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Thread: '88 K100LT Fork Seal Replacement

  1. #1
    Route 66 Missouri gstom's Avatar
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    '88 K100LT Fork Seal Replacement

    I have been studying my Clymer Manual to see how to simply replace the fork seals on my K-bike. The procedure in that manual involves a complete removal from the triple tree and dis-assembly of the forks.

    Am I wrong, or can one simply remove the front wheel, fender, and brake calipers , then take out the allen head bolt at the bottom of the fork slider, then pull the slider down from the tube?
    Once the slider is removed, the seal can be replaced and the slider re-installed onto the tube, the allen head bolt installed and tightened?

    Thanks for any input . I obviously have never done this before on a K-bike.

  2. #2
    GSer JERRY's Avatar
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    Tom,
    it's been years but that's the way i did it on a K75, i'm sure you're right.
    also i recall my dealer cautioning me to have a sharp (new) allen driver as that bolt head in the fork has a shallow head and you don't want to round it out.
    had no problems and i'm not much of a mechanic.
    do you have a fork brace? should be loosened and retighten after.
    jerry

  3. #3
    Registered User kioolt's Avatar
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    That's how I did it on my 91 K100LT. Sometime the Clymer manuals will have you remove a lot more than necessary. I once put a clutch in my 82 R100RT by following the Clymer manual. After I got it all apart I wondered why they had me remove some of the parts they did.
    2004 R1150RT 151,500 miles , 1991 K100LT 128,000 miles, 1982 R100RT 106,900 miles
    Total 386,400 BMW miles
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    A bozo on the bus deilenberger's Avatar
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    Originally posted by jerry
    Tom,
    it's been years but that's the way i did it on a K75, i'm sure you're right.
    also i recall my dealer cautioning me to have a sharp (new) allen driver as that bolt head in the fork has a shallow head and you don't want to round it out.
    had no problems and i'm not much of a mechanic.
    do you have a fork brace? should be loosened and retighten after.
    jerry
    While it could be done that way.. it probably won't be the first time you do it..

    Problems with the allen bolts are several:

    1. It is usually WAY overtorqued. Mechanics see a bolt head that size and decide it should be REAL tight. It only has to be tight enough to crush the aluminum crush washer under it.. which is about 10-15 Ft/Lbs.. so usually it's overtightened.

    2. It usually has corroded a bit - making it even harder to get out.

    3. It's a very difficult position to put enough force on to keep the allen wrench in the allen socket.

    4. It's made out of aluminum - not steel. So they're real soft.

    ------------------------------------------------------------------------------

    My prediction - the first time you do this you're gonna bugger up the allen recess in it and end up taking the fork tubes out of the triple-clamps anyway.

    ------------------------------------------------------------------------------

    My suggestion - look at the job.

    It is very little more work to remove the entire tube with slider than it is to just remove the sliders. By the time you have everything off to remove the sliders - it's just the 4 triple-clamp bolts that need loosening.

    Once the fork tubes/sliders are off - there is a vague chance you can get the allen bolts out if you mount the slider in a vice (padded) and use an allen driver in a 3/8" ratchet.

    If not - no loss - 'cause before you do the job you should invest in two new bolts and the crush washers under them. IF you have them - chances are you won't need them. If you don't - I can about guarantee that you WILL need them. BTDT many times.

    Once the allen-recess is boogered (tech-term) - get out your electric drill and a 1/2" bit (a bit smaller will also work) and drill the heads off the allens. This is lots easier than it sounds - the allen recess guides the drill very nicely and the aluminum is soft.

    Once the heads are off - you can easily pull the sliders off and unscrew the remaining threaded stub with your fingers (no force holding it on).

    ------------------------------------------------------------------------------
    On reassembly:

    1. DON'T overtighten the slider bolts. THINK about the design - once the axle is in there - they can't come out. They are special bolts and the torque spec on them is LOW. You only need to feel the crush washer 'crush' and they're tight enough.

    2. REPLACE the crush washers. They're one time use - and you don't want fork oil dribbling on your rotors.

    3. Replace the tubes in the clamps - and ONLY tighten the top clamping bolts. Then reassemble loosely the rest of the front end (wheel in place - axle ONLY held in with the center bolt on left side of the bike..) and take the bike off the centerstand and whatever you're using to hold it up.

    4. Now tighten from the top down (the reason for #3)...

    The top triple clamp bolts are tightened..

    Now get on the bike, grab the front brake and BOUNCE BOUNCE BOUNCE the front end.

    If you can find a fat friend to do the bouncing - it helps a lot - 'cause they can hold the front forks compressed while you're tightening.

    After the first set of bounces - tighten the bottom triple-clamp bolts.

    BOUNCE BOUNCE BOUNCE - again. If you have a fork brace (or the brace used with the 2 piece fender) - tighten this next.

    BOUNCE BOUNCE BOUNCE - and tighten the clamping bolts on the left slider for the axle. (You DID tighten the center bolt in step #3 right?

    BOUNCE BOUNCE BOUNCE - and tighten the right side slider axle clamp bolts.

    What you're doing is aligning the fork tubes - if you don't do this correctly you are going to have a binding front end. It will wear quickly and you'll know it 'cause of the bashing you'll take over bumps.

    When you're all done - go over every bolt with your torque wrench - and after checking them - mark each one with a dab of touchup paint (Ever wonder what the green dots on critical bolts from the factory were for? That's what.. it's called quality control.. and you don't want your front end falling apart.) One they're marked - you KNOW you've checked them and they're tight.

    That's about it. Takes about as long to do it as to give the directions.. (almost..)

    DISCLAIMER: You may be a complete moooroon.. and shouldn't be given a wrench to save your life. The above is what I do - not what I'd recommend YOU do. If you asked me to recommend that you do something I'd recommend you take it to the dealer so you can't sue me..
    Don Eilenberger http://www.eilenberger.net
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  5. #5
    Route 66 Missouri gstom's Avatar
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    Seal Replacement

    Don, you have provided some excellent words of wisdom on performing this job. Your description is much clearer than the Clymer manual, even without the photos.
    I did the seal replacement last weekend using the simplified version (not removing the fork tubes) Fortunately the bottom bolts both came out very nicely and the job went smoothly. I can see now that removing the forks from the triple tree would really add only a couple of minutes to the overall job, and instead of plopped on the cold concrete floor I could have been standing at the workbench in front of the heater

  6. #6
    A bozo on the bus deilenberger's Avatar
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    Re: Seal Replacement

    Originally posted by GS Tom

    Don, you have provided some excellent words of wisdom on performing this job. Your description is much clearer than the Clymer manual, even without the photos.
    I did the seal replacement last weekend using the simplified version (not removing the fork tubes) Fortunately the bottom bolts both came out very nicely and the job went smoothly. I can see now that removing the forks from the triple tree would really add only a couple of minutes to the overall job, and instead of plopped on the cold concrete floor I could have been standing at the workbench in front of the heater
    Tom - thanks. After doing a bunch'a these (my original K100RT kept loosing one fork seal until I bought a spare set of forks - then it stopped.. (Eilenberger's Law of Spare Parts).. You realize that what looks harder (removing the fork legs) is actually easier.

    It is especially easier if you're thinking of giving the forks a good flush and change of fluid, combined perhaps wth new springs.

    Once they're off the bike - they are really easy to work on..

    Best,
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  7. #7
    ABC,AMA(LIFE),MOA,RA,IBMW MANICMECHANIC's Avatar
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    It also a lot easier, when doing the flush of the slider and tubes, to use some brake cleaner to get rid of all the grunge(technical term) that will be residing in the bottom of the sliders. Also helps to clean up all the parts and fasteners. The downside is that now the rest of the bike needs a good cleaning.
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