AK firing at all times

Discussion in 'Gun Building, Modifications & Repairs' started by TheSovietSniper, Nov 8, 2015.

  1. TheSovietSniper

    TheSovietSniper New Member

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    Kelso
    Hey, all. My first post on this site, so please go easy on me :D


    Anyway, I recently ordered a CYMA CM040c (An AK-74M in all respects) and I just fired it for the first time yesterday.

    It worked great, was very powerful, and was accurate. However, it then started firing on it's own until I disconnected the battery. After a bit of tinkering, I found it does this regardless of what the selector switch is set to (Safe/Full/Semi). My team leader said to take off the pistol grip and access the motor, and make sure the wires aren't bare or touching anything. Everything looks okay to me.


    Does anyone have a fix for this, or even a theory as to what could be happening? Thanks.
     
  2. Tortoise

    Tortoise Active Member

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    There's a short somewhere. Check all the wiring to make sure that it's intact and nothing is shredded. You'll want to remove the gearbox to get a good look at all the wiring (AK gearboxes are easy to remove), and possibly open it up if you have the experience.
     

  3. TheSovietSniper

    TheSovietSniper New Member

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    Kelso
    I've never taken one apart, I'll have to look up a video on that. The gun is brand new, should I be worried that this is happening?
     
  4. Tortoise

    Tortoise Active Member

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    It's not really a common thing with new guns (especially AK's, the wires aren't usually crammed into anywhere) but when the gun is firing by itself without pulling the trigger, it means that the circuit is being closed somewhere, and most likely not at the trigger contacts (the shuttle could be stuck in them for whatever reason but I've never heard of that happening before). Just inspect along the entire wire system, starting at the battery, for anything unusual.

    Be careful taking your gun apart for the first time also, there's a few little pieces you don't want to misplace. AK's are pretty good about that though.
     
  5. TheSovietSniper

    TheSovietSniper New Member

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    Kelso
    Several airsofters told me that this happened because I don't have a MOSFET, and one said that it is "Definitely due to your trigger trolley fusing together from arcing" and that I need to get a part of Evike.

    Only problem with that is the part has a bad review, is the only one of its kind on Evike, and the other (similar) part has likewise bad reviews and that one doesn't have a MOSFET.


    Is it a safer bet to just send the thing back?
     
  6. mikejosephman

    mikejosephman Moderator Alligator Staff Member Moderator

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    It definitely doesn't need a mosfet. I'll assume you are using the stock battery, which isn't causing the problem.

    Your trigger contacts are the problem, and if it's more practical for you to send it back, go right ahead. In my experience, it's cheaper just to diagnose and fix yourself, or have someone look at it and fix.
     
  7. theonlyBuster

    theonlyBuster Active Member Lifetime Supporter

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    S. Florida
    Correct TheSovietSniper, the problem is most likely your trigger contacts. It sounds like they're stuck/sticking. A few things can cause this. If the gun is fairly new, the contacts are probably too close/tight, preventing them from releasing when the trigger is released. If this is the problem, you're going to need to go into the gearbox and simple pry them apart a bit OR you can replace them all together. New trigger contacts are pretty cheap.
    IF the gun is still under warranty via store or manufacture, consider contacting them FIRST before going into the gearbox.

    If the gun has had some field use with a Lipo or other high output battery, you likely have carbon build-up on the contacts causing them to stick. It's fairly normal, and you'd NEED to replace the contacts. While you're replacing, if you plan on continuing to use the battery, you should also consider installing a MOSFET. The MOSFET will help regulate the current minimizing the carbon build-up on the contacts. Now you will still get carbon build-up, BUT it will be dramatically slower than it would be if you didn't have the MOSFET.

    But BEFORE you go into the gearbox, confirm whether or not the gun is still under warranty AND confirm any hidden fees you may have to front in order to go through the warranty/RMA process. Most stores require you pay shipping there and often back, a few don't.

    A trigger assembly will run you less than $10 shipped to your door. Plus wiring and connectors (if desired) is a couple more bucks. And a Mosfet can run you anywhere from $10 to $100 depending on the brand and functions. Plus the tech's fee to install, if you cannot do this yourself. You're looking at about $60 + MOSFET for a tech, and maybe $20 + MOSFET if you did it yourself.

    IF you have a tech do it, you might as well toss in a few bucks for a shim and lube job for increased longevity since he's already in the gearbox.

    Side note: It likely isn't a short. If it were, when the trigger is released, the gun should stop shooting as the connection has been broken.

    -mobile device-
     
  8. TheSovietSniper

    TheSovietSniper New Member

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    Kelso
    Thank you for the detailed response. I figure I should get that sucker open and pry at the contacts, then. You said they may be too close, can I move them a bit further away, or will the problem alleviate itself when I pry them apart?

    Also I dunno about the shipping part, I really did want to do this for as low of a cost as possible. I also have zero knowledge of gun maintenance other than giving the insides a lookover once in a while to make sure nothing is out of place, so I guess now is as good a time as any to jump into the field of fixing my gear on my own.

    Also the battery isn't stock, but it isn't a LiPo. It is a Matrix GenStar High Output 8.4V 1600mAh NiMH Stick Type Battery (Title taken from Evike), could this be the issue?
     
  9. theonlyBuster

    theonlyBuster Active Member Lifetime Supporter

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    Working in the gearbox honestly isn't that complicated. Intimidating to someone new, yes. But after a few, you get pretty confident and fairly comfortable working in them. There are TONS of disassembly videos online for the V3 gearbox, I doubt you'll have any trouble finding a helpful video to follow along with.

    Just know one thing. The second you open the gearbox, consider your warranty completely null and void, period, end of discussion, don't even attempt to argue with the store/manufacture.

    The trigger contacts is a simple system. Honestly just by looking at it, you can basically figure out what's needed. Pry the 2 metal contacts on the left a bit further apart, but not so far as to that they connect make contact with the single contact on the right.
    Also, TOTALLY forgot about this, ensure the "release" spring is in place. You can see it on the table next to the trigger contacts. This is what pulls the contacts apart after you release the trigger. This can fall out of place. If necessary, you can faction another spring by removing the spring from a click-pen and fashioning it to fit into place with your contacts.
    [​IMG]

    -mobile device-
     
  10. TheSovietSniper

    TheSovietSniper New Member

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    Kelso

    The pen spring thing... Sounds genius! I talked to Evike; they said submit an RMA form. If that doesn't go through for whatever reason, then I will indeed see about what you said.

    Now, by "Fashioning" the spring, what do you mean? Do I use some adhesive to make it stay?

    UPDATE: I figured screw it, found videos on how to take apart the gearbox. After some tinkering, obscenities because the gearbox wouldn't come apart, some serious contemplating of "How the hell did I not see that screw holding it together?!", and some brute strength, I got it open. I went straight for where the trigger contacts are, and sure enough, a little broken piece of metal that very well could have been a spring was there. I removed it.


    Now, I have no idea how to put this together. Will get a buddy to help me on that one. Anyway, should there be anything between the two copper trigger contacts, or will they touch when I pull the trigger? I'd hate to put it back together and then for it not to work because I don't have a little spring to put in between them/forgot to put it in.
     
    Last edited by a moderator: Nov 10, 2015
  11. Jeranhound

    Jeranhound Active Member

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  12. TheSovietSniper

    TheSovietSniper New Member

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    Kelso
    The piece of metal/spring kind of looked like this: AK spring.JPG



    It was lodged in between the trigger contacts. Is that part 100% necessary or can I leave it out? I don't know where it's supposed to go back to.
     
  13. DreadCo526

    DreadCo526 New Member

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    Sylvester
    That is your AR-latch spring and yes it is 100% necessary, why would they even bother putting it in if it wasn't?

    Do you know where it goes?

    Oh and take a picture of the actual spring you took out.
     
  14. TheSovietSniper

    TheSovietSniper New Member

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    Kelso
    Not sure where it is supposed to be, I just found it lodged between the two trigger contacts thus completing the circuit and that's what was making it fire all the time. And pic incoming.

    My bad, this was it. I took the gearbox apart late at night, the thing found between the trigger contacts looked like this: Problem.jpg
     
    Last edited by a moderator: Nov 10, 2015