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I recently removed my exhaust. When trying to remove the nut on the cylinder head stud, the stud came out. I did not like the condition of the stud or the nut so I am replacing both of them. I referred to the Heavy Maintenance Manual.

In paragraph 3.11.1 (72-00-00) (Cylinder head and exhaust manifold studs), it says to use Loctite 648.

The old stud did not appear to have any or it was so little I cannot see it.

My questions are these:

1). Am I reading the manual correctly and am I suppose to use Loctite 648?

2) If so, how much?

3) I have read that Loctite 648 is a retaining compound but if I every have to remove it again, how difficult is it and what is the best procedure?

Thank you for your help.

Bob
  • Re: 912 ULS Cylinder Head Exhaust Studs

    by » 7 years ago


    You are correct. This was a change. Loctite 648 can be released with heat.


    3.11.1) Cylinder head and exhaust manifold studs
    See Figs. 72-60, 72-61 and 72-62.
    Studs M8 x 20/23 (1) are for attaching the exhaust manifold. Check for
    tight fit and any damage.
    When replacing a stud, it is fitted so that the longer thread (23 mm
    (0.91 in.)) is screwed into the cylinder head. Secure studs with
    LOCTITE 648.
    Tightening torque 8 Nm (70 in.lb)

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: 912 ULS Cylinder Head Exhaust Studs

    by » 7 years ago


    Thank you Roger.


    Bob Dean

  • Re: 912 ULS Cylinder Head Exhaust Studs

    by » 5 years ago


    I’m in this same scenario and found this thread and the corresponding Heavy Maintenance instructions to use Loctite 648. In researching that product though, i found that it has a service temperature max of 300 F. Is this a mistake on BRP Rotax’s part? Surely the exhaust head gets up into the 600’s F if the exhaust pipe is in the 1200+ range. If so wouldn’t that render this product useless? Also, Henkel’s website states that this product should be used when securing round and smooth shanks into a housing like in a press fit application. These studs are threaded, going into a threaded housing. Wouldn’t that call for a high temp thread locker instead?

    I just want to use the right stuff so these don’t back out again.

    Thanks!

  • Re: 912 ULS Cylinder Head Exhaust Studs

    by » 5 years ago


    The head is aluminum and has lots of cooling water flowing through it.
    Contrary to what you would think, the exhaust studs likely never get to 300°F due to all the cooling.
    It has been working this way for years without anyone complaining that the studs coming loose in operation.
    The complaint is usually more like, "How do you get these things to come out!"
    Usually, the external Nut is seized on the stud and they come out as a set. Not a bad outcome.
    If they were tight until you intentionally loosened them, there is not really a valid complaint.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.


    Thank you said by: Brian Cass

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