Aep Broken Trigger Not Pushing Far Enough

[gandalfthegay]

First dip into airsoft, bought an AEP just to mess around and shoot some cans. after a couple days shooting it the trigger got less and less responsive until the gun wont shoot anymore. The battery is charged and wires are connected and it does fire when I open up the gun and manually push the trigger lever further in. Ive looked at quite a few videos and forums to see if I can find a similar issue but no luck.

As far as I can tell when I pull the trigger, the little black box with the metal plate isnt pushed in enough to activate the motor and fire, so I put a shim between the little box and the lever, which resulted in only automatic fire. it looks like when the gun fire in semi automatic the level is pushed upwards by the force of the shot causing the little box the slide under and back into its default position and so a shim is not going to work.

im pretty sure im missing something, I dont see why it would be designed so every time it fires a piece of plastic would scrape against metal to reset.

also looked at a MOSFET thinking it would make the whole trigger lever useless but seems I had the wrong idea about that. any info would be greatly appreciated

dont know if you need the specific model as I think they all work the same but its a CYMA CM.127

Cheers 

[Rogerborg]

Fiddly little sods, aren't they?

 

Apologies, mine's completely stripped down at the moment into a bag of bits and there aren't a lot of decent pictures out there.

 

Sight unseen, the part I'd suspect is this:

 

 

That's the piece that the nozzle spring guide butts against.  It needs to be securely screwed down, and there's a conical spring underneath it which pushes down on rear of the the trigger bar.

 

 

 

If it's not putting enough pressure on it then the bar can jump over the top of the trigger switch on the gearbox, and in particular, the sprung piece on the left rear of the trigger bar won't be able to engage underneath the plastic semi-auto cut off lever that pops up on the left top of the gearbox, leading to full auto.

 

If that spring is missing, it'll need replaced.  If it's there, I'd try giving it a bit of a stretch, or shimming between it and the trigger bar.

 

Aside, a mosfet won't help your issues, although adding one along with a 7.4V lipo battery can really improve the semi auto response and ROF.

 

Best of luck, I know how frustrating these things can be when the tolerances are even a tiny fraction off.

 

 

 

[gandalfthegay]

Cheers, ill have a go with the spring trying to keep the lever down but im not sure if its going to help as the lever doesnt come off the trigger switch until after its fired, so the immediate problem is it firing in the first place which is because the trigger pull isnt long enough to fully push in the trigger switch. 

[Rogerborg]

Ah, I get you.  If you shim between the trigger bar and the switch, then sprung part of the bar won't come far enough forwards to engage the semi-auto cut off.

 

Well, if there's no sign of wear at the rear of the plastic trigger switch, and if you're not just shimming to replace worn away material, then I'd suspect the trigger contacts themselves.  Have you had the trigger unit open to look at the state of the contacts?  There's a tiny amount of movement in order to bridge the contacts: if there's any pitting or corrosion in there or if the contacts have splayed then I can see how it could act up.  Actually, the small amount of material and movement in here is a pretty good argument for fitting a mosfet (as I have) to reduce the current going through the trigger.

 

All 4 screws need to come out, shortest two go back in the top holes, middle length in the middle, longest in the bottom..  The trigger is held in pretty securely, it's not going to escape at this stage.

 

if there's nothing obvious at that stage, you'd be looking at taking the trigger out, cleaning the faces the contacts and the trigger metal, and possibly pinching the contacts together.  However, that trigger spring is pretty sproingy, so I'd do that with some caution.

 

Apologies for the blurry awful picture, hopefully it's clear enough what I'm pointing the finger (and arrow) at.

 

[Dusix]

Hi gandalfthegay. If problem  not in electric swich when could be in cut-off leaver, it's stuck in top position and not allowing leaver to reach switch. Another option could be bent leaver witch goes from triger, but be ceraful with it, it's  very fragile and easy breaks (tested on own experience) To check these parts you have to take apart it, a lot of video about it you can find on YouTube. Cyma cm127 internals the same like Cyma cm030.

[Rogerborg]

59 minutes ago, Dusix said:

when could be in cut-off leaver, it's stuck in top position

 

That is a candidate, as there's little spring pressure pushing it back down again. When I last had my gearbox apart, I gave a little smooth with some sandpaper then silicone lubed it.

 

However, I'm thinking the trigger contacts because of the way that it started failing by requiring more and more trigger movement, and that it's still shooting by manually pressing the trigger point on the gearbox.  Could very well be wrong though.

[Dusix]

In any way need to pull out gearbox, it's  not the easy job when you do it first time.

Rogerborg have you managed to increase FPS to 250 on AEP. I've played with this with stock parts and my max is 210 FPS. In plans to change bushings and O rings.

[Rogerborg]

No, I've got it up to 240fps using an Eagle 6 M80 spring, but I get the same fps with either the full length M80 spring, or with an M80 one that's been cut down by 3 or 4 coils to make it an easier fit.

 

That leads me to suspect that the limiting factor is the small volume of the cylinder, and the air seals at the cylinder head and the nozzle.  The nozzle in particular relies on three small o-rings to create a tight seal: the two around the nozzle itself, and the o-ring on the guide rod that seals it at the rear.  Normally I'd take them off and stretch them, but they're so thin that I suspect they might just snap, so I'd get some spares in first if you intend to try this.  Sorry, I don't know the sizes.

[Dusix]

@Rogerborg. Thanks for info. I know about leaky nozzle. When I get more free time I'll try to play whit it. A lot of info found here 

it can be useful for OP aswell.