F800gs - Almost perfect except for poor suspension.

Discussion in 'Parallel Universe' started by mac444, Oct 22, 2008.

  1. johngil

    johngil Reseda, CA

    Joined:
    Jun 28, 2007
    Oddometer:
    3,814
    I thought I had really broke my Bitubos beyond repair. It wasn't pretty.

    [​IMG]

    The guys at Catalyst Reaction didn't blink an eye and even made their own tooling to re-charge the cartridges.

    http://www.catalystsuspension.com/

    Ask for Tige or James.
  2. MTrider16

    MTrider16 Ridin' in MT

    Joined:
    Oct 16, 2006
    Oddometer:
    1,855
    Location:
    Eastern Montana
    Well Kids, It looks like I need to write a retraction. After pounding around the CDT following some moto's and then trying to find jeep tracks in the Custer National Forest and in the Bighorn Mountians with the Mobius gang, I have about 2500 miles on the Ohlins Nix kits with rear shock. They have done very well at keeping the pig in line over some rough trails, as well as pounding out some pavement connecting sections. I'll give them a thumbs up even with the $2100 price tag for the fronts and rear.

    David
  3. Singletrack_mind

    Singletrack_mind Cave Man

    Joined:
    Aug 29, 2008
    Oddometer:
    453
    Location:
    Northern New Mexico
    Here's a question that's un-related to this otherwise interesting fork discussion:

    I have a 2009 with 45K miles on it. I had Trail Tricks do the front and Race Tech re-valved and serviced the rear last spring. The Trail tricks fork mod was a very subtle improvement, the Race Tech shock re-valve & straight-rate spring was a bigger improvement, but neither end is perfect. now, in fact, something's gone actually wrong & I can't find the problem.

    Something related to the rear wheel gives a jarring clunk through the seat and frame over certain bumps. This has been going on for a month or so, perhaps getting more pronounced with time. It is hard to induce reliably, but the ride up my dirt road road or certain speed bumps makes it obvious. There is no sound that I have noticed associated with it. I have checked wheel bearings, swing arm bearings & shock mounts, found no play. I removed the seat and cover and inspected the upper mount which has been know to bend and break. No problem there. I adjusted the chain. In case I was wrong about it being in the rear, I checked headset bearings and fork bushings too. Center stand and side stand seem the same as always, and this thunk seems much too solid for a bouncing centerstand anyway. I took my Jessie bags completely off, and removed the tool kit from under the seat in case it was knocking around. Seat seems the same as ever, a little play in the back, but this is a hard thunk, like bottoming the suspension. I have checked that preload and rebound are still where I set them. There is oil visible where the inner and outer shock jackets slide over eachother, but no oil dribbling off the bottom of the shock, hence no real leak. Bouncing the front or rear of the bike at a stand-still does not produce the thunk. Rebound damping still seems to be functional. I talked to Race Tech and they said there isn’t really anything that could change inside the shock (although I know internals can and do break; witness Johngil's shim stack, above).

    So has anyone had an experience like this, and if so, what was it?
  4. Indy Unlimited

    Indy Unlimited Long timer

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    Jan 21, 2007
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    1,590
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    Hey Singletrack mind,

    I suspect your bearings are shot in the upper and/or lower mount of the shock. This crates a clunk since the bearing now has play and the shock may be fine.
  5. Singletrack_mind

    Singletrack_mind Cave Man

    Joined:
    Aug 29, 2008
    Oddometer:
    453
    Location:
    Northern New Mexico


    Indy, I'd like to believe you and suspected something like this initially, but I'm pretty sure that'd show up as vertical play. With the bike on the center stand and the wheel in the air I'd expect to be able to feel that when tugging upward on the wheel or swingarm, but I can't, there's no apparent slop there.

    At some point I'll pull the shock to have my local shop strip & inspect the internals, that'll be the moment to give the upper and lower eyes a real close look.
  6. Indy Unlimited

    Indy Unlimited Long timer

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    Okay but very strange to see that it is in the internal shock. Let us know the final verdict.
  7. mxz

    mxz Adventurer

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    Sep 11, 2015
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    78
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    Riga, Latvia
    The simplest solution is usually the right one. Uhh, have you tried wiggling the brake rotor (or disc as we call them in Europe) with your hand to see if it has play? Back and forth and side to side? F800s have full floating rotors that tend to change over time in terms of loseness and start to introduce play. The pins that hold the rotor can become a bit loose and upon impact the rotor hits the mount and clunks. Some brand new (like mine) have a metallic clunk both front and rear straight outta factory! It's a bit annoying really.
  8. Singletrack_mind

    Singletrack_mind Cave Man

    Joined:
    Aug 29, 2008
    Oddometer:
    453
    Location:
    Northern New Mexico
    Indy was right. The top shock eye was badly ovallized. Actually more like a bow-tie profile, if you imagined the bore in a longitudinal section view. I believe this was caused by the bending of the top mount bolt. When I re-fit the shock after RaceTech re-built it, I fit a new straight bolt, but the original one had bent, and now, the new bolt has bent at least as badly. Time to re-engineer what BMW hath wrought.

    I am thinking the reason I could not detect this at the rear wheel with the bike on the centerstand was that there was enough lateral pressure from the bolt to bind the shock eye end to end so my feeble efforts to raise the wheel and feel for some slop were not enough to shift the eye on the bolt. Going down the road it knocked horribly though. I hadn't ridden the bike in a while due to snow & ice on the driveway, but when the truck starter failed I needed to get the bike out and was shocked (ha) how bad it had gotten. Ride it every day and you slowly get used to problems. Take a break from riding and experience the problem fresh and it can be surprising what you were putting up with.