Piston Cycling.

[T_A_N_K]

I have a Systema Drop in V2 mechbox, originally the mechbox seemed to have a messed up gear ratio so I replaced them with a set of Modify Torque ups and now I have another problem and Im totally stumped.

Mechbox fires fine on semi, but on full auto it makes a weird noise when it finishes cycling. I have tried 3 different motors, including a EG 700, G&G Motor, and a Systema Magnum. Spring is approximately 300fps.

From what I observed, it seems like piston is returning to the forward position sometimes slowly and sometimes the piston protrudes about 3/4 of inch in the rear opening like so. By slow I mean I can see the piston at its cocked position and return slowly to the forward position.



I have not tried to see if it feeds. I'm ready to whip this thing out the window.
Any thoughts?

[Styrak]

Not enough lube? Or anti-reversal latch is somehow screwed up?

[T_A_N_K]

I don't think that's it, because, technically, if the piston is going from cocked to decocked, then according to the picture, the sector gear should not have teeth engaged to the piston right?

If that's the case, even with no lube, a 300 fps spring should have no problems pushing the piston back the forward position, at least I would think so.

In regards the anti reversal latch, the issue I had before was the bevel gear only had two grooves in it, and we believed it was causing the gears to go reverse to a point when the piston cycled (at least we thought so). I changed the gears out and the modify bevel gear has 6 grooves in it.

[zone 69]

Maybe check your shim job, you could have to many shims and the gears are not spining freely.

[m102404]

Be sure that the AR latch isn't biding with the mechbox nor with the bevel gear.

Without the spring/piston/etc...in the mech, and with the mech all screw together, you should easily be able to manipulate the latch into and out of position.

[Kos-Mos]

I would say, open the mechbox again, clean everything (use some brake cleaner stuff. The one I have is Wurt and does not attack rubbers or plastics). Then check for debris, deformations of casting errors/bumps.

All I can see is that the mechbox shell was casted wrong, and either the rails are not aligned with the cylinder or there is a bump somewhere along it that cause too much friction.

Also look on the piston rails to see if there is a mark on the rails, or a spot with no grease at all. That can be the sign that the mechbox rails are binding.

Check for deformation in the cylinder/piston head too It might be a simple bend caused by the machines when they did it, and since the mechbox probably cycled once or twice, it passed QC.

Good luck, and if you don't find what is it, throw it at me instead of the window.

[milehigh]

From his original post, it sounds like this problem occured after the installation of the new gear set- thus likely ruling out the chances of it being a gearbox issue. Did you install the modular gearset? As I recall, they've got their own anti-reversal latch which could be the problem.
Pull it apart and remove all but the gears and anti-reversal latch and fasten the two gearbox halves together. The gears should spin freely and you will hear the ant-reversal latch clicking on the bevel gear. Also reach inside with a small screwdriver to see if the latch has free movement.

To me it sounds like the problem lies with that latch. Do some investigating and let us know!

[damage]

Here are my theories.
-Something to do with AOE(angle of engagement). Sector gear and piston.
-M100 and 7mm bearing bushing. Gears might be over spinning caused by a large battery and high torque motor.
-AR spring is weak or AR itself is binding in the gearbox. AR should move freely.
-or mail it to me I'll figure whats really wrong with it