Balance shaft reinstall

Discussion in 'Mazdaspeed 3/6 Engine' started by jsilva, Jan 12, 2021.

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  1. jsilva

    jsilva Silver Member

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    I happened to come across a thread somewhere saying that reinstalling the balance shaft is not something the average Joe can do, and so a delete is preferable. I’m not sure I want a delete so I was looking up what could be done.

    Has anyone reinstalled it with success?

    I found this:

    https://www.justanswer.com/mazda/6ckhh-mazda-i-installation-procedure-timing.html

    and this:

    https://www.justanswer.com/car/1ymqb-align-balance-shafts-2004-mazda-2-3.html

    I’m assuming it’s the same for the Mazdaspeed engine. Basically it sounds like you set the balance shift wheel thingies to 6 o’clock and the crank at TDC and then install it. The first link provides a document with the official setup for the balance shaft, which is beyond my willingness to pursue. But I’m not sure if that’s necessary for a balance shaft which was already working well in the engine.

    Just wondering if anyone has any thoughts.
     
    jsilva, via an iPhone, Jan 12, 2021
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  2. Easter Bunny

    Easter Bunny Professional Engineer Platinum Member

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    You have to shim it to set the lash on the gears which is why most don't bother
     
    Easter Bunny, via a mobile device, Jan 12, 2021
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  3. jsilva

    jsilva Silver Member

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    Thanks Easter Bunny. I understand the basic concept of what it does, but I don’t understand why the lash would need to be set after it had already been set—is it something that resets when it’s removed? My main thought was that maybe it’s set to counterbalance the weight of OEM pistons/rods and replacing with non-OEM parts might necessitate it being ‘reconfigured’. But I really do know very little.
     
    jsilva, via an iPhone, Jan 12, 2021
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  4. The_big_dill

    The_big_dill Greenie Member

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    The purpose of the balance shaft is to remove subtle vibrations/imbalances.

    I re-installed it when I put my engine back together. My thinking is that since its the original balance shaft mounting to the original block surface, you won't need re-shimming. This is a risk I took as the manual indicates that you should be shimming, and the only thing I ensured was that the position of the counterweights was in the right position and there was a good amount of slack in the gears. I ran the engine with the balance shaft for about 10k km without a performance problem, but in combination with the aftermarket flywheel, rods and pistons, it created a very interesting and concerning knocking noise. It wasn't obnoxious, but I removed it to ensure that it is in-fact the balance shaft.

    I realized that the NVH from the balance shaft eliminated are barely noticeable to me, so I left it off.

    Key points:
    - I reinstalled my BS with original shimming and it worked fine.
    - The cause of the knocking I was hearing could have been due to the lack of shimming - but I had a lot of aftermarket stuff on there that could also influence this.
     
  5. jsilva

    jsilva Silver Member

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    Thanks big dill. Interesting and helpful.

    So did you do the 6 o’clock on the balance shaft and TDC on the crank?

    I was wondering if the different weighting from the aftermarket parts would affect it, and if it needs to be re-setup for the different parts.

    I’ll go ahead and leave it off.
     
    jsilva, via an iPhone, Jan 18, 2021
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  6. The_big_dill

    The_big_dill Greenie Member

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    Just follow the FSM if you want to install.

    If you leave it off, don't forget to get an BSD delete kit to block off the oil passage.
     
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  7. supertubesocks

    supertubesocks Silver Member

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    If you delete a baffle is recommended as well.
     
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