AEG fires at random

[Hectic]

okay so i finally got my gun rebuilt the other week and took it out to a game last week it was a lil chilly so the hop up wasnt working so i didnt use it. However the other day i was going to plink with it to make sure the hop worked in warmer weather it shot okay for a while then it randomly shot without the trigger being pulled.
Then it would shoot going from safe to semi then wouldnt work with the trigger pulled but would agin going from safe to semi on its own.
Its a v2 lonex shell with a merf3.2 with a 2 signal wire setup.
When i first built it i noticed the wires became a lil pinched from the small exit hole in the back and from some pin on the top of the shell that sticks into the wire channel so i filed those bits down to avoid damage to the wires but i think there was alrdy some damage done. Is this likely a short in the wires causing this?

[Stealth]

Entirely possible and highly probable.

Tear down the gun and inspect all your wiring. Your trigger wires are probably shorting each other somewhere. Those trigger wires are also fragile as hell so you should be wrapping them in heatshrink wherever possible.

[Hectic]

I figured as much. New issue. Now WTF did i do. I opened it up to check out the wires. (they do look okay save for a few knics on the motor wires i think it may be just the sure tightness of the space to run all those wires through)
Befor i opened it it worked fine no issues with firing on its own and the 3round burst was right on time. (still no semi as some of you may alrdy know)
So to my supprise i found this work of beauty inside when i opened her up.


The shim job is sweet you can see the sector was runnin right down the middle.

The aoe should have been fine you can see where the lil tab sticks up on the sector that is about where it is set to.
You can see the last three orange teeth and its hard to see but the metal tooth is also busted off in there tho its still just barely held in by the plastic.
So WTH causes this?
Its onlly a stock echo1 spring 380-400 fps or so its lonex hs gears (16:1 i think they are) stock motor 9.6v battery so not a crazy fast build. In fact i didnt even have to change the timing from the stock setup for the 3rnd burst.
Do i just have that bad luck or suck that bad at rebuilding or what gives.

[Stealth]

If your metal tooth failed then the rest of the teeth are going to shear. Plastic is not meant to hold loads like that. Typically multi-metal tooth pistons save you in that department.

Get a new (better) piston.

What the heck is that orange thing anyway?

As a tip, the 1-wire method of wiring the MERF is preferred as it makes for less wiring to snake through. There is no performance degradation. You'll run into pinches if you do the 2-wire method, unless you clear the proper path for the wires.

[mike_sinyard]

im no gun doctor but def looks like your last tooth failed and the gear just grinded down your piston teeth. Why its shooting randomly I have no idea

[Hectic]

So one of them lonex high strength pistons (like half the teeth are metal)
Guess i change out the piston head for an aluminium one while im in there.and ima try i different cutoff lever and trigger assembly hopefully solve my semi issue too so when i put the new trigger switch ill wire it up the one wire way to avoid the random shooting lol.
Well its official i shoulda just bought the lonex complete box snd dropped it in.
Lesson learned lol.

[lurkingknight]

release tooth failure = goodbye plastic rack piston.

at least you got a chance to discover the piston issue while investigating another issue.


shs metal rack15 tooth , file down the 1st regular sized tooth and half the 2nd... get the lonex pom piston head.

[Stealth]

Originally Posted by Hectic

So one of them lonex high strength pistons (like half the teeth are metal)
Guess i change out the piston head for an aluminium one while im in there.and ima try i different cutoff lever and trigger assembly hopefully solve my semi issue too so when i put the new trigger switch ill wire it up the one wire way to avoid the random shooting lol.
Well its official i shoulda just bought the lonex complete box snd dropped it in.
Lesson learned lol.

1) SHS 15T or Lonex Red is fine.
2) Get the POM head, aluminum heads are useless, remove bearings from piston head
3) Try playing around with the trigger prongs and sled with a multi-meter and see where it "trips" the cut-off lever.

Scratch-building boxes isn't for everyone... seems easy, but tuning is crucial.

[Kos-Mos]

If you still have the electronic safety (the metal plate on the selector), it can short on the body.
That coupled with a pinched wire can make your gun shoot on it's own.

A dead MOSFET will also burn shorted (closed) and will cause the gun to enter a full-auto madness.

As for your piston, it looks like the plastic around the metal teeth bent a bit/have some play and allowed the gear to skip on the plastic tooth.

[ThunderCactus]

Looks like you need a piston with 3 metal teeth lol
And +1 to what Kos said. Only takes one bare trigger wire to cause the loop to close and the gun to shoot.

[mike_sinyard]

Originally Posted by Hectic

So one of them lonex high strength pistons (like half the teeth are metal)
Guess i change out the piston head for an aluminium one while im in there.and ima try i different cutoff lever and trigger assembly hopefully solve my semi issue too so when i put the new trigger switch ill wire it up the one wire way to avoid the random shooting lol.
Well its official i shoulda just bought the lonex complete box snd dropped it in.
Lesson learned lol.

POM for piston head
and Aluminum for cylinder head

[Hectic]

Yeah i think i actually can do it just i should have used good parts not reused the crappy echo1 parts (that orange thing is the echo1 stock piston)
Okay so ill grab the modify polycarb head remove the bearing the lonex red piston and a ka low resistance trigger setup and just run the 1 wire method to avoid the squishing of the wires. And a new cutoff lever as that is what is causing my no semi issue. If i run it by hand i can get the cutoff to disconect the trigger switch but it barely catches it and i have to push dosn on the trigger switch a lil and the cutoff lever has to be super loose.
Obviously as all you gundocs prolly know the echo1 parts work okay in an echo1 shell but fail horribly in another shell.
Thanks all for the help. This time for sure lol

[Stealth]

What? No, don't get a polycarb head.
Polycarbonate != POM
POM = Polyoxymethylene

Polycarbonate is far more brittle compared to POM, and POM is actually the material real steel M16 stocks are made of.

2 totally different things.

[mike_sinyard]

$17.00
Polyoxymethylene (POM) piston head made by Lonex with ball-bearings.

Polyoxymethylene is a low-wearing, low-friction, high-strength and lightweight plastic. Its properties make it an excellent material for a piston head. Other manufacturers use polycarbonate, which is also lightweight and high-strength, but is extremely brittle and will shatter leading to catastrophic failures.

[ThunderCactus]

It's also super fun to machine and makes a wicked mess