KA M4 re-assemble

[slowbird]

I'm having problems with my new KA M4A1 and after opening it all up and not seeing what's wrong with it, I figured I'd reassemble it before taking it to my Gun Doc. (cause I don't want to give him a box full of parts)

Anyways, I'm trying to get the gearbox back into the lower and it seems to be fouling on the selector switch assembly...and the odd time I do get it in there the selector switch becomes too tight.

Is there a trick to getting it all lined up in there?

[K3vX]

Gun docs are normally used to receive a failed dissasembly in zip-loc bags.

I don't know much about M4s, but I'd say compare with reassembly video and try to find the source of the binding.

[slowbird]

Whether they are used to it or not, I'd rather take the time to put most of it back together. Less loose parts.

I've looked at many videos but none really explain it too well.

Even when attaching the barrel/upper most videos fail to explain lining up the hop up and nozzle properly to get it all to fit.

It's those little tips I'm looking for. To get that gearbox into the lower without binding the selector switch.

[Stealth]

The screws securing the grip to the mechbox may be too tight.

The switch should be in semi or auto to make aligning the selector plate easier.

[slowbird]

Originally Posted by Stealth

The screws securing the grip to the mechbox may be too tight.

The switch should be in semi or auto to make aligning the selector plate easier.

Thanks for the reply, but this was before the grip was attached. I couldn't get the Mechbox into the lower.
I did get it in there. I think the Mechbox shells weren't closed tight enough together.

I think I also fixed my original issue which was a loose motor wire.

[Styrak]

Originally Posted by slowbird

I think the Mechbox shells weren't closed tight enough together.

That's a strange issue. Mechbox screws should never be loose, always tighten them down solid.

[slowbird]

Yeah, I'll be the first one to admit I had no idea what I was doing, but I bought this gun to learn on so I dove in head first.

I think something was stopping the 2 shells of the mechbox from completely sealing together. Something inside wasn't in properly. (my guess is the anti-reversal latch)

After re-opening it all, swapping the spring, and making sure all was assembled properly it plopped in just fine.

Gun works fine now and shoots at a more reasonable 400ish fps.

[KenTsui]

It's going to be hard to help you with this without actually having it in our hands. Perhaps a video of you attempting it may help?

Even then, I would just be patient and keep trying until you figure out what's stopping the MB from going in. At this point, there must be something physically blocking it, right? You just got to be patient and try and spot it out.

I've never really had problems inserting a MB into the gearbox, except when:
- I installed thicker wires into a small body / not using default wire routing
- I forgot the bolt catch was there (SCAR)
- I installed something in the wrong order (something outside of the MB that was supposed to be installed after it's been inserted into the lower)

That's all I can think of right now...

[akira69]

I've sometimes had the cylinder not sitting quite right cause me me a similar issue

[venture]

Anybody ever have this problem with the KA M4's:

When I reassemble the gearboxes in them, a small percentage have the piston come out of its track upon closing. When you test the box, the symptoms are gears turn fine and nozzle moves fine, but piston does not engage. When I encounter one of these gearboxes I sometimes have to take apart and reassemble the box several times before the piston will stay where it belongs.

Yesterday I encountered one (jogged my memory of past occurrences; hence this post) and after trying to assemble the gb 4 times, I chucked the piston and put an SHS one in. It closed up first time successfully.

Other ones that I have encountered in the past have led me to change pistons and the same thing happened until I changed to another piston. Some of those had me assembling the gearbox up to 7 or 8 times.

My question for the experienced gun docs is: If you also have encountered this, did you figure out a way to get the gb together? It is very frustrating when a 45 minute job turns into an all day affair.

[ccyg8774]

Originally Posted by venture

Anybody ever have this problem with the KA M4's:

When I reassemble the gearboxes in them, a small percentage have the piston come out of its track upon closing.

I had a similar issue once, but I was using a ported cylinder so I was able to see if the piston is in the right position while I close the GB.
It came out of the track once and I was able to push it back with a small allen key, through the port on the cylinder before fully closed the GB.

[slowbird]

Originally Posted by KenTsui

It's going to be hard to help you with this without actually having it in our hands. Perhaps a video of you attempting it may help?

Thank you very much. I very much apreciate your help. I have solved all my problems and have listed what I think was the cause of those problems.

I think the issue with the Mechbox not fitting in the lower was due to the Mechbox halves not being pressed securley together.
My original issue with the gun not firing I think was due to a very loose motor wire.

Originally Posted by venture

Anybody ever have this problem with the KA M4's:

When I reassemble the gearboxes in them, a small percentage have the piston come out of its track upon closing. When you test the box, the symptoms are gears turn fine and nozzle moves fine, but piston does not engage. When I encounter one of these gearboxes I sometimes have to take apart and reassemble the box several times before the piston will stay where it belongs.

Yes! I had this issue when I was trying to get it all back together. Motor was spinning fine but not moving the piston back against the spring.

I opened the Mechbox again. Made sure everything looked ok. Reassembled and tried again and it worked.

very odd.