Stripped Exhaust Threads

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

  1. Plaka

    Plaka Brevis illi vita est

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    #21
  2. Paul_Rochdale

    Paul_Rochdale Been here awhile

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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".

    They are obvious when the nuts are seized on. They should be saying to themselves "Hey, this ain't right. Let's ask someone or lets read up about it". Don't just go hammering away or heaving on the correct spanner until damage is done. It's their time and money that's getting wasted not mine.

    And what "frailties" would that be? :huh
    #22
  3. hensmen

    hensmen Been here awhile

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    Sorry Plaka, i don`t know what you mean.
    On my picture can you see how this functiones. You have two halfcircles and one ring and you connect the halfcircles on the cylinder and the ringover it.
    Connected all with four normal screws and fits to the worsest" exhaust-damage".
    Have it on my winterhack since years and it is great.
    Hans
    #23
  4. Jim Day

    Jim Day full manic mechanic

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    The OPs bike predates the internet by decades and from the looks of it was probably damaged long before he ever bought it.

    Take a look at the pics that's probably not stripped threads you're looking at but broken loose high temp epoxy. If he cut the nut off it would probably look exactly the same.

    Ultimately with any mechanical device certain problems come up, and the possible mechanical mistakes or issues involved can in fact get repeated over and over by isolated people all over the world.

    I'm a new poster here but a veteran poster on other boards with other mechanical discussions.

    The web is a great resource, so are these boards.

    People can come here and figure out how things are done from looking at the past experiences of others, but you can't expect everyone to know what has been posted before, or essentially the boards status quo.

    It's easy to say: "Why don't these people know this" when they post something that seems to have an obvious answer, but I like to keep in mind that even if it's something I've talked about a million times it is new to them.
    #24
  5. Jim Day

    Jim Day full manic mechanic

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    I'd love to have one of those. Welding the metal on is easy, getting that die might be more difficult. It would be hard to justify the expense for something I'd hardly ever use but it would be nice to have around. If you ever see one at that price again PM me.

    Anyone know the exact specifications for the the threads?
    #25
  6. Jim Day

    Jim Day full manic mechanic

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    Yes I think it could be done that way.

    If you go the welding route (I can weld)

    One way would be to weld material directly on it, build up a surface then cut the threads with a die specifically made for it, but you'd have to get your hands on a die.

    Another way would be to machine the threaded portion cut it back then tig weld the threaded portion in place.

    Of the two that sounds more drastic but really it's not. Building up the surface is less technical but it puts a lot more heat into the head do to a longer welding time and more heat transfer. If I was going to do that I'd Mig it with a spool gun, which is faster with less heat exchange.

    I know it's designed to take a lot of heat but when working with aluminum I'm always concerned about heat transfer and potential warpage.

    Tigging a threaded portion on would put less heat into the head, migging it would put even less, and I'd say it's a good option. That's why I asked if anyone had the exact specifications of the threads.

    If someone could get me a section of properly threaded tubing with the right ID, I could have that welded in place and completely repaired in an hour.
    #26
  7. Stan_R80/7

    Stan_R80/7 Beastly Gnarly

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    The exhaust threads on one of my spare /5 heads are are M52x2. The thread dimensions can be calculated using a Machinery's handbook and there are some web pages with this dimensional information. I always wondered how to make a jig for the head to single point thread the exhaust threads in a lathe? I expect someone has figured out a way. I have seen dies for sale on Ebay from Germany for ~$100.00 + shipping.

    Maybe an easier solution is to get a piece of 6061-T6 extruded rod, bore a hole ~39mm in diameter, single point thread the OD to make a threaded nipple, and then cut off the damaged threads on the head and TIG weld on the nipple? The welding raised portion of the new exhaust nipple ID could be line bored in a milling machine or hand filed smooth. Maybe one day I will try this with one of my spare heads, but my TIG welding has to improve first.
    #27
  8. Paul_Rochdale

    Paul_Rochdale Been here awhile

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    The easier solution is when the nuts won't budge, STOP, then use the 'Search' function at the top of the page. OK, OK, I won't mention this again:wink:, for a while at least:wink:
    #28
  9. DK Dan

    DK Dan Been here awhile

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    On a recent tech day a local airhead guru demonstrated an alternative repair technique developed by himself. Unfortunately I did'nt take any photos but the repair can be done with the heads still on the bike. I'm not sure that I got all the details correct but the repair involves the following:

    - a special hollow fixing/guide bush is inserted in the exhaust port
    - a small shaft with a cutting tool mounted is inserted in the hollow fixing/guide bush
    - a hand held electric drilling machine is used to rotate the shaft w. cutting tool at high speed and the damaged thread is removed.
    - a threaded pipe piece is made with the exact same thread type as the original exhaust thread and the threaded pipe piece is mounted on the exhaust port stub.
    - the new thread pipe piece is locked on the exhaust port stub with two small screws and the screw heads are filed off.
    - now you have a new thread installed :D

    Hope my explanation makes sense. I will probably require this repair for one of my exhaust threads and will be sure to get some photos during the process.
    #29
  10. GCCR

    GCCR Been here awhile

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    This is my 11th airhead, and I've never had one do this. Upon closer investigation it appears that it had a repair on it at one time and then someone botched up the replacement. Live and learn.
    #30
  11. GCCR

    GCCR Been here awhile

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    Thanks for the lead. Do you have contact information by any chance.:clap


    Dan
    #31
  12. GCCR

    GCCR Been here awhile

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    Danke, Hans. I will definitely get a set as a backup, and to install for a cross country trip. Terrific product, augezeichnet!

    Dan

    P.S. I'm looking for a reasonably priceed Heinrich tank for a /2 frame. If you come by one that is in very good condition that is available please send me a PM.
    #32
  13. GCCR

    GCCR Been here awhile

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    I'm truly amazed at the knowledge available here on this thread. I'm glad Chris at Boxer Metal referred me here. I'm grateful to all of you for contributing. Many thanks!

    Dan
    #33
  14. d mc gee

    d mc gee Been here awhile

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    #34
  15. Plaka

    Plaka Brevis illi vita est

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    What's to sacrifice? Take care of them and you don't have issues with them. Don't take care of them and you sacrifice them with a hacksaw.
    #35
  16. PaulRS

    PaulRS Dutch fool

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    Use the proper tool, smack it once or twice and undo those nuts by hand.
    If they don't come loose, cut the nuts. Period.

    Than clean threads, fit (new) nuts with anti-seize and repeat this annually, or with every valve-job.
    A little maintenance goes a long way here.

    As for repairing, weld up and re-thread is the proper way, all else is merely a bodge.

    Paul.
    #36
  17. danedg

    danedg Horizontally Opposed

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    You guys are reinventing the wheel here....

    Just send your worn and damaged heads to Randy Long. He's been doing it for years.
    Randy Long
    Long's Mechanical Services
    R.D. 1, Box 685-K
    74 Risbon Road
    Honey Brook PA 19344:deal
    #37
  18. disston

    disston ShadeTreeExpert

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    #38
  19. garthg

    garthg Been here awhile

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    This got me so paranoid, I went out and re-anti-seized my exhaust nuts again.
    #39
  20. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Seconded. A repair like that is as good as new. Too bad the OP's exhaust stub was bodged, but that happens. The annual ritual is to undo the nuts, clean off the threads with a BRASS wire brush, apply Anti-Seize generously and tighten them up. The Book say snug to 109 ft/lbs or so; I do them to a double-grunt.

    --Bill
    #40