PD forks was the stiffness. It was so stiff I couldn't even figure out if the damping was any good. I found that the springs inside were .84 stiffness (stock is about .50) but moreover they only had 175mm of stroke before coil bind. With a tiny bit (10mm) of preload that's 165mm fork travel on a bike that normally has 210mm, and the coil bind becomes the bottoming stop.

    Based on your experiences with them, and pretty much everything else I have read, it's pretty clear that RaceTech didn't really bring any expertise into this process. They took a big guess and then corrected themselves as they went, since people like you were calling because the existing instructions at the time made no sense. I'm not anti-RaceTech, I just realize that they're not experts on these forks. The owners, like you and me, are. These are not typical damper rod forks. All they really did for you was say "Yes" every time you learned something new.

    So, your springs look a lot like the S3234085 springs that I found in my forks, which they also specify for the K75. Some people like stiff forks and don't like a lot of travel, but I'm not in that group. They are 340mm long, with 31 coils, which perfectly matches the pic you posted. They make several stiffnesses; mine had 4.8mm wire. Do you have a model number?
    Anton Largiader 72724
    Tech articles
    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  7. #52
    FWIW it seems that Race Tech is not listing that short 3234 spring any more for the GS. They now list the 3452, which as its name implies fits into a 34mm fork tube and is about 520mm long. However, although their recommendations are for .7 ~ .9 spring rate depending on rider weight, the 3452 is only available in a few rates from .44 to .50. So maybe when customers ask for a spring matching their recommendation that they sell the 3234 instead? That's why I'm curious what spring ended up in Jim's bike and how.

    This week - hopefully today - I'll ride my PD with stock damping and aftermarket springs and then switch to the forks with the GV and stock springs. The spring rates on the two are practically the same so I don't expect much confusion from that. I'll find some square-edged bumps to ride over.
    Anton Largiader 72724
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    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  8. #53
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    Update...

    Quote Originally Posted by AntonLargiader View Post
    FWIW it seems that Race Tech is not listing that short 3234 spring any more for the GS. They now list the 3452, which as its name implies fits into a 34mm fork tube and is about 520mm long. However, although their recommendations are for .7 ~ .9 spring rate depending on rider weight, the 3452 is only available in a few rates from .44 to .50. So maybe when customers ask for a spring matching their recommendation that they sell the 3234 instead? That's why I'm curious what spring ended up in Jim's bike and how.

    This week - hopefully today - I'll ride my PD with stock damping and aftermarket springs and then switch to the forks with the GV and stock springs. The spring rates on the two are practically the same so I don't expect much confusion from that. I'll find some square-edged bumps to ride over.
    Anton, any update on your last ride with the GS forks?
    -------------------------------------------------------------------------------------------------------------------------------------------------------------
    2013 Triumph Tiger 800 (For Sale), 1992 BMW R100GS, 2004 Moto Guzzi Breva 750, 2014 Royal Enfield GT, 1990 Kawasaki Tengai

  9. #54
    I rode the bike a little bit but nothing big. Softer for sure, damping seems adequate and I did detect a little bit of wheel bounce over bumps. However, I think at least some of that was from the back wheel. There is an Ohlins back there and I had backed the damping off all the way to try to make the bike more comfortable. With a reasonable setup on the front now, it might be exposing the rear for being a bit on the soft side now. However, I just haven't had much time to mess with it. The 5W fork oil still isn't here and I don't have time to mess with it, so the emulator is still sitting in the spare forks leaning against the file cabinet.

    However, I am trying to catalog the various springs that I and others have encountered for these bikes. I've updated my web page to show them, although I don't have all of the details for all springs.: http://largiader.com/tech/gsforks/
    Anton Largiader 72724
    Tech articles
    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  10. #55
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    Thank you I will have a look!
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    2013 Triumph Tiger 800 (For Sale), 1992 BMW R100GS, 2004 Moto Guzzi Breva 750, 2014 Royal Enfield GT, 1990 Kawasaki Tengai

  11. #56
    Just saying this hasn't fallen off my radar. I have put the 5W oil in the left leg with the OEM spring so the fork legs are ready (as long as the preload winds up right). I have to say, that 5W oil makes for really minimal damping in that leg! Which is the idea. In the process I confirmed that the 410cc refill volume is correct, which was questioned in a different thread. The manual calls for 470 cc after rebuild, and 410cc when just changing the oil. The left fork leg does indeed retain 60cc of oil if you don't disassemble or invert it, mostly because oil fills the damper rod and can't escape.

    The right leg with the emulator has 10W. The difference (compared to a leg without the emulator) is noticeable just moving the fork by hand. More compression damping.

    At this point I'm just looking for a nice enough day when I have enough time to find a nice rough surface to test ride on. Then I'll ride that with both sets of fork legs.
    Anton Largiader 72724
    Tech articles
    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  12. #57
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    I thinking of going this way for my '89 GS but then I found a half decent set of DRZ from a E model - open cartridge type like the wp4860's on my R80G/S. These will provide adjust of rebound and compression adjustments from outside the fork.

    These are getting shortened with 75mm spacers and new springs. The valving has already been done by a excellent suspension shop in the area.

    I purchased a set of triples from the Netherlands that mate the DRZ forks the GS geometry and fork headlight bucket.

    The BMW sport suspension upgrade - WP rear shock - is being checked over and renewed by my local suspension shop over this winter as well.

    I have all winter to get the GS back together, I won't know how this setup performs until the spring.

    I will post a few pics of the Triple mounted.
    '81 R80G/S(wp4860 forks, Henderson triple clamp)
    '10 Husaberg FE450, '10KTM 250XC-W
    Past BMWs: '68 R50/2, '77 R80/7, '87 R80GSPD, '76 R60/6, '85 K100RS, '91 R100GS,'87 R100RS

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