F800GS Fork Clacking Noise

Discussion in 'Parallel Universe' started by davidpetersen, Apr 22, 2009.

  1. davidpetersen

    davidpetersen BestRest Adventurer

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    There's been lotsa speculation on the causes of F800GS front end clacking. I think I may have found one cause, and I came up with a solution.

    I was installing new Ohlins front springs so I had the upper tube caps off, and the old springs removed. I noticed that there's a black plastic inner spring guide, on the upper damper rod, at the top of the tube. It's got 4 ribs on it, and it's about 8" long. Refer to part #3 in the diagram below (these drawings are SIMILAR to the actual parts in my forks, but not identical).

    Photo being updated 3-29-10

    The spring guide has some free-play on the damper rod. It can move up and down a bit as it guides the spring and keeps it concentric on the rod. The lower position is limited by internal stops, but the upper position is determined by a 13mm jamb-nut that keeps the upper cap affixed to the end of the damper unit. The upper cap is threaded down onto the end of the damper unit, and the jamb-nut keeps the cap from coming loose off the end of the damper unit.

    It's difficult to loosen that jamb-nut because you have to grip the damper unit at a point below the spring guide so it doesn't turn when you torque the nut. You'll need a long pair of needle nose pliers that can fit between the coils of spring. Or, you can turn the jamb-nut one way as you turn the upper cap the other way, and they'll break free of each other.

    My curiosity was stirred by the free-play of the black spring guide, so I reassembled the guide, the jamb-nut, and the upper cap, without the spring itself, so I could see how things fit. I worked the spring guide back and forth on the damper rod, and lo-and-behold I heard a familiar sound! The spring guide made a clacking noise at the top of it's travel, when it hit the jamb-nut. Maybe I was onto something here.

    Here's what the spring guide, damper rod, jamb-nut, and upper tube cap look like, when the spring guide is in the lower position:
    [​IMG]

    And here it is with the spring guide in the highest position:
    [​IMG]

    When the free-play is measured, it's about 1/4":
    [​IMG]

    I have a bunch of prototyping bushings and spacers around the shop, so I picked our a couple 1/4" x 1" diameter thick buna rubber bushings with a 5/16" center hole, just the right size to fit on the upper threaded end of the damper rod. The bushings were smaller in diameter than the 4 fins of the spring guide, so they won't hit the spring.

    I threaded the jamb-nut on the end of the damper rod, and slightly compressed the bushings, then threaded the caps in place. I then tightened the jamb nuts up against the bottom side of the caps and checked for clearance between the bushings and the jamb-nuts. Perfect.

    I took it all apart, installed the springs into the tubes, fit the rubber bushings and jamb nuts, and top cap in place, and tightened them against each other. No more free-play of the spring guide, it was snug and comfy.

    Here's what it looked like:
    [​IMG]

    The rubber bushing can be seen below the jamb-nut and the spring. There's a bit of grease on the bushing, which I found necessary to get my wrench onto the jamb-nut. The rubber bushing cuts down on your available working space, so my usual 13mm wrenches wouldn't fit. I used a grinder to thin out the end of an old 13mm wrench, until it was about 3/32" thick and could slip into the gap between the bushing and the plastic cap, and onto the 13mm nut. I replaced the fork caps and tightened the pinch bolts.

    Now for the test ride. :ear Before the new Ohlins springs and my rubber bushing mods, the front end would clack like a barnyard goose everytime I hit a sharp bump. But now the clacking sound is gone. Silencio. Shhhhh.

    A hush falls over the crowd... could this be the solution we've been seeking? Well, it worked for me. YMMV.

    Update: I had so many requests for these bushings, that I put them on the website. Click here: KlackStoppers

    PS. The new Ohlins front springs work great, as does the new rear shock. Money well spent. I got them from Stig Pettersson at PPS.
    http://www.bestrestproducts.com/t-links.aspx

    Update: The Griz has taken the noise investigation to the next level! Scroll down and read his postings, they shed more light on the possible causes (and fixes).

    We're getting there!




    .
    #1
  2. Bayner

    Bayner Long timer

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    Excellent diagnosis and repair Dave!!
    #2
  3. The Griz

    The Griz Long timer

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    So can this fix be accomplished without removing the forks completely? Can I just remove the fork tube caps and get at these parts? Also, where can I pick up a couple of those bushings? Thanks a ton!
    #3
  4. davidpetersen

    davidpetersen BestRest Adventurer

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    You don't need to remove the forks completely. Here's the drill:

    1. Bike on centerstand

    2. Fit a floor jack under the bash plate, the jack will be used to carry the weight of the front of the bike when the caps are removed. Crank up the jack until the front end is slightly off the ground

    3. Loosen handlebar clamps and remove bars

    4. I had an overhead rack and ran a couple bungees from the bars to the rack so the bars were kept up and out of the working area

    5. Loosen the upper pinch bolts on the fork tubes

    6. Unscrew upper fork caps

    7. Gently and SLOWLY :eek1 release the floor jack; as you lower the jack the front end will go down and the ends of the springs and caps will move out of the forks.

    8. Continue lowering the jack until the forks are "bottomed out"

    9. The ends of the springs, the caps, the threaded damper rod, and the jamb-nut will be exposed.

    10. With a 13mm wrench, slip it between the coils of the springs, and try to loosen the nut while you keep the top cap from turning.

    11. #10 didn't work for me, so I used a pair of needlenose pliers and slipped them between the springs at the lower end of the black plastic spring guide. I held the rod from turning, while I loosened the jamb-nut.

    12. Once the jamb-nut is loose, the end cap spins off the threads at the end of the damper rod.

    13. Remove the plastic spring spacer, pull out the spring. Do it slowly and twist it counterclockwise so the oil runs off the coils into the fork body, instead of all over the bike.

    14. Black plastic spring guide will be exposed and free to examine.

    Note - The damper rod will want to slowly retract down into the fork tube. If this happens it's a real pain to retrieve, so keep an eye on it, or better yet tie a piece of string or ziptie on it so you have a tail you can grab and pull it back up.

    15. Without the spring, fit the spring guide on the damper rod, fit the the jamb-nut on the threads, and spin the top cap on the threads until it bottoms out.

    16. Finger tighten the jamb-nut against the bottom of the top cap.

    17. Observe the up-and-down free play of the spring guide, between the lowest position, and the upper position where it touches the jamb-nut. Listen to the sound it makes when you really whack it upward. :ear

    18. Measure the amount of free play between the jamb-nut and the spring guide.

    19. Select an appropriate rubber bushing to match the free-play. My bushing was 1/4" thick, 1" diameter, with a 5/16" hole. ** see bottom of page.

    20. Take everything apart again, and fit the spring into the tube, along with the spring guide.

    21. Slip the rubber bushing onto the end of the damper rod.

    22. Fit the jamb-nut and finger tighten it down onto the bushing; you will be compressing the bushing a bit.

    23. Fit the top cap to the end of the damper rod, and spin the cap down until it bottoms out. It should not be touching the jamb-nut.

    24. Tighten the jamb-nut firmly against the top cap.

    25. You may need to modify a 13mm open end wrench, by grinding the sides until it's less than 1/8" thich. Otherwise it's impossible to fit the wrench between the rubber bushing and the top cap.

    26. The rubber bushing should be in a very slight compression between the jamb-nut and the spring guide.

    27. Elevate the floor jack; as you do the fork springs will retract into the tubes.

    28. Lubricate the top cap's rubber o-ring seals with a bit of grease.

    29. Press the caps down until they engage the inner threads of the tubes, and tighten the caps to recommended torque settings

    30. Tighten the pinch bolts of the triple clamp.

    31. Elapsed time: less than an hour.

    32. For safety reasons, always remove the floor jack before riding the motorcycle. :lol3



    ** The rubber bushings I used were from a prototyping project, and needed to be modified to fit by cutting off a shoulder. I'll offer these for $7.00 PPD thru my website. They're called the KlackStopper. Click the link to go to the ordering page.

    Please don't bust my chops for "selling them" here, instead of the vendor forum. They're being offered as a service to my fellow F8GS riders, not as a moneymaking venture.

    Or you could make your own. But whatever you decide, use rubber, not something hard like stacked washers.

    .
    #4
  5. itsatdm

    itsatdm Long timer

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    It is easier to take the forks off, imo. My home made "hold the spring down thingy". Depress the spring and slip under the lock nut..

    [​IMG]
    #5
  6. marc morgan

    marc morgan Been here awhile

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    Dave:

    Way to go. I think that is exactly what it is. I've had that since day one. I guess now , I see that it is not really a problem so if I can live with the rattle, at least I'm not doing any harm to the bike. Thanks.
    #6
  7. davidpetersen

    davidpetersen BestRest Adventurer

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    Taking the forks off the bike is easier than removing the top caps? :huh

    The spring thingy is a good idea, but it's gotta fit in the same space as the new rubber bushing. That empty space is what allows the black plastic spring guide to move up and down and clack. So the spring thingy may not fit once you've inserted the new rubber bushings.
    #7
  8. The Griz

    The Griz Long timer

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    Dave,

    I'd love to buy 4 of those rubber bushings from you. 2 extra in case I screw something up or they wear out!:D Let me know if this is possible. Thanks again for this write-up. I was convinced the clack was from the rotors and calipers. But your diagnosis makes a lot more sense.
    #8
  9. sillymike

    sillymike Yep! That's me...

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    Tag for interest!

    The GF just brought her new F800GS for servicing and she was complaining about that 'clacking' noise...

    Mike.
    #9
  10. svowles

    svowles Simon

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    I think I'll try this at the weekend.

    Being really lazy I might even try and split a rubber spacer with a sharp blade, push it onto the shaft and use a little blob of super glue to rejoin as once in place its looks like it can't go anywhere and it'll save wrecking a 13mm spanner.
    #10
  11. GB

    GB . Administrator

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    Thanks Dave, a great thread to be added to the Index thread.

    So this cure is purely for the sake of eliminating this noise and there's no other "issue" with the forks? :ear
    #11
  12. The Griz

    The Griz Long timer

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    That's a good idea! Only, how are you going to hold the spring back while you slip the split rubber spacer on?

    I'd just go to the hardware store and buy a cheap 13mm open end and sacrifice it. For me it's a small price to pay for silence riding over the bumpies. Especially when I'm riding this beast off-road!:ricky That's when the noise rears its ugly head the worst for me.
    #12
  13. The Griz

    The Griz Long timer

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    Yeah, the forks will operate completely normal without this cure. It's just that they'll operate noisily. This is just all about killing the annoying "clack, clack, clack" when driving down the road.
    #13
  14. The Griz

    The Griz Long timer

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    #14
  15. DolphinJohn

    DolphinJohn Caveman

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    As I reached the apex of my very first flight on my F800,
    I had time to think to myself "oh dear, I've really launched her,
    I hope I don't bottom out upon landing" (maybe not the exact words)
    To my pleasant surprise, she landed nice and level, and very cushy.

    It was kind of an accidental flight but kind of not. I found a hidden dirt
    road on my way back from camping, with a long line of oversized whoops,
    spaced about 20 yards apart. I think it's ridden a lot by four-wheelers.
    They were actually dried out pools with a nice big berm in front.
    I hit the first few conservatively then they got a little steeper and I got a little braver until finally snapping the throttle in second gear like I was on a CR250.

    I swear I was 10 feet in the air if I was an inch.



    ok, maybe not. probably 4 or 5 though, and it really handled it well,
    with my 185 lbs. + gear and about 20 lbs. of camping gear on the back.

    I don't remember hearing a clack. :dunno

    Also, after careful inspection, my drawers remained unsoiled. :clap
    #15
  16. bxr140

    bxr140 Flame Bait

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    :huh

    :1drink
    #16
  17. The Griz

    The Griz Long timer

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    After performing the fix described in this thread, I can now report my findings. These findings conclude (after much testing and isolation of culprits) that there are other things involved in addition to the spring guides that create noise on the front end of this bike. These noisemakers include: the floating brake rotors, the floating calipers, loose steering head bearings, and of course the spring guides within the shocks themselves hitting the fork tube cap lock nut. I have found that the sole culprit may not the spring guides alone. I have also found that on some people's bikes that they are the sole culprit. Each bike is different. Which of the culprits are the actual noisemakers differs from bike to bike. As an example: I have finally silenced my front end. For me, in the beginning, there were three things I thought were making noise on the front end of my bike:

    1) Loose steering head bearings

    2) Movement of internal spring guides

    3) Very loose floating rotors

    With each of these things being addressed, my bike became more and more quiet (with the exception of #2). Like I said, initially my bike was way loud with noises in the front when I drove it home from the dealer. I tightened the steering head bearings. It got quieter and tighter. Next, I installed some rubber bushings as described in this thread. I didn't really hear a change. Still "clack clack clack". And now, I zip-tied the floating rotors to prevent play within them. Low and behold.... Silence. On my bike, the floating rotors were the noisiest part. When I opened up the forks and tried to move the spring guides on the damper rods, they didn't move. It's like they were stuck in the down position. It took quite a bit of force to break them loose from the down position to see and hear the movement as described in this thread. This is probably why they weren't causing me noise issues in the first place.

    This is just my experience. Again, my theory is that each bike is different. And on each bike there are different causes. I'm keeping the rubber bushings in just for the hell of it, to rule out that culprit. But for me, it was the floating rotors that were the noisiest culprit. Next noisiest was the steering head bearings being loose. And it turns out that for me, the spring guides weren't making noise in the first place. But now that I've broke them loose, I'm sure they would without the rubber bushings! Also, I've ordered Lucas non-floating rotors from Wunderlich. In the meantime, I'll keep the zip-ties on the stock rotors!! Mmmmm....smooth silence.

    Pictures of zip-tied rotor:
    [​IMG]
    [​IMG]
    #17
  18. Lion BR

    Lion BR I'd rather be riding

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    You are some piece of work, man.


    #18
  19. The Griz

    The Griz Long timer

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    In no way, shape, or form am I trying to contradict the OP's findings in this matter. I'm just reporting my experiences with the matter, as was he. On some people's bikes the spring guides might be a clack-maker. I'm not denying that. I'm just stating that on mine they weren't.

    Very poor form on your part, Lion BR.
    #19
  20. WoodWorks

    WoodWorks House Ape

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    Oh, Lordy. :rolleyes

    David
    #20