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Thread: 1988 R100RT - Bent upper shock mount

  1. #1

    1988 R100RT - Bent upper shock mount

    Greetings, very new here so please allow some space for my forum/jargon learning curve. Thankful for this community and all that help. Here it goes...
    After cyber stalking almost every corner of the metric bike internet for about 5 years (move, new city, new job, new kids, etc), the pandemic motivated me to purchase not only my first Airhead but also first bike (1988 R100Rt). With nothing more than a basic rider course under my belt, I trailered home a Craigslist find (didnít know what I was looking at) from Ft Smith, AR, almost 5 hours from my home in the DFW metroplex. Started acquiring tools and doing minimal basic maintenance as the work flow nudged me to get it running. Upon more detailed inspection I noticed the upper shock mount looked crooked. After asking around a bit, come to learn monoshock rubber mount bushings wear after 32 years. Time for a new shock & here I am unwilling to press this new shock onto the 2nd mounting bolt. Something is not right & need some advice from people who have/can work with metal. Attachment 79841Attachment 79842

    Thanks in advance for any advice for suggestions on how to proceed!
    Attached Images Attached Images
    Reils
    88 R100RT
    Rockwall, TX

  2. #2
    Liaison 20774's Avatar
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    Reils -

    Welcome to the forum! I'm guessing you haven't been out on the bike yet. I'm not familiar with the mono shock model in terms of how the upper mount connects to the frame as well as what it connects across to the other side. Is there observed bends/creases in the right side frame ahead of the shock mount? If the frame is bent, then there must have been some major pothole hit at some point. Seems like someone who has experience with frames would know if it can simply be bent back to normal and/or if there's anyway to add structure to the frame to support it. I suspect that this has weakened the frame and without a proper fix, there's a chance it could break completely creating a hazardous riding situation.

    Maybe you can show a few more pictures of other parts of the frame forward/below the upper mount so we might have a better idea of the extent of damage.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Kurt,
    Thanks for the reply. Once I got it running, (Valves adjusted, carbs rebuilt, new starter due to a failed solenoid) in preparation for inspection and registration, I took it for a spin around the block as I started to get into tires and brakes which led me to the rear suspension. I donít see any instances where the frame is bent, only damage I see is where the Left frame bracket attaches to the Left exhaust & scrapes on valve cover. Guessing youíre right, it was a major pot hole causing the upper mounting bracket to flare out to the right because if it were laid down on its left hard enough to somehow bend the upper shock mount right, the original swing arm would be beyond repair. Iíd love to get an opinion on how to get the bracket squared up without loosing the integrity of the frame. Guessing a hair dryer & hammer arenít gonna get it done!
    Iíll post some more pics then defer to the experts. Thanks again!5EEBEFA1-0E07-4139-8919-F9C4276304E1.jpeg8680FCDC-417B-4236-803E-043762A02A74.jpegDE744261-A184-4DEA-9475-DDFE377CF9AE.jpeg85AED943-79ED-415C-B2EB-0E662D06056B.jpegEC57F7D6-A03D-4EF9-A9FF-23A74DE3F234.jpeg2265AA52-7D33-4FC4-A554-1C6D52D79605.jpeg031EBB4B-DA46-4BDD-BA34-65C839543047.jpegAD5056D7-4925-47AE-8859-82D5A87E31EF.jpeg
    Reils
    88 R100RT
    Rockwall, TX

  4. #4
    Liaison 20774's Avatar
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    Guess it's a little hard to see the details for this. I wonder if you shouldn't tap into the DFW Airhead crowd to get some eyeballs on this as well as get some suggestions. You could join the Airheads Beemer Club and then get a chance to contact other members in your region, even attend a TechDay although I haven't seen/heard of any Texas TechDays in a long time. In my signature line, the link provides a number of resources. There is a frame section and I believe there are some frame companies but they might all be on the west coast. Ted Porter in NorCal and Tom Cutter near Philadelphia are good resources...Anton Largiader in Virginia has a wealth of experience, too. All of those are miles away!

    But checking with your local community would be more helpful. Also in the link is a link to "Airhead Friendly" shops...the list might be a bit dated, but you might see some shops with experience where you could begin asking questions.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
    Compare the top of the old shock and the new shock and see if there is any difference? The old shock might have had a ball joint type swivel at the top.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  6. #6
    Thanks Paul, that makes perfect sense & would be ideal opposed to what Iím dreading. Unfortunately both shocks standard straight rods & loops with rubber mount bushing onto the fit pin. My 1st pictures show the mount of the new shock and 2nd post has pics of the old shock. Again, Iím a total newbie so please let me know if Iím not seeing something right.... my understanding is that during installation, both pins should fit into the new shock simultaneously rather than inserting one then pressing the opposite side & stressing the rubber mount for a crooked fit. Iíve been unable to find any pictures of a monoshock installed. Boxer2valveís ď1985 on R80Ē YouTube video showed it slipping right on cleanly as was expecting. Appreciate all thought, ideas or possible solutions!
    Reils
    88 R100RT
    Rockwall, TX

  7. #7
    Liaison 20774's Avatar
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    Maybe someone with a similar bike who has access to this location could take a picture of a "known good" condition. So nothing connects the left-right side of the frame at this point?
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  8. #8
    6F6F82C5-261C-4B04-940E-0183811D3B49.jpeg
    I removed the battery tray for a more clear picture. Yellow is the welded piece of the frame that I believe has been flared out. As Iím typing I just realized the subframe probably has the nearest horizontal brace, which is broken at the weld! F379E1D5-6C50-45A3-A5DE-82A8A040FC44.jpeg
    Doubtful this is coincidental.
    Thanks again & will gladly welcome any ideas/suggestions (other than ME stripping it all down and mailing to NorCal)!
    Reils
    88 R100RT
    Rockwall, TX

  9. #9
    Registered User 6322's Avatar
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    Not as familiar with the '80s monoshock airheads, but could the top shock mount actually mount inside of the frame versus outside? It's hard to believe it could be that far out of alignment. Also, I've seen the cross brace fractured on several airheads, not from some catastrophic incident. Sometimes from altering the seat or seat mount or from overloading. Good luck with your project. Hope you're on the road soon.
    gp
    Gary Phillips - #6322
    Wildland Firefighter, Retired, Riggins, ID
    Heartland Moto Locos BMW Riders
    '77 R100/7 Dirt Hack, '83 R80ST, '85 K100RS w/EML, '93 K1100LT, '00 R1100RS

  10. #10
    Registered User Anyname's Avatar
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    I have an 86 Monoshock airhead and I just went out and took a look at the upper rear shock mount. First thing, my shock mounting bolt goes from the inside through the frame bracket out to the shock. The nut securing the shock is on the outside. I don't know if this is correct since the pictures on BMWs fiche seem to imply it should go from the outside in. I will say that having the bolt head on the inside allows better clearance when pulling the battery. Also, I noticed that the fiche implies that the lower mount nut is on the inside as well and that's just not possible.

    The fiche picture implies that the shoulder on the bolt is the same size where it goes through the shock eye and the frame shock mount. Is this true for your mounting bolt? Is it correct to assume that your bolt is straight?

    I installed the shock on mine long enough ago so I don't remember anything except it was a tight fit. It does not appear to have a ball joint at the top though.

    The photos of your new shock make it look like it won't align with the lower mount. The photos of the old shock look like it does. Are the upper eyelets of the same construction and alignment?
    BMW R bike rider, horizontally opposed to everything...

  11. #11
    Quote Originally Posted by 6322 View Post
    Not as familiar with the '80s monoshock airheads, but could the top shock mount actually mount inside of the frame versus outside? It's hard to believe it could be that far out of alignment. Also, I've seen the cross brace fractured on several airheads, not from some catastrophic incident. Sometimes from altering the seat or seat mount or from overloading. Good luck with your project. Hope you're on the road soon.
    gp
    Thanks Gary, I removed the shock from the outside of the mount, also all the Fiche show it mounting on the outside. This saga and my obsession continues!
    Reils
    88 R100RT
    Rockwall, TX

  12. #12
    Quote Originally Posted by Anyname View Post
    I have an 86 Monoshock airhead and I just went out and took a look at the upper rear shock mount. First thing, my shock mounting bolt goes from the inside through the frame bracket out to the shock. The nut securing the shock is on the outside. I don't know if this is correct since the pictures on BMWs fiche seem to imply it should go from the outside in. I will say that having the bolt head on the inside allows better clearance when pulling the battery. Also, I noticed that the fiche implies that the lower mount nut is on the inside as well and that's just not possible.

    The fiche picture implies that the shoulder on the bolt is the same size where it goes through the shock eye and the frame shock mount. Is this true for your mounting bolt? Is it correct to assume that your bolt is straight?

    I installed the shock on mine long enough ago so I don't remember anything except it was a tight fit. It does not appear to have a ball joint at the top though.

    The photos of your new shock make it look like it won't align with the lower mount. The photos of the old shock look like it does. Are the upper eyelets of the same construction and alignment?
    Anyname,
    Just looked at the fiche again, you’re right, clearly incorrect for the lower threaded bolt is fitted in the differential housing, so clearly the nut goes to the outside.
    Amazingly both mounting bolts are straight. I noticed the issue when the rubber mount bushings were oozing 32 yo rubber from being so stressed. What I can clearly see & I’m not sure how easy it is to see in my previous pictures, the frame’s upper shock mount is curved about 5mm toward the Right/outside causing the poor alignment 410mm away at the lower mount. Is there any way to shoot a very “internet elusive” picture of your frame’s upper shock mount so I might be able to confirm mine Is bent rather than continue to wonder if my swingarm is crooked?
    The old and new eyelets are the same dimension. They look different in the pics because I at one point pressed the old rubber mounts out of the old shock to replace with new ones, thinking that would fix the problem. Didn’t fix it and cost me a few days building a press tool that ended up mushrooming the new rubber mount. Live and learn. Thanks for your help, and a picture of your frame mount would lead me in the right direction with how to proceed. Thanks!
    Reils
    88 R100RT
    Rockwall, TX

  13. #13
    Registered User Anyname's Avatar
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    Photos of monoshock upper mount:

    IMG_2304.jpegIMG_2305.jpegIMG_2306.jpegIMG_2307.jpegIMG_2308.jpeg

    I don't know if these will help. It's really hard to get a useful view.

    It does look like your mount, frame or both may be bent. I have to wonder how that could happen, especially given the thickness of the cast mount and the fact it's attached at a bend in the frame. That should be a very stiff location.
    BMW R bike rider, horizontally opposed to everything...

  14. #14
    Quote Originally Posted by Anyname View Post
    Photos of monoshock upper mount:
    I don't know if these will help. It's really hard to get a useful view.

    It does look like your mount, frame or both may be bent. I have to wonder how that could happen, especially given the thickness of the cast mount and the fact it's attached at a bend in the frame. That should be a very stiff location.
    Any,
    Thank you!!! It appears clear to me that your monoshock frame mount is straight while mine has a subtle yet significant bend (approximately 5mm). Seems as though my options are now to somehow straighten it or find a replacement frame. Still open for any ideas/solutions. Thank you!
    Reils
    88 R100RT
    Rockwall, TX

  15. #15
    Registered User Anyname's Avatar
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    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.
    BMW R bike rider, horizontally opposed to everything...

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