AOSC Forum Archive

Ok guys, I have almost completely finished my DMR build. Yesterday I received my M150 spring in and put it into my KWA 2GX Gearbox. Once I put it all back together and put in the motor, I pulled the trigger and realized that it isn't possible for the piston to move back enough to finish the cycle. So when the piston is pulled all the way back, it just locks up and the motor isn't able to pull it back any more.

It's not a motor problem (using Lonex Orange High-Torque) and it's not a battery problem.

I know that there are several ways I can fix this. But I want your opinion on what is the best way.

Should I short stroke the gears and piston by 1 tooth? Should I shorten the spring? Get rid the of the bearings on piston head/spring guide? Oh and I also have a 1/4" Sorbo and the stock cylinder head padding as well to fix the AOE.

I would start by ditching the bearings.

What battery are you using?

This is a classic "not enough torque" issue. It's either your motor (unlikely), your battery (possible), or a mechanical issue. Did the gearbox function properly with the lower powered spring? You should check your shimming as well. If it's shimmed too tightly it won't be able to cycle properly.

You should also check to make sure that your piston can easily move all the way to the back of gearbox.

What all upgrades do you have for the gun? And what spring did you pick up?

Ok I will start with the bearings then.

And Star, using a Turnigy 11.1v LiPo 20C. Yes the gearbox functioned perfectly with an M130 spring before. Shimming is perfect, that's always something I put a lot of effort into.

As for the upgrades in the gun: SHS 15 tooth piston (2 teeth removed for AoE), Lonex POM piston head and pretty much everything else stock. Oh and its a SHS M150 spring btw.

Torque shouldn't be an issue, I just think that it's a matter of the spring tightening up as much as it can before the gears can fully cycle. I can see the spring through the holes on the piston and it's TIGHT. All the coils on the spring are pressed up against each other as tight as possible. I'm not sure is this is normal but sure doesn't appear to be normal.

When I get back from work I will remove the bearings and see what happens from there.

Thanks.

hmmm, that is interesting and unusual. I hardly ever run a gun without bearings on both the spring guide and piston head, and I've never had a problem with springs binding like that.

Do you think it would be a problem if I took the bearings off? I only shoot in semi.

You don't need bearings on both the piston head and spring guide. They only NEED to be in one place or the other. Whether it's the piston head or spring guide really doesn't matter, but generally, it's easier to remove them from the piston head.

For the record, I've had spring binding problems in 3 separate gearboxes with SHS M150s and M160s.

Does it cycle fully in full auto?