Gearbox won't cycle.

[Muff-in]

Ok, I have built from scratch a V2 gearbox. JG gears, AR latch, Cut off lever. SHS trigger contacts. G&P m120 motor. JG Cylinder. KWA cylinder head w/ SHS nozzle. KWA piston/piston head. Some random v3 ball bearing spring guide (yes the gearbox takes a v3 spring guide). And an ~m90 spring.

I put it all together and seems to be fine. But as soon as I fire, it will cycle a couple of times then lock up. All that happens is a clicking noise and the piston nudges a little bit.

I have made sure the motor is fine. Battery is brand new fully charged.

Anyone have any suggestions for me? Things to look at? Appreciate it.

[Bishop]

I expect to be corrected when Star_Folder sees this, however could it possibly be your wiring not making contact?

[slickridley]

Cutoff lever might have been installed improperly,
Have you tried runing the box with out the spring/piston in it? just checking the gears/shim job

[Star_folder]

Did you shim your gears? Is the gearbox shell a KWA 2GX shell? Did you check how well the gears mesh with the piston?

It really sounds like a shimming problem.

[Muff-in]

I ran the gearbox with just the gears and it was perfectly fine. Hardly any noise at all. So I don't think it would be shimming. When I get home tonight I will try reshimming it and seeing if that helps. Also I will make sure the cut off lever is properly installed. And no, it's not the 2GX shell. It's a JG I believe.

[Star_folder]

While it's open, check to make sure that the piston fits in the gearbox, that it slides properly and easily.

It's probably not the cut off lever. You've got yourself a gearbox that is locking up. The clicking of your motor means that current is flowing but there isn't enough power to keep the system moving. This narrows it down to something physical is blocking the geartrain. How does the gun work on semi auto? Does it stop on it's own on full auto, it doesn't slow down or anything, it just stops while you still have your finger on the trigger?

[Dominum]

Its not a JG shell, it's likely a KWA shell of some kind seeing as it uses a V3 spring guide. A lack of excess gear noise does not mean it is shimmed well by default, a tight shim job is likely to make very little noise, especially on bearings. Is the shell black with ball bearing bushings? To add to Stars questions, when it does fire, does the motor get hot quickly? What about the wires/connectors? Does the ROF slow down before it stops cycling? Are you certain the motor is not mounted poorly?

I recommend, especially seeing as it is merely an M90, that you cycle the GB manually. Close the GB with everything fully installed, but instead of using the motor to turn the pinion gear and cycle it, use a small flathead. You should, of course, feel the pressure build the more compressed the spring is, but the gears or piston themselves should not give much resistance at all. If, when you initially begin, it is not easy to do, there is too much friction somewhere. Meaning shims too tight or something else not playing nicely.

[Muff-in]

Ok, I just took it all apart again. The shell is actually from a Cybergun M4 I believe. It's black with 8mm bearings. And it uses the V3 spring guide.

Star: When I first put everything together, I placed it into semi and fired. It shot full auto for like 6 shots then locked up and wouldn't unlock until I release the AR latch.

Dom: I will shim the gearbox pinion to bevel tomorrow and see if it makes a difference. I just need to dremel some holes into the shell as their are no pre-drilled holes for viewing the meshing of the gears. And yes, when I pull the trigger, the wires/batteries get really hot. And the motor is fine.

I'm assuming this is all a shimming problem, but I've shimmed dozens of gearboxes without a problem. So it just seems odd to me. I will try the bevel to pinion tomorrow and see what happens from there.

Thanks for the help guys.

[Dominum]

Ok, I just took it all apart again. The shell is actually from a Cybergun M4 I believe. It's black with 8mm bearings. And it uses the V3 spring guide.

Sounds like a KWA shell.

Star: When I first put everything together, I placed it into semi and fired. It shot full auto for like 6 shots then locked up and wouldn't unlock until I release the AR latch.

Dom: I will shim the gearbox pinion to bevel tomorrow and see if it makes a difference. I just need to dremel some holes into the shell as their are no pre-drilled holes for viewing the meshing of the gears. And yes, when I pull the trigger, the wires/batteries get really hot. And the motor is fine.

No need to Dremel holes, not that it is a bad thing but it will mean you will have to do a lot of cleaning. You don't have to drill holes to properly shim a GB. If the wire/battery/connectors are getting hot then Star and I are correct. Something, somewhere, is causing so much friction that the electrical component of the drive train is working overtime to compensate, and gets to a point where it cannot overcome it.

I'm assuming this is all a shimming problem, but I've shimmed dozens of gearboxes without a problem. So it just seems odd to me. I will try the bevel to pinion tomorrow and see what happens from there.

Before you bother, do what I suggested and cycle it manually, without the main spring first, then with it. You need to use process of elimination to determine where all this excess friction is coming from, and this is a sure fire way to do it.

Thanks for the help guys.

In addition to manually cycling the GB with and without the spring as I suggested, you need to test the gears individually and then two at a time, assuming you didn't when you shimmed it initially. The problem is almost certainly that at least one of the three gears are shimmed too tightly, or that two or more of them are shimmed so as to scrape upon each other. If not, it is the piston or the motor that are too tight. Remove the piston and close the shell, spin the gears with the shell fully closed and while having the selector plate in the auto position. There should be minimal resistance, all three gears should spin in tandem easily. If not, there's your problem. Now you have to figure out which one, or more, is the issue. No need to drill holes, you have plenty of viewing space via the holes already part of the shell. Do the same thing you just did with each of the three gears, but one at a time. See if they all spin easily when in there by themselves. If they do, then try two at a time to see if two of them are shimmed so that they apply friction to each other. Using this process, you will eventually figure out where all this excess friction is coming from.