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Thread: 1978 R100S, Odd noise from right cylinder head

  1. #16
    Registered User lmo1131's Avatar
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    Jan 2010
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    I'll try that. I just figgered that the braiding would keep the rubber for disintegrating; may the braiding is what's causing the abrasion (?)
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  2. #17
    Monza Blue 1974 R90/6
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    In my case, with the tension of the curved choke cable pressing against the back of the petcock, the internal metal casing of the choke cable first vibrated it's way through the plastic outer cover of the choke cable and then metal to metal, started chewing it's way into the petcock. The spiral steel winding makes a great saw.

    Barron

  3. #18
    Registered User
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    Hope everyone had a great Memorial Day weekend- I meant to post this sooner but between Memorial day and other happenings...

    Anyway, heres what I found in my case: Red arrow is where fuel tank seam was rubbing on the right horn strap bolt.

    My Dad recently borrowed my uncles 1978 R100/7. Both his bike and my '78 R100S have exact same Luftmeister fairing setup, so I was comparing mounting positions. What I found raised another question for me- the R100/7 does not have the spacer(indicated by blue arrow) and its horn straps are aimed downward(simulated by yellow arrow) and horns positioned appropriately. As a result the strap and bolt are much further in and nowhere near rubbing on the tank like mine is. Also, with this setup the horn straps are also rubbing on the frame. At this point I'm thinking I'll remove the spacers and get shorter bolts and re-aim the horn mount straps like they are on my uncles /7.

    Is this spacer part of the stock R100S fairing setup?
    BMW_horn_bolt.jpg
    1978 R100S Smoke Red Metallic

  4. #19
    Administrator 20774's Avatar
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    So you have a full Luftmeister fairing on the R100S as opposed to any smaller bikini fairing? I have a Luftmeister on my /7 and don't think I have any kind of mounting bolt like that. The picture is a bit close in to tell exactly where you're looking. The fairing sits as a shell sits on top of a metal frame, held to the metal frame by two small bolts on either side. The fairing frame is held to the bike's frame by a set of hose clamps, one each on the forward frame downtube and one clamp on the cross member between the two downtubes. I have dual Fiamm horns which IIRC are connected to welded eyes on either side of the frame. I have a metal bar that connects on one end to the eye and the horn attaches to the other end of the bar. I think the bar does two things...extends the horn away from the frame and also provides for something to vibrate when the horn is use...I think the horn sound/vibration couples with the resonance of the metal bar.
    Kurt -- Forum Administrator ---> 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!

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