Chronic GB lock-up, how to fix?

Discussion in 'Gun Building, Modifications & Repairs' started by Mighty_Mouse, Dec 2, 2012.

  1. Mighty_Mouse

    Mighty_Mouse New Member

    270
    0
    Cookeville
    Hello all,

    I keep getting a gun sent to me because the gearbox is seizing up. Every time I take the gun down (Echo 1 G36, stock) and pull down the AR latch, the gear box unlocks, I test fire it and it seems fine.

    When ever I send it back to the owner, he uses it for less than 20 minutes before it seizes up again. Obviously this is pretty frustrating for both of us.

    So I've got two questions:

    1) Could this be a voltage/current issue? I'm testing the gun on a 9.6v 2200mah battery and it is working fine. The owner has the stock 8.4v battery and it locks up. Or is this just coincidence?

    2) If it's not a voltage issue, what is it?
     
  2. Lefse

    Lefse Well-Known Member Supporting Member

    4,751
    165
    If it locks up with the stock battery and not the one you're testing it with, then that points toward his battery being underpowered. You say he uses it for 20 minutes before it locks up, Does this mean that it works normally, but locks up after a while with the stock battery? Does the owner have any idea at all how batteries work?
     

  3. stat226

    stat226 New Member

    282
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    Limerick
    Also does the owner have a smart charger? If not, then he probably just needs a new battery and a smart charger to avoid future issues.
     
  4. TYSONtheSNIPER

    TYSONtheSNIPER New Member

    1,939
    3
    Edmonton
    It sounds like weak batteries as pointed out by everyone else. But maybe the shim job is also potentially causing some problems (shims are tight). Has the gun been re-shimmed at all?
     
  5. Mighty_Mouse

    Mighty_Mouse New Member

    270
    0
    Cookeville
    That I do not know. This gun was bought second-hand, I don't think the current owner asked very many questions.

    I think the gun now has a stripped piston, but it will be a few days before I have time to open the gearbox to verify this.
     
  6. TYSONtheSNIPER

    TYSONtheSNIPER New Member

    1,939
    3
    Edmonton
    Well, when you get to cracking it open it wouldn't hurt to check the shims, and if you choose to, you may as well fix them. At least that way you can cancel that out of the possible list of things that might be causing this lockup.
     
  7. Mighty_Mouse

    Mighty_Mouse New Member

    270
    0
    Cookeville
    I'll have to see how much the owner wants to spend. He is paying me for my time.

    If it were my gun, I'd redo the shimming, greasing, and wiring by default. But the owner/customer may only want to pay me to put the piston in and nothing else.
     
  8. TYSONtheSNIPER

    TYSONtheSNIPER New Member

    1,939
    3
    Edmonton
    That's true, let him know that could be an issue though. Maybe that will persuade him enough.
     
  9. Mighty_Mouse

    Mighty_Mouse New Member

    270
    0
    Cookeville
    This is still frustrating me.

    The owner is now using a battery identical to mine (idk if he uses a smart charger though)

    I have now re-shimmed the gun, and although I had to shim the poo out of the sector gear, I don't think the shimming is too tight. I can tell you it certainly wasn't too tight before, as things were just kinda free floating around. I've never had this problem with the guns I've reshimmed before, so I think I know how to shim well enough.

    Does anyone have any suggestions on how to take care of this?
     
  10. TYSONtheSNIPER

    TYSONtheSNIPER New Member

    1,939
    3
    Edmonton
    Ask the owner if he continuously uses the gun on full auto. And if he shoots on full auto in bursts or if he just holds the trigger down continuously.

    That's the only thing I can think of that may still be causing this gear box lockup. Especially now that he's using the same battery you use to test it.
     
  11. 701st_Paul

    701st_Paul New Member

    3
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    NYC
    Check the anti-reversal latch and bevel gear. see if the latch has uneven wear...
     
  12. S1kkguy

    S1kkguy New Member

    489
    2
    London
    If all seems well in the gearbox, then it may be the motor? You say that it was second hand and all is stock. Worth a check with a different motor.
     
  13. 701st_Paul

    701st_Paul New Member

    3
    0
    NYC
    ^ 2nd... Forgot to mention as well.