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Broken bolt, broken bolt, broken bolt...

Discussion in 'XJ Technical Chat' started by anachronism, Sep 11, 2016.

  1. anachronism

    anachronism Member

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    I'm starting to get really concerned with how easy bolts are breaking off in my Bike.

    In 3 months of ownership, I've broken 2 exhaust studs, the pinch bolt on the rear tire, and now one of the bolts securing the gauges. They have all snapped with ridiculously low levels of torque applied.

    I've worked on plenty of vintage stuff, but have never seen it this bad. I live in Colorado and generally don't have corrosion issues. I'm aware that dissimilar metals will galvanize together, but they aren't sticking, just snapping like I am twisting matchsticks...
     
    anachronism, Sep 11, 2016
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  2. Toomanybikes

    Toomanybikes Well-Known Member

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    If PO was heavy handed some of those bolts have been over stressed.
    Exhaust studs are one thing that heat and time will weld together. And if the exhaust is aftermarket some owners do not install new gaskets, they just keep cranking on the old ones until they stop leaking
    Good luck with the next thing you take apart:)
     
    Toomanybikes, Sep 12, 2016
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    Jetfixer likes this.
  3. GoCrazy

    GoCrazy Member

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    I am currently rebuilding my 1990 XJ600 and so far I've broken 3 exhaust studs and one pilot screw. Now I am like 95% finished and still wondering what else might go wrong :)
     
    GoCrazy, Sep 12, 2016
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  4. anachronism

    anachronism Member

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    I understand that the exhaust studs are going to be weak as hell given that they are undersized and go through lots of heat cycles- along with welding to the heads due to steel vs. aluminum.

    But, I have no understanding of the other stuff. None of the bolts that are snapping even give me the indication that I am even cranking on them- like 5 ft lbs is twisting a bolt in half...
     
    anachronism, Sep 12, 2016
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  5. Polock

    Polock Well-Known Member

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    don't even try to take a screw or nut off of one of these without putting Kroil or 50/50 ATF/ acetone or lacquer thinner for at least a day
     
    Polock, Sep 12, 2016
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  6. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    ^ Applying pentrating oil is a must.
     
    k-moe, Sep 12, 2016
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  7. anachronism

    anachronism Member

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    I think I'll have to make that SOP.

    I also think I'm wanting to replace basically every bolt I remove.
     
    anachronism, Sep 12, 2016
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  8. GoCrazy

    GoCrazy Member

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    Remember to use loctite/ right type of grease. Speaking of studs, I used a ceramic grease (up to 1200 Celsius degrees) which is also recommended for ABS and oxygen (lambda) sensors. Beware of copper grease in case of steel studs - steel + copper + aluminum = bad combination :)
     
    GoCrazy, Sep 13, 2016
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  9. jmilliken

    jmilliken Well-Known Member

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    PO could have used threadlocker on everything?

    Penetrating oil is a must
     
    jmilliken, Sep 13, 2016
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  10. Jetfixer

    Jetfixer Well-Known Member

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    Either that or Moose Cholock got real crazy over torqueing EVERYTHING... I use Locktite never seize all we used on the aircraft !! You cussed the last guy who did not put it the borescope inspection plugs ....broke more extension and swivels than I can count removing these on CFM-56 and CF-6, CF34-8 and PW2000/4056 sorry just remising , since I went to management I don't get my hands dirty like I used to 30 yeas have flew by.
     
    Jetfixer, Sep 13, 2016
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  11. anachronism

    anachronism Member

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    No. It isn't so much that the bolts are stuck as it is that they seem ridiculously weak. Twisting apart with almost no torque...
     
    anachronism, Sep 14, 2016
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  12. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    That is on purpose. The Japanese developed their fastener standards with a severe materials shortage to deal with. It's much less expensive to have a fastener fail and then extract it than to damage a machined casting.
     
    k-moe, Sep 14, 2016
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  13. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Interesting, where did you learn about that?
     
    chacal, Sep 15, 2016
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  14. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    I don't have a specific point-source for that information. It's just what's been relayed to me by a few machinists and engineers that I know.
     
    k-moe, Sep 15, 2016
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  15. Polock

    Polock Well-Known Member

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    i'm sorry but that makes no sense in so many ways
     
    Polock, Sep 15, 2016
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  16. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    It really does make sense. Overtorquing a fastener and having threads strip out or a casing crack is big $ if it happens often. Production costs go up when parts break. Remember that the fancy torque-limiting drivers hadn't been invented when the fastener standards used on our bikes were being developed . The U.S. standards addressed the issue by allowing the driver to cam-out of the fastener (I'm specifically thinking about Phillips head screws). The Japanese took a different route. Both have advantages and disadvanages. Both lead to the same goal; keeping the expensive parts from turning into scrap on the assembly line.

    Now, whether or not what I've been told is the whole story or not; that I can't say.
     
    Last edited: Sep 15, 2016
    k-moe, Sep 15, 2016
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  17. Polock

    Polock Well-Known Member

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    steel in the 80's was so cheap the US mills were shutting down and Japan was selling it for less than it cost to make.
    metric screws are the same today as they were back in the day, and they don't fail but left untouched, in 2050 they will
    it's even cheaper to use a better fastener that won't fail in the first place.
    i bet none of the bolts broke 30 years ago and Yamaha didn't care what happened 30 years in the future
     
    Polock, Sep 16, 2016
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  18. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    So it can be overtorqued by an apprentice assembly line worker, and strip out or crack an engine case that then has to be scrapped?
     
    k-moe, Sep 16, 2016
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