Exhaust Stud Came Off, How To Fix Aluminium...

Discussion in 'Technical Help' started by R. Steady, Apr 15, 2019.

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  1. Wishbone

    Wishbone First Class Member

    Nov 4, 2018
    848
    643
    Essex UK
    Anything to keep us riding cheaply!
    Worst that can happen is it lets go and you get some extra exhaust tone;)
     
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  2. Arudge

    Arudge Member

    Apr 3, 2019
    48
    18
    Cradley Heath
    +1
    The only way to repair this is to weld repair it.

    In theory there should be another 10mm of aluminium behind where the drilling ends, so you could try drilling and tapping deeper. Right now its scrap so you can't make it any worse.

    If you can get the head to me, I can weld, re drill and tap it for you. But the head will need to be stripped because we have to pre heat aluminium prior to welding.

    Either that or it's a replacement head from a breakers.
     
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  3. Arudge

    Arudge Member

    Apr 3, 2019
    48
    18
    Cradley Heath
    You don't have enough threads left to try this, you would need to drill deeper and tap deeper.

    Ideally you need at least 1.5 × the thread diameter deep, so an 8mm stud should be in 12mm. At the very least you want 8mm of thread depth.
     
  4. feckless

    feckless Noble Member

    Apr 16, 2019
    957
    443
    Cumbria
    if you are not going to remove the head why not try and use the Kwiksteel epoxy putty. just force into the hole and build it up to how it was before. then drill & tap it. if it doesn't work you have lost nothing other than time. if it does work you have a result.
    I have used the stuff on few jobs and found it very effective.
     
  5. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,441
    1,000
    Norfolk UK
    Any chemical metal will crack due to differing expansion and contraction the only way is to weld and re drill/tap.
     
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  6. Arudge

    Arudge Member

    Apr 3, 2019
    48
    18
    Cradley Heath
    That section has torn clean off, if you look closely at the break you can see how crystalline the metal is, I'd challenge the material they cast it out of in the first place.

    I've no idea where triumph source their parts, but the stuff we see coming out of China can range from laughable to downright dangerous.

    If a supplier can use something cheaper and they think they can get away with it, they will.
     
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  7. Eldon

    Eldon Elite Member

    Nov 14, 2018
    1,884
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    North Yorkshire
    Not necessarily so....

    Back in the 90s I tig welded a number of Ali heads for a friend's business. They ranged across multiple brands. BMW was definitely by far the worst, I think they'd melted old saucepans or something. Nissan in comparison was excellent clean material of a far superior melt.

    As I mentioned previously chemical metal is not appropriate for this repair.
     
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  8. Arudge

    Arudge Member

    Apr 3, 2019
    48
    18
    Cradley Heath
    Not exactly sure which bit of my post your challenging, and all challenges are welcome, but I couldn't agree more regards your statement that quality is brand specific. And the Japanese are still regarded the best for quality, certainly in tooling, which is what I do.

    A previous employer did work for Triumph a number of years ago, but the parts were cast in India, that didn't end well either.
     
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  9. Eldon

    Eldon Elite Member

    Nov 14, 2018
    1,884
    800
    North Yorkshire
    #29 Eldon, Apr 24, 2019
    Last edited: Apr 24, 2019
    Arudge I agree on the crystalline appearance as I commented on this in one of my earlier posts but.... assuming its the original, the casting is at least 22 years old so hardly a poor casting from dubious material: don't you agree?

    I'm not sure the country of origin is totally the answer either as rubbish (and good stuff) is made all over.

    The actual fitting of the current and/or previous exhaust studs plus possible previous over tightening of the exhaust manifolds to resolve leaks rather than fitting new gaskets etc. stressing an area subject to expansion and contraction is never a good combination.
     
  10. Arudge

    Arudge Member

    Apr 3, 2019
    48
    18
    Cradley Heath
    Hello Eldon.
    It's not the quality of the casting itself, but the material they cast.

    The bit that bothering me is that the boss was large enough to take the load, and the threads should have failed first, yet the whole front came away.
    And the OP was told this has been seen beforeo_Oo_O.

    I havn't worked with gravity castings since the 90's, when most heads and blocks were cast from LM11. I've sawn countless casings up to check section thickness and sand core locations, the material never had a granular appearance like that. That's why I'm wondering if the original casting material was up to spec.

    I'm sorry for sounding so sceptical but I make my living repairing stuff that should never have failed, but more often than not the failure occurred because somebody tried to cheat/save money/use inferior materials. You've go to see it to believe it!! The worst culprits are India and China, but their so cheap!!

    I know some of triumphs castings came from India because an ex employer was the supplier, but I don't know what they supplied nor when.
     
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  11. Eldon

    Eldon Elite Member

    Nov 14, 2018
    1,884
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    Yes fair comments Arudge and i think we agree on most of the technical points.
    I'm also of a cynical and sceptical nature so for something to last 22 years then fail something has changed.

    OP, did the old studs come out easily or were they seized?

    Has an anti clockwise strain initiated a fracture within the casting so that when compounded with a clockwise strain the casting failed.
     
  12. Eldon

    Eldon Elite Member

    Nov 14, 2018
    1,884
    800
    North Yorkshire
    The old expression in the trade was "boomerang heads" as in so many were warranty failures.
     
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  13. Arudge

    Arudge Member

    Apr 3, 2019
    48
    18
    Cradley Heath
    A very valid point, but given that everything looks so clean, the stud clearly hadn't bottomed out and 'jacked the front off' I'd simply say the OP overtightened it, and torque wrenches are so very unreliable. I have three calibrated wrenches as none of them can be trusted from one end of the range to the other.

    And neither do I wish to criticise the OP, but it would be interesting to know if the OP felt he may have overtightened the nut regardless of what the torque wrench was telling him. Even so, the casting shouldn't have failed like that, we've all pulled threads out of alu castings, that's what helicoil inserts are for :)
     
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  14. R. Steady

    R. Steady Member

    Dec 14, 2017
    46
    13
    Leiden, Netherlands
    Hi all,

    I've been off the internet for a couple of weeks because of private reasons. I didn't mean to get a quick answer and sod off, that would be rude.
    Thank you foor the replies and discussions. Very interesting.
    If I had a spare bike I would try the pre heat, weld up, drill out route. I discussed this also with a mate who is a precision mechanic, he said the same, pre heat, TIG,drill

    Now I haven't got the time to fix it properly, because next Friday I'm off to France with 4 mates. (Yes, I am insured for a replacement bike when it brakes down.)
    The good news is, I took it for a testride today and all seems ok.

    Thank you all again. Will post pics in build/project thread.

    Tjeerd
     
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  15. R. Steady

    R. Steady Member

    Dec 14, 2017
    46
    13
    Leiden, Netherlands

    Ehm.. OP,... is that me?
     
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  16. Sprinter

    Sprinter Kinigit

    Aug 17, 2014
    6,005
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    original poster
     
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  17. R. Steady

    R. Steady Member

    Dec 14, 2017
    46
    13
    Leiden, Netherlands
    Good point, I think
    When I loosened the header nuts, only the most outside ones came off the studs. The others took the studs with them.
    I had brand new studs laying around an unfinished Ford CVH project so I thought I'd renew them all. Guess maybe not a great idea.

    The far left stud came out with no hassle, On the far right I had to use more force, not excesive, still a spanner and by hand. but it was a lot tighter then the other side. Maybe the anti clockwise strain made it seize.. I'm no expert, but your theorie sounds plausible.

    Tj.
     
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  18. R. Steady

    R. Steady Member

    Dec 14, 2017
    46
    13
    Leiden, Netherlands
    We did 3000+ Km last week and the exhaust is still on.

    Had some orher issues involving black smoke, low rev bogging and poor mileage. I’m guessing worn out emulsion tubes. Never a dull moment..

    Tjeerd

    8C9E42A3-C6CD-48FE-95C9-DADAA3CD238E.jpeg
     
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  19. freck

    freck Elite Member

    May 4, 2017
    1,719
    750
    Preston, Lancs, UK
    #39 freck, May 20, 2019
    Last edited: May 20, 2019
    That’s an interesting collection of bikes. Liking the Falco cafe racer. :grinning: Hope you had a great trip.
     
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  20. R. Steady

    R. Steady Member

    Dec 14, 2017
    46
    13
    Leiden, Netherlands
    I agree, the Falco is insane!
    Trip was great, French Gard/Ardèche has endless curves.
     
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