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Thread: 1988 R100RT - Bent upper shock mount

  1. #16
    Quote Originally Posted by Anyname View Post
    The thought occurred to me that maybe we can compare measurements between the left and right sides of the frame such as the sub frame mounting points. As best as I can measure without removing the sub-frame, mine is 8 7/8" between the subframe mount points.
    Any, great idea, the measurement between the subframe mounting points is 8 1/8”. That 1/4” is about the difference I expected. Another update... a conversation with and a couple pictures sent to the North Dallas BMW airhead expert who shared with his tech in the shop. Their response was (I’m paraphrasing) - This bend is somewhat normal on monolevers & not much to be concerned with... the rubber mounts in the OEM shock has thicker rubber than some aftermarket shocks, I could either mount what I’ve got or press out and swap the aftermarket shock (yss) rubber mounts with the BMW part.

    I hope I’m not being overly particular with ZERO bike experience, but I’m afraid prying on a brand new shock to fit the bottom mount would create a lateral tension on the shock (yes, the rubber mount would absorb most) that could cause increased wear.

    I’d love to hear from a monolever owner to confirm that this bent frame shock mount is somewhat common.
    Thanks again!
    Reils
    88 R100RT
    Rockwall, TX

  2. #17
    Registered User Anyname's Avatar
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    Hmmm, there are a number of specialist shops listed on Google that straighten motorcycle frames. I also had the kind of depressing thought that the bracket and frame look pretty stout so if that's tweaked, something else may not be straight as well.

    I always fall back on the Max BMW shop in North Hampton for advice on Airhead stuff since they still do a lot of work on them including restorations of old BMWs. They are generally pretty helpful with advice.
    BMW R bike rider, horizontally opposed to everything...

  3. #18
    Quote Originally Posted by reils50 View Post
    Another update... a conversation with and a couple pictures sent to the North Dallas BMW airhead expert who shared with his tech in the shop. Their response was (I’m paraphrasing) - This bend is somewhat normal on monolevers & not much to be concerned with... the rubber mounts in the OEM shock has thicker rubber than some aftermarket shocks, I could either mount what I’ve got or press out and swap the aftermarket shock (yss) rubber mounts with the BMW part.

    I hope I’m not being overly particular with ZERO bike experience, but I’m afraid prying on a brand new shock to fit the bottom mount would create a lateral tension on the shock (yes, the rubber mount would absorb most) that could cause increased wear.

    I’d love to hear from a monolever owner to confirm that this bent frame shock mount is somewhat common.
    Thanks again!

    I have a ‘91 R100 monoshock. The upper rear shock mount is a fairly robust casting that’s welded to the main frame hoop. I wouldn’t believe that the mount is “commonly“ bent without a pretty serious drop or crash—a bit of speculation which may be borne out by your broken sub-frame and MIA fairing. I wouldn’t assume that the bent shock mount and broken sub-frame are the end of the frame damage without a real expert’s eyeball and perhaps some careful measurements in a frame jig. Send your photos to Tom Cutter at the Rubber Chicken Racing Garage for his feedback. No one wants to throw cold water onto an eager new airhead owner, but the reality may be that you’ve bought a parts donor, not a rider.

  4. #19
    Registered User STEVENRANKIN's Avatar
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    Frame measurement

    Having had two airheads involved in major part bending accidents, I agree with the advise to seek a frame shop to have the over all frame checked out before riding. My first bike I hit a deer with resulted in a bent steering head tube on the frame, at the time, the cost to strip the bike have the frame repaired as well as replacing the damaged fork systems, fairing and such was far in excess of what the bike was worth, so it was written off and became a parts donor.

    On the second bike, I was hit by a car from the side. It was stripped down to bare frame which was given to a frame shop. It was evaluated and determined to be all right. From there, I had the bike put back together donor parts and the cost was still higher than the bike is worth. The only reasons, I spent the money to rebuild the second bike was I really liked it and it was a low number model bike. If that had not been the case, I would have purchased a good replacement bike.

    From the pictures and texts, I myself would be Leary with this particular bike. To do that kind of damage is not just a pothole or a bad shock problem. Who knows what else is out of true, I would not like to find out the steering head tube is off center and causing handling problems while riding at any normal highway speed. I do know, this could be a worse case scenario but, it can happen.

    Unless the bike was purchased at a VERY reasonable price, or is something special to the owner, is a very rare model, I myself would not bother anymore than to find another bike in better condition, and part this one out. There are a lot of low mile well cared for bikes on the market.

    Sorry, you had to learn a lesson on what to look for when buying a used airhead. Don't let the experience sour you on them. They are great bikes for what they are and I have never ridden anything but.

    Good luck with what ever you do, I hope you do find a frame shop and it won't cost you a whole packet of money to fix, that would be great if you do, be sure to post the name of the shop. Cheers, St.

  5. #20
    Registered User STEVENRANKIN's Avatar
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    Oh yeah one more thing

    Sorry, just one more thing.

    When my first bike was damaged, my dealer set the bike up in his shop on a level floor and proceeded to use strings, wood doweling and reference marks drawn on the floors and such to check out the damage. No special jig.

    Sadly, this was back at the end of 1984 and of course airheads were still the new bikes. I don't know if a local dealership would have the knowledge as to how to do this, if they still even work on airheads. Not all BMW dealerships do these days.

    St.

  6. #21
    Quote Originally Posted by khittner View Post
    I have a ‘91 R100 monoshock. The upper rear shock mount is a fairly robust casting that’s welded to the main frame hoop. I wouldn’t believe that the mount is “commonly“ bent without a pretty serious drop or crash—a bit of speculation which may be borne out by your broken sub-frame and MIA fairing. I wouldn’t assume that the bent shock mount and broken sub-frame are the end of the frame damage without a real expert’s eyeball and perhaps some careful measurements in a frame jig. Send your photos to Tom Cutter at the Rubber Chicken Racing Garage for his feedback. No one wants to throw cold water onto an eager new airhead owner, but the reality may be that you’ve bought a parts donor, not a rider.
    Khittner,
    Thanks for your insight. My untrained eye has no chance to spot whether or not the rest of the frame looks good. Eager to get on the road while maintaining an clear perspective on reality is definitely the struggle. I’ll shoot Tom a message and post an update if/when I hear back. Thanks again.
    Reils
    88 R100RT
    Rockwall, TX

  7. #22
    Quote Originally Posted by STEVENRANKIN View Post
    From the pictures and texts, I myself would be Leary with this particular bike. To do that kind of damage is not just a pothole or a bad shock problem. Who knows what else is out of true, I would not like to find out the steering head tube is off center and causing handling problems while riding at any normal highway speed. I do know, this could be a worse case scenario but, it can happen.

    Unless the bike was purchased at a VERY reasonable price, or is something special to the owner, is a very rare model, I myself would not bother anymore than to find another bike in better condition, and part this one out. There are a lot of low mile well cared for bikes on the market.

    Sorry, you had to learn a lesson on what to look for when buying a used airhead. Don't let the experience sour you on them. They are great bikes for what they are and I have never ridden anything but.
    Good luck with what ever you do, I hope you do find a frame shop and it won't cost you a whole packet of money to fix, that would be great if you do, be sure to post the name of the shop. Cheers, St.
    Thanks Steve, glad you’re able to share those accidents of the past. These stories will help with my ultimate decision once the estimate gets slid across the desk!
    I paid what I thought was a reasonable price weighing the risk of buying it without much knowledge. However, a donor bike wasn’t on the radar. Figured I’d be ok if there was a major repair or two along the way. I’m gonna optimistically keep both wheels out of the grave but I’ll start browsing the the area for plots.
    Reils
    88 R100RT
    Rockwall, TX

  8. #23
    Registered User cwroady's Avatar
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    My advice is to not give up without at least asking your local BMW shop if they have a frame shop they use, and getting an estimate. It is a good deal of work to strip the bike down and take the frame in, but you might be surprised to find out the cost is not that horrific. I received a quote of $400 recently if one was indeed bent when inquiring locally in SoCal. Bummer for sure, but not enough to accept "parts donor" status for your bike I would guess.
    Chris - 2015 BMW RT / 1973 BMW R75/5 / 1955 BMW R50 - Yard Art - 1968 Hodaka / 1968 Sachs
    SCBMWRC / MOA / Airhead Beemer Club / VBMWMO

  9. #24
    Quote Originally Posted by cwroady View Post
    My advice is to not give up without at least asking your local BMW shop if they have a frame shop they use, and getting an estimate. It is a good deal of work to strip the bike down and take the frame in, but you might be surprised to find out the cost is not that horrific. I received a quote of $400 recently if one was indeed bent when inquiring locally in SoCal. Bummer for sure, but not enough to accept "parts donor" status for your bike I would guess.
    CW, thanks for the encouraging news, ≈$400 and a crash course on electrical my be the solution.

    I emailed Tom Cutter a few pics, his reply is as follows for anyone curious about an expert perspective:

    “Normally that is an issue seen on the MonoLever R100RT models, caused by gross overloading, worn out stock suspension and lots of miles on rough roads. My 1988 R100RS also did that, but that bike was a New York City bike, so I blamed the roads and the fact that the PO was a large guy with a large wife riding pillion.

    The solutions are varied depending on your final goal. If you want a pristine stock bike, then replace the main frame and shock absorber, then follow the published weight limits. If you don't care about stock appearance, strip the bike, straighten the frame and build a cross-support to brace the weakened cast piece.”
    Reils
    88 R100RT
    Rockwall, TX

  10. #25
    Registered User STEVENRANKIN's Avatar
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    Costs

    Of course, if you can do and are willing to do the work involved, the results may be worth it.

    Just because it is a BMW doesn't mean it is worth a lot of money. My first wrecked bike happened in late 84. At the time, there was not a lot of used parts floating around such as the fairing. BMW prices meant the rebuild was more than the bike was worth. Now a days used parts are all over for reasonable prices. I just bought a complete RT fairing and all the fittings for a very good cost. If that option had been available, I would still be riding a 83 R80RT instead of my 84 R80RT. The recently purchased fairing will be used for a 250K mile pretty up job. The original fairing is showing a lot of stress cracks and stuff from over the years.

    I am very happy to read the report from Tom Cutter, I retract my comment about the damage being more than just a worn shock or potholes. I have learned something new. St.

  11. #26
    Reils—Thanks for the update on Cutter’s feedback. Like Steve, I’ve also learned something new, and, hence, decided to skip the fries in tonight’s dinner takeout order.

  12. #27
    Registered User STEVENRANKIN's Avatar
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    Skiping the fries

    I could stand to do a fry skip as well as a pie, root beer, ice cream, and a whole lot of other things. Perhaps then my old leathers would fit again. LOL. St.

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