This has me baffled...need help

[ronin49v]

upgrading a TM mechbox, because it would stop shooting after a few shots.

Got new:
-Trigger assembly (classic army front wired) I thought this was the problem
-systema cylinder head and nozzle
-silent piston head ( element extra part )
-new G&P gears swapped with A&E generic gears ( the gearbox didn't work with these either.)
- New 6mm bearing bushings
- external fire selector plate
- bearing spring guide

Stock:
-Cylinder
-Piston
-reverse gear
-tappet plate

I've opened and re-shimmed this @#%^ gearbox at least 8 times now with the same result. shoots a few times and then stops working like the gears are jammed.
I checked the shimming over and over and doesn't seem to be the problem.
the trigger assembly is new and I tested the connections work with a motor before closing the gearbox and works perfectly everytime i pull the trigger.
It stops working after I put motor in handle and fire it a couple of times. DAMN driving me crazy, any ideas anyone? Help?

The only thing I haven't replaced is the tappet plate and I'm not sure if its stock, looks kinda flexible to me but hey I didn't have an extra one to swap and test.

any experts out there, any suggestions will be welcome. I've opened lots of gearboxes and re-shimmed upgraded before with no problems, this one's got me totally stumped

stumped and pissed
roger

[Cheesevillage]

My gun had this issue -- Styrak fixed it after much irritation -- he shaved the trigger ever so slightly as I remember. Maybe he'll chime in...

I guess the question is whether or not the motor is actually engaging (as you say it is) and something is binding (as opposed to trigger issues).

[Styrak]

As Cheesevillage was saying, I've fixed this before...

The reason it stops when you fire a few times is that the trigger switch slips off the actual trigger, and when the trigger resets back to normal position, it can't pick up the trigger switch again. I shave a little off the depth off the front of the trigger where it engages the trigger switch so that it picks up the trigger switch normally.

[Kos-Mos]

When you say it works a few shots, do you mean the rifle fires correctly 2-3 shots?

Have you double checked that your battery is full and tested with a known good battery too?

[venture]

Next time you have it apart check the little block cast into the left side of the gearbox. I had this trouble twice now. First time I did like you - had the gb apart 8-10 times, put 3 brand new trigger mechs and 2 brand new steel triggers in. Then I found the problem: Right in front of the cutoff lever and right behind the trigger block is a small square piece in the casting of the gearbox. If this snaps off, then your trigger block slips from the trigger every couple of shots and you cannot get it back right until you take the gb apart again.

I can't find a good picture of it, but look .5 cm directly forward of the hole where the cutoff lever screws on:

[audi_bhoy]

Originally Posted by venture

Next time you have it apart check the little block cast into the left side of the gearbox. I had this trouble twice now. First time I did like you - had the gb apart 8-10 times, put 3 brand new trigger mechs and 2 brand new steel triggers in. Then I found the problem: Right in front of the cutoff lever and right behind the trigger block is a small square piece in the casting of the gearbox. If this snaps off, then your trigger block slips from the trigger every couple of shots and you cannot get it back right until you take the gb apart again.

I can't find a good picture of it, but look .5 cm directly forward of the hole where the cutoff lever screws on:

I agree with him, happened on my Systema reinforced gearbox, I drilled a hole where the square block was sitting before snapping off, and I then inserted a nail press fit, cutted to right lenght, shaved on selector plate side so it doesn't scratches, and it works awesome.

[ronin49v]

ok, the I checked to see if that little metal block is there and..it is, so the next logical step is to file down the trigger. I guessing the top of the metal trigger.
I'll let you guys know how it goes.

[Wrath144]

Broken wires perhaps?

[ronin49v]

nope, checked the wires and connections its an all new trigger assembly too. Thanks for asking

[Styrak]

Originally Posted by ronin49v

ok, the I checked to see if that little metal block is there and..it is, so the next logical step is to file down the trigger. I guessing the top of the metal trigger.
I'll let you guys know how it goes.

But only the very front of the top, and a mm or fractions of a mm at a time, then test.

[Jackarutu]

I’m not suggesting that any of the following applies to your current problem but it may help illustrate how you can end up with a perplexing problem with your trigger circuit.

1. Somehow I ended up with stock of some ICS wiring harnesses. I’ve never seen an ICS anything in my shop. One day I installed one in a version 2 gearbox and then drove myself crazy until I noticed that the metal part of the switch that moves back and forth when you pull the trigger is much shorter than any other brand trigger I have ever seen. Thus it barely makes connection if at all. Replaced with different brand wiring harness and all is well.

2. Tried using a trigger that came from a cheap Cybergun gearbox in a Modify Torus gearbox for a custom build. After many hours of banging my head on the work bench trying to understand why sometimes it would fire and other times it wouldn’t I came to understand the engagement of the trigger with the switch was paper thin and the trigger would pass beyond the switch and end up in front of the switch so next time I tried to pull the trigger the switch did not move forward. Changed out trigger for a Mad Bull M16 trigger and all is well with the world.

3. Trigger arching can add so much corrosion to the contracts that they become high resistance and don’t allow the current to flow but this should not be a problem with a new switch.

Cheers

[vondnik]

whitch gearbox gen

[ronin49v]

I'm going to try filing down the trigger tonight and hopefull it all goes well.
I think that's what the problem is since it is an aftermarket trigger (don't know which brand). By the way this is a Version 2 TM gearbox.

thanks guys, wish me luck.

[ronin49v]

YES! filing the trigger fixed the problem, I also put in most of the stock parts that came with the TM V2 gearbox back in.

Now I got another problem, after putting the gearbox into a TM body (Sr16 upper modified to take a one piece hopup), none of the BB's will shoot out. I looked down the bb well and can see the nozzle going back and forth when shootin. I adjusted the hopup rubber back and forth and still no BB will even go into the barrel. the hop up is a Stock plastic G&G with green rubber. When I load a bb by hand and fire the BB flies out of the well from the air pressure. I'm thinking the rubber in the hopup is too tight.

any ideas guys

[Jackarutu]

where did your air nozzle come from? Are you sure it is the correct length for an M16 version 2 gearbox?