Stripped Exhaust Threads

Discussion in 'Airheads' started by GCCR, Apr 1, 2013.

  1. GCCR

    GCCR Been here awhile

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    Newbie here. Just started a teardown on a 82 R65. I was in the process of removing the exhaust nuts that were on pretty snug. I shot it with PBR to break them loose. But after a while, when nuts were removed I noticed the threads on the right cylinder were all but gone. Any tips on repairing them? Thanks.


    GCCR
    #1
  2. Warin

    Warin Retired

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    #2
  3. batoutoflahonda

    batoutoflahonda Long timer

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  4. Plaka

    Plaka Brevis illi vita est

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    Talk to Carl...around here somewhere.
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  5. d mc gee

    d mc gee Been here awhile

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    PBR is a "social lubricant", it is a very poor lubricant other wise. Except the next morning.:lol3

    [​IMG]
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  6. Kt-88

    Kt-88 I like everything.

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    Ha!
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  7. Jim Day

    Jim Day full manic mechanic

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    There are a few ways to repair this. Can you post some pics so we can see how bad it is. Where are you located, are there any good metal fabricators or machine shops in your area?
    #7
  8. Jim Day

    Jim Day full manic mechanic

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    [​IMG]
    You have to respect the elegance and ingenuity of Walter's solution, but though I personally love it, I find his adapter to be well kinda.... Well..... ugly on the bike.

    In itself off the bike it's beautiful, on the bike not so much as it doesn't match, looks small and stuck on. A 10 for it's direct simplicity and effectiveness, 6 for aesthetics as they simply do not match the aesthetics of the engine.

    That said.... If I was going to go that route, I'd use his connection at the head but then I'd take the original exhaust port nut, cut the threaded portion off weld in some metal on each side between the fins and drill it to match his attachment flange.

    I know everyone can't weld aluminum like I can but you should be able to find a shop that can do this.

    Essentially you could still use his clamp at the head, but couple it to a finned flange that works the same way but matches the original exhaust nut configuration.

    It' would be like a custom BMW version of a the old KZ Kawa exhaust clamp.
    [​IMG]

    Or essentially like this one I just Photoshopped:
    [​IMG]

    Easy enough to make and it would match the other side.
    #8
  9. GCCR

    GCCR Been here awhile

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    Very nicely done!:clap
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  10. GCCR

    GCCR Been here awhile

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  11. GCCR

    GCCR Been here awhile

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    Hi Jim here are the pics you asked about. I'd be interested in anyone in CA that could repair this.
    [​IMG]

    [​IMG]
    #11
  12. Jim Day

    Jim Day full manic mechanic

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    OK.... You got me thinking, and think I may of just figured out a much cheaper and easier way to do this if there is still some threads at the cylinder.

    Say you take a standard BMW finned exhaust nut.

    [​IMG]

    Then take a hacksaw and cut it completely through on one side, leaving a gap.

    Find a high strength stainless steel exhaust clamp that exactly fits around the non-finned portion of the nut. There are a number of styles to choose from this type would be ideal.
    [​IMG]

    If sized correctly this style would work as well.

    [​IMG]


    Take a triangular file and clean up the threads that are left at the cylinder so there are no large burs or metal that sticks out then coat it with anti-seize.

    Slide your stainless clamp on the nut, slide the nut on your exhaust pipe and hand tighten it in place just like you would normally. Now you want to tighten the clamp around the nut to the point you can no longer turn in by hand, this will effectively reduce the diameter of the nut giving you the maximum thread contact. Put a wrench to the nut and tighten it just enough to get a seal, without stripping or destroying what remains of the threads. Now tighten the clamp tight around the nut to compress and lock it in place.

    Once tightened in place this would hold in place mechanically the same way as Walter's solution, but you wouldn't tighten the pipes connection to the cylinder head further. It might be a little harder to get a good seal, but once you get it, it should work at a fraction of the expense.
    #12
  13. Jim Day

    Jim Day full manic mechanic

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    Ouch!!! That's pretty ugly, and it doesn't look right at all. It looks like it was stripped before and someone used some kind of high temp adhesive on it to get it to hold and seal. That gray gook and stuff with bubbles in it should not be there at all, it's not aluminum.

    In other words you might not of been the one that stripped it.

    I'm in LA.

    I have both a TIG and Mig set up for Aluminum here. I've also have access to a shop in Oxnard.
    I'm not really looking for work but I'd be happy to look at it up close. If you want to bring it by I'm sure we could figure something out.

    Jim
    #13
  14. disston

    disston ShadeTreeExpert

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    You need the proper tool for removing the exhaust flange nut. When using the correct tool if it starts to feel stuck you should feel it and at that point cut the nut off. These threads are to be coated with anti-seize. Many recommend other brands. I use the Permatex, silver one.

    The best repair does seem to be welding new Aluminum and then cutting new threads on the head. This is a really big thread and the die for cutting it is probably not too common. I see the die for sale on Ebay sometimes and it is a $100 I think plus shipping from Germany. I hope you can do this. Maybe there is some other way to cut new threads or the die is not uncommon like I suspect.

    It does look like that head has been repaired before.

    Looks of the two part flange repair aside it does work.
    #14
  15. bmwhacker

    bmwhacker Still on 3 wheels

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    I've removed a LOT of them. I start shooting them with penetrating oil at least a week or so prior to removal attempt. Then use one of the big cast aluminum fin wrenches like you have. Haven't stripped one yet. Maybe just lucky.
    #15
  16. Paul_Rochdale

    Paul_Rochdale Been here awhile

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    Reading about all of these wrecked threads irritates me no end. Why don't riders read up about such things before butchering their bikes? There's endless posts about seized exhaust nuts both here and elsewhere, even videos on YouTube about how to remove them. I've two BeeEms and never had a problem with the exhaust threads. Slice the old ones off if seized, clean up the threads, Copaslip then fit new nuts. Simple.:huh
    #16
  17. Plaka

    Plaka Brevis illi vita est

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    Some things are non-obvious and you don't go researching them. Many are not mechanics and hence are insensitive to a bad thread. if it doesn't come around every so often there isn't current nfo for the newbs to see. What you don't see is the people reading ,getting it right, never posting.

    I remove, clean and lube the nuts at least once a year. no problems here either. letting a connection that gets that hot sit for years is unwise.

    Accept your own frailties and that of others won't bug you so much.
    #17
  18. disston

    disston ShadeTreeExpert

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    Don't take it personal. :D
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  19. isdt BMW

    isdt BMW willserv@aol.com

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    Paul Sturges in Bend Oregon welds and machines for a perfect repair. been using him for 25 years.
    #19
  20. hensmen

    hensmen Been here awhile

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    Hallo GCCR, from Germany i have an alternative, not originalbut it is repaired in a minute and best for adv used bikes. Mean when you travel, i try to put the link:
    http://www.sternmutterersatz.de/
    Don`t know if it is worth shipping but for travelling the eaysiest way.
    Hans from Germany
    #20