King Arms M4 - Selector switch problem

justynmagz · November 9th, 2012, 01:02

Hello all,

First off I've been AV'ed (1 week ago) and I tried posting this in the Gun Doctor > AEG Solutions section but it seems I don't have access for some odd reason...

So I bought the KA M4 a couple weeks ago. Haven't fired anything from it yet but wanted to upgrade a couple things.

I took apart the rifle and changed out the spring, which was fine, and also re-wired it to the rear to allow my new crane stock. The problem is however that when I was reassembling the rifle back together, when I get the gearbox into the lower and move the selector switch from safe to semi and to auto it seems to be quite hard to switch.

I've taken it apart multiple times to try and assess a different problem inside the gearbox and also read other reviews online, but it still seems to be sometimes normal to go from safe to semi and always really tough to go from semi to full.

Looking at the functionality of it, it looks as if its having a tough time switching because when moving the red selector plate (attached to the gearbox) into auto it seems to catch on the shim backing (sorry don't know the name of this piece).

Anyone have any ideas how to fix this? It would be much appreciated.

Styrak · November 9th, 2012, 03:39

Strange as this sounds, it could be as simple as the order you're putting the gun back together. Both the grip and the buffer tube pull on the mechbox, possibly taking it out of good alignment when you tighten it down before you put the other part on. The other wildcard is the mechbox crosspin.

BennyBoy · November 9th, 2012, 03:53

When you rewired it, one of the wires heading pass the trigger is getting in the way of the mechanism that puts the trigger on safe. Just press it back and maybe glue it down.

What happened to me the other night....smooth sailing after I moved the wire out of the way.

venture · November 9th, 2012, 08:06

You don't post in solutions. Just the doctor forum. Admins move stuff to solutions when good solutions are found.

justynmagz · November 9th, 2012, 10:46

BennyBoy - Will give this a try and get back with an answer...

Venture - very good call....fail on my part...:P

justynmagz · November 9th, 2012, 12:47

So I took a look at the wire and it doesn't appear its hitting the level that puts it in safe...see pictures below...

The circled area is what I believe is whats hitting the selector switch and causing resistance.

Thoughts?

Andre_1999 · November 9th, 2012, 16:28

Maybe just file down the back of the selector plate?

coach · November 9th, 2012, 16:49

Did you change selector plates or upgrade to bearings?

The selector plate should be slotted to allow space for the bearing. You should not need to file the back of it to accommodate the rubbing. Nor would I do that mod. Selector plates can be pretty fragile and are prone to breaking.

Something else is the cause.

Does your mechanical safety move smoothly? The black thing on the lower left of your second picture. If you rotate that so it doesn't interfere with the selector plate, can you slide the selector plate back and forth with ease or is it binding there?

justynmagz · November 9th, 2012, 18:17

Yes the mechanical safety moves fine as does the selector plate. The issue really just seems to be that the selector switch backing is rubbing on the bearing.

Scrivah · November 9th, 2012, 22:34

I have the same AEG. My first thought too was the wiring, but you seemed to diagnose that was not the issue. You have a picture with the bearing circled and the mechbox apart. It could be like you said rubbing on the bearing but also look at the bearing when the box is fully assembled with the gears inside. At times the gear pin that runs thru the middle of the bearing actually sticks out further than the bearing does and it should be at least flush or a fraction bit recessed in the middle of the bearing A quick file down or dremel to shave is down may be all you need to do.

justynmagz · November 14th, 2012, 00:34

So I tried what's been mentioned above (aside from filing down the bearing) and tried pushing the bearing in slightly to see if that would make a difference. It made a small difference and doesn't rub as much.

Will keep disassembling and reassembling to see if I get lucky and will keep you all posted.

Thanks for the help everyone!

BennyBoy · November 14th, 2012, 00:38

have you tried not tightening the screw too tight? my ares m4 is hard to change selector when it's too tight but it's awfully lose if I don't....had to thread lock it on

Scrivah · November 15th, 2012, 06:09

Any luck? My buddy and I had this problem when we put his KA m4 back together last night. It was normal going from safe to semi and then was tough going from semi to full auto. The problem occured when he tightened down the screws that hold the grip to the gearbox. Try to move the selector without the grip screwed on and see if it moves freely. If that works its a matter of alignment.

mike_sinyard · November 15th, 2012, 08:48

Plus whn i had the grip off, i pulled up on the gesr box and moved it around a little bit. When the grip is off the selector switch should move freely. When its on it gets stuck. So take the grip off and pull on the gearbox and at the same time try moving the selector switch. If its tough then its a matter of wiggling the gearbox and pulling on it so it seats properly. I was just pulling on the gearbox and wiggling it theough the pistol grip and moving the selector switch when i noticed it just started working again. Let me know how it goes

justynmagz · November 19th, 2012, 13:18

So I found the problem to all of this! The culprit was the anti-reversal latch!

Since I was a new to opening the gearbox, I pulled up a video on youtube on its disassembly. I followed the video and when it came time to re-assembly I was pretty ok with putting it back together. There weren't many reassembly videos from open gearbox to closed gearbox that I remember where they explained how to fix this.

The problem was that when reassembling the gears, when I was putting the anti-reversal latch back in I wasn't compressing the spring to ensure it was past 45 degrees, rather it was sitting more at 20 degress, thus not even sitting properly within the gearbox. This was also causing a gearbox seizure even in semi.

I corrected this, and the first time putting it back together it went in fine with NO resistance on the selector switch.

I now have a working M4.

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November 9th, 2012, 01:02	#1
justynmagz Trader rating Join Date: Jan 2012	King Arms M4 - Selector switch problem Hello all, First off I've been AV'ed (1 week ago) and I tried posting this in the Gun Doctor > AEG Solutions section but it seems I don't have access for some odd reason... So I bought the KA M4 a couple weeks ago. Haven't fired anything from it yet but wanted to upgrade a couple things. I took apart the rifle and changed out the spring, which was fine, and also re-wired it to the rear to allow my new crane stock. The problem is however that when I was reassembling the rifle back together, when I get the gearbox into the lower and move the selector switch from safe to semi and to auto it seems to be quite hard to switch. I've taken it apart multiple times to try and assess a different problem inside the gearbox and also read other reviews online, but it still seems to be sometimes normal to go from safe to semi and always really tough to go from semi to full. Looking at the functionality of it, it looks as if its having a tough time switching because when moving the red selector plate (attached to the gearbox) into auto it seems to catch on the shim backing (sorry don't know the name of this piece). Anyone have any ideas how to fix this? It would be much appreciated. __________________

November 9th, 2012, 03:39	#2
Styrak Trader rating Join Date: Jan 2007 Location: Saskatoon, SK	Strange as this sounds, it could be as simple as the order you're putting the gun back together. Both the grip and the buffer tube pull on the mechbox, possibly taking it out of good alignment when you tighten it down before you put the other part on. The other wildcard is the mechbox crosspin. __________________ Airsoft Sales and Repair/Upgrade Services

November 9th, 2012, 08:06	#4
venture Trader rating Join Date: Jun 2005 Location: Halifax	You don't post in solutions. Just the doctor forum. Admins move stuff to solutions when good solutions are found. __________________ Visit us at :www.ventureairsoft.ca

November 9th, 2012, 10:46	#5
justynmagz Trader rating Join Date: Jan 2012	BennyBoy - Will give this a try and get back with an answer... Venture - very good call....fail on my part...:P __________________

November 9th, 2012, 12:47	#6
justynmagz Trader rating Join Date: Jan 2012	So I took a look at the wire and it doesn't appear its hitting the level that puts it in safe...see pictures below... The circled area is what I believe is whats hitting the selector switch and causing resistance. Thoughts? __________________

November 9th, 2012, 16:28	#7
Andre_1999 Trader rating Join Date: Jun 2012 Location: Brampton, Ontario	Maybe just file down the back of the selector plate?

November 9th, 2012, 16:49	#8
coach aka coachster Trader rating Join Date: Mar 2008 Location: T dot	Did you change selector plates or upgrade to bearings? The selector plate should be slotted to allow space for the bearing. You should not need to file the back of it to accommodate the rubbing. Nor would I do that mod. Selector plates can be pretty fragile and are prone to breaking. Something else is the cause. Does your mechanical safety move smoothly? The black thing on the lower left of your second picture. If you rotate that so it doesn't interfere with the selector plate, can you slide the selector plate back and forth with ease or is it binding there? Last edited by coach; November 9th, 2012 at 16:54..

November 9th, 2012, 18:17	#9
justynmagz Trader rating Join Date: Jan 2012	Yes the mechanical safety moves fine as does the selector plate. The issue really just seems to be that the selector switch backing is rubbing on the bearing. __________________

November 9th, 2012, 22:34	#10
Scrivah Trader rating Join Date: Oct 2012 Location: London, ON	I have the same AEG. My first thought too was the wiring, but you seemed to diagnose that was not the issue. You have a picture with the bearing circled and the mechbox apart. It could be like you said rubbing on the bearing but also look at the bearing when the box is fully assembled with the gears inside. At times the gear pin that runs thru the middle of the bearing actually sticks out further than the bearing does and it should be at least flush or a fraction bit recessed in the middle of the bearing A quick file down or dremel to shave is down may be all you need to do.

November 14th, 2012, 00:34	#11
justynmagz Trader rating Join Date: Jan 2012	So I tried what's been mentioned above (aside from filing down the bearing) and tried pushing the bearing in slightly to see if that would make a difference. It made a small difference and doesn't rub as much. Will keep disassembling and reassembling to see if I get lucky and will keep you all posted. Thanks for the help everyone! __________________

November 15th, 2012, 06:09	#13
Scrivah Trader rating Join Date: Oct 2012 Location: London, ON	Any luck? My buddy and I had this problem when we put his KA m4 back together last night. It was normal going from safe to semi and then was tough going from semi to full auto. The problem occured when he tightened down the screws that hold the grip to the gearbox. Try to move the selector without the grip screwed on and see if it moves freely. If that works its a matter of alignment.

November 15th, 2012, 08:48	#14
mike_sinyard derp! Trader rating Join Date: Nov 2012 Location: London, ontario	Plus whn i had the grip off, i pulled up on the gesr box and moved it around a little bit. When the grip is off the selector switch should move freely. When its on it gets stuck. So take the grip off and pull on the gearbox and at the same time try moving the selector switch. If its tough then its a matter of wiggling the gearbox and pulling on it so it seats properly. I was just pulling on the gearbox and wiggling it theough the pistol grip and moving the selector switch when i noticed it just started working again. Let me know how it goes __________________ ALPHA Bang one, Bang em' all!

November 19th, 2012, 13:18	#15
justynmagz Trader rating Join Date: Jan 2012	So I found the problem to all of this! The culprit was the anti-reversal latch! Since I was a new to opening the gearbox, I pulled up a video on youtube on its disassembly. I followed the video and when it came time to re-assembly I was pretty ok with putting it back together. There weren't many reassembly videos from open gearbox to closed gearbox that I remember where they explained how to fix this. The problem was that when reassembling the gears, when I was putting the anti-reversal latch back in I wasn't compressing the spring to ensure it was past 45 degrees, rather it was sitting more at 20 degress, thus not even sitting properly within the gearbox. This was also causing a gearbox seizure even in semi. I corrected this, and the first time putting it back together it went in fine with NO resistance on the selector switch. I now have a working M4. __________________

King Arms M4 - Selector switch problem

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