Cybergun m249 featherweight.

Discussion in 'Gun Building, Modifications & Repairs' started by The Lords Hand, Jul 29, 2021.

  1. The Lords Hand

    The Lords Hand Member

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    So far added new rocket high torque 16tpa motor. Prommy red bucking and nub. Bipod, scope, scope protector for externals. Took it too my first game. Using a 7.2 3000mah nimh battery to try to keep rate of fire lower. Gears started grinding and locked up. Screeched a few times so I stopped using. Opened it up and piston was stuck back. Not sure if that means anything. Looks to be metal shavings in gearbox. Gear teeth look shiny on ends at the edges. Going to clean out the shavings and put back together and see if it works. Pretty sure I tried shooting through a jam. Never had any of my guns jam before so wasn't sure what was happening. Bb was stuck in hop up. Opened up and gears moved fine while open. So did the piston get locked back somehow while trying to shoot? I'm not sure.
     

    Attached Files:

  2. ma_airsoft

    ma_airsoft Well-Known Member Supporting Member

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    need to shim the gearset to the motor
     

  3. The Lords Hand

    The Lords Hand Member

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    Like the motors too low?
     
  4. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Never shoot through a jam.

    In fact the exact opposite. Due many low quality AEG's out there you will break nozzles and/or tappet plates trying to shoot through a jam. Rather with the low end models, get off the trigger as quickly as possible.
     
  5. The Lords Hand

    The Lords Hand Member

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    I know. I just mentioned that that is what I think happened. Not that I tried to intentionally shoot through a jam.
     
  6. ma_airsoft

    ma_airsoft Well-Known Member Supporting Member

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    judging by the wear im gonna say yes but that might just be the angle of the photo
     
  7. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Well those are low market "element" style gears. They could have been self-lapping themselves into an operating manner.

    I would say this is one of the few AEG's that one should open up even when new to check the factories work and do the basics to get it working right. One didn't need to do that any more since 2009 with most other factories.
     
  8. The Lords Hand

    The Lords Hand Member

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    I still know next to nothing about what im looking at. Other than what the parts are. This will be my main gun so i want to put more durable parts in. Especially since there isnt a direct gearbox i can replace it with.
     
  9. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Quite honestly...change "nothing" until a part breaks.

    You can make it run more smoothly, but nothing on the market is really an "upgrade" for you right now, unless you want to do a lot of hand fitting and paying the price of your AEG in a few handful of parts.

    Those metal shavings on reflection is most likely generated between bevel and pinion.
     
  10. The Lords Hand

    The Lords Hand Member

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    And fixed. Firing like normal. So what mechanically probably happened? Gun jammed. Gears sounded grindy. Then just a loud screaching with no grinding. Also is a 7.2v 3000mah nimh ok to use with this sind the voltafe will drop at some point? Or should i only use the 8.4v 3800mah nimh? I have a 9.6 but id rather it shoot slower to use less ammo and prolong its life. And with the motor also im guessing i should use the 8.4v.
    https://www.evike.com/products/12507/

    The piston doesnt need upgrading? Padding/padded?
     
  11. The Lords Hand

    The Lords Hand Member

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    Next up trying to get the muzzle break off without breaking it so i can attach the sound amplifier.
     
  12. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Use the old adage. If it's not broken...don't fix it.
     
  13. Ben3721

    Ben3721 Well-Known Member

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    I would check to make sure the piston didn't get stuck back on on the guide bearings first.

    But yeah sounds like pme. It's really hard on the gears when has to catch a flying piston like that. Plastic pistons get damaged instantly, metal rack ones can tolerate it a bit more. But if you cycle it 20 or more times, then you likely caused damage. Those hard steel metal shavings will work through your cylinder, wrecking the o ring of the piston head and then scratch the barrel. When metal dust or shavings are thrown around you have to clean the entire gearbox out.

    It sounds like the motor height was off or bevel height was too high caused the pinion to forcefully spin for a moment too, a jam can cause that if the aren't shimmed properly, a aeg can still run if the bevel and pinion are barely touchy, it just won't sound right and can slip.
     
  14. The Lords Hand

    The Lords Hand Member

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    Yeah its working now. I think the motor was too low. Well see how it holds up next game.
     
  15. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    I don't think it's PME...his voltage is not very high, his motor is not high speed nor does he have a hs gear set.
     
  16. The Lords Hand

    The Lords Hand Member

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    New question. What motor would be good for lots of FA fire and run cool. I read the posts about motors but the information is beyond me at this point. Guns stock as far as parts that pertain to this. Ill be using a 8.4v 3800mah battery. I'm not concerned about a high rate of fire. I'm concerned about alot of firing and not overheating the motor. I know it's a v2 and its not intended to be played like a m249 gearbox. But I'm also sure I'll play it harder then I should.
     
  17. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Any motor is not going to run hot at 8.4V. Well, any well made motor won't do that...SystemA and Devil Jets will run hot due to design inefficiencies...
     
  18. RWS3

    RWS3 New Member

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    use a 9.6 battery. i use 11.1s but i doubt it will hold up forever.
     
  19. wetpee

    wetpee Active Member

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    but if it jammed and the trigger continued to be pressed, it could PME.

    @OP its hard to tell from the photo, but it looks like the inner section of angled teeth on the bevel gear (meets with the motor pinion) is roughed up, whereas the outer section looks smooth, indicating the motor would have been too high. In any case, you really can't just throw a new motor in and expect it run fine. You should be re-shimming the gears to match the dimensions of the motor and its pinion gear because every motor and every pinion are going to be a little different and factory shimming is usually not that great on most replicas. Some motors are legitimately too tall and custom modifications have to be made to run them smoothly. It looks like there is brush material or something that would have come from the inside of the motor in that deposit of debris which would indicate excessive load on the motor or the motor is poorly made and something is rubbing on the inside that shouldn't be.
    When the motor is too low, worst case is uneven wear. When the motor is too high, worst case is essentially exactly as you described. Pinion bites on the bevel gear and can cause the system to seize.
    If you're not yet ready to get into shimming and doing real AEG work and maintenance, just bringing the motor height down some could be fine for a bit. Ideal position is to have the pinion as low as possible while still maintaining 100% or as close to 100% tooth contact as possible. The one problem now is that the bevel is clearly damaged so it will never run as intended again. You can attempt to correct the damage with a file and some sandpaper. If you use a bevel gear from a different manufacturer, it is highly advisable for you to reshim the whole gearset. I'm not sure who makes the gears for your model. Look up some videos on AEG shimming.
     
    Last edited: Nov 25, 2021 at 2:11 PM