Motor mount studs shearing

Discussion in 'General Questions' started by Slaz, Aug 4, 2014.

  1. Slaz

    Slaz New Member

    I built my bike about a week and a half ago and ever since then I have had problems with bonds shearing. I drilled out and replaced the ones on my exhaust but the ones on my back motor mount keep coming out or shearing off. I replaced the studs with new hardware and it still sheared. I am using the aluminum spacer that came with my seahawk motor and its shearing right at the engine. Is there a way to stop these bolts from breaking? I tried to use locktite
     

  2. butre

    butre Well-Known Member

    use automotive grade studs from an auto parts store. the ones you get at home depot and the like aren't very good, and the ones that come with the engine are even worse.
     
  3. Slaz

    Slaz New Member

    I just ordered 2 5/16ths grade 8 studs and I'm just going to tap them out to that because a metric stud that's 10.9 grade and is long enough is impossible to find. I'm also thinking about Jb welding them into the engine. Is this a good idea?
     
  4. butre

    butre Well-Known Member

    There are plenty of people who jb weld their studs in. it works well, it's probably better than the normal methods.
     
  5. Slaz

    Slaz New Member

    As long as it is grade 8 it is unlikely to shear off... Right?
     
  6. butre

    butre Well-Known Member

    I've got grade 8s in mine and they haven't sheared
     
  7. crassius

    crassius Well-Known Member

    I'd guess your mount is horribly wrong and you are over-tightening them to compensate. Hard to tell tho without a pic. I buy 6x1.0 threaded rod at 8.8 to cut my own studs when I do a bike for someone that is the type to over-tighten things. Loc-tite or jbweld will just cause problems when replacing. If all else fails, and customer keeps breaking them, I use an old 8x1.25 head stud cut down about an inch & 1/2 shorter, re-threaded the full length & heli-coiled into the back mount. So far none of the ham-fisted guys has been able to break one.
     
  8. butre

    butre Well-Known Member

    My mount is as right as it can get, My frame didn't give me the best angle to work with. I never had problems with shearing though, I had to replace the studs right away because the stock ones weren't long enough to clear the oval shaped downtube on my bike.
     
  9. Fabian

    Fabian Well-Known Member

    I also have never had problems with studs shearing in half, and that's in 35,000 miles of riding, where for the most part the engine works it's guts out.
     
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