Piston Jamming

[Boyso]

Well I ran into a new problem today.

In my gearbox, I have

MASK Piston Head, Cylinder Head + Modify Piston (The MASK full kit)
Stock Cylinder, Nozzle, Tappet Plate
Modify S90 + Modify Spring Guide

Everything else is stock.

I did shim, oil everything, like the piston rails. Manually, it slides correctly without much resistance.

When I test fire, the piston just slams back and stays there. When I open it up, of course, parts fly everywhere.

I read other threads, trying to swap the bearing spring guide back to the stock one. Without success.

What's wrong? Is it the combination S90 + Mask?

Thank you very much, I've been opening and closing my gearbox for 3 hours now.


EDIT : Just tested moving the stock piston inside by hand. It does move much much more smoothly. The Modify one seems to catch at one spot.

Should I install the MASK piston head on the stock piston, and remove the second last tooth on it?

[Amos]

Did you remove the last tooth on the piston?

[Boyso]

The modify one came with the tooth cut off.

I just cut the tooth off the stock piston. Going to try it right now.


EDIT : IT WORKED! Thanks, yeah, the Modify one (http://www.airsoftparts.ca/store2/in...oducts_id=1369) doesn't fit properly in my JG gearbox. Or, it might be because the JG stock one is soo oiled/greased it runs more smoothly.

[Amos]

Glad you figured it out,

Remember, grease the piston rails and gears... the only place oil should ever be used is in the cylinder (but instead I use ARS silicon grease lol)

[Boyso]

I used the G&P oil + grease kit.

Silicon oil (Quite runny)
"Bearing Grease"
Gear Grease

I used the "Gear Grease" on the gears (DUH) and on the rails.

I used the "Bearing Grease" (Seems to be Silicon oil, but a bit thicker, maybe Silicon Gel.) on the cylinder head/nozzle part as the stock nozzle with the Mask Cylinder head (Believe it's a Modify one) wasn't smooth.

I used oil on the o-rings and inside the stock cylinder

One thing I just noticed, (maybe it's because my M4 is in 2 halves and I'm dry-firing to adjust motor height) but it doesn't seems quiter for now. Maybe when the gun is closed AND shooting BBs, it will be better.

Anyway thanks for the help, and sorry for cluttering the section, with a problem I figured out.

[Amos]

Sounds like you've got a good understanding of what goes where! (you wouldn't believe some of the things that I've got... I've actually had AEG gears that were lubricated with automotive engine oil)

The MASK kit will quiet everything down once it's assembled and firing BB's

[Boyso]

Originally Posted by Amos

Sounds like you've got a good understanding of what goes where! (you wouldn't believe some of the things that I've got... I've actually had AEG gears that were lubricated with automotive engine oil)

The MASK kit will quiet everything down once it's assembled and firing BB's

I opened up my gearbox so often today, I think I have now the same experience as a person with 1 or 2 years of experience. :lol:

Everytime it jammed, I hurried up to dissassemble it as I was scared it would break more. Then, every part flew across the room, and had to reshim every single time.

Aaah, airsoft.

[coach]

Watch those mechnox screws. They strip easy especially when you get frustrated from opening them so much so frequently.

I almost opened the door and threw someone's mechbox across the street on one build. The thing was haunted and jinxed. Ended up passing through 4 different peoples work bench. Owner was a cheap bastard using inferior (borrowed/loaned/cheaply acquired) parts.

[audi_bhoy]

The problem was probably due to the piston being bigger than the space it had to move into, I had this same issue with the white modify piston in a G&G gearbox, as the gearbox had flats and the stock piston had 8 sides instead of being round, like the modify. I filed down the modify piston and it doens't stack anymore.

[Boyso]

Originally Posted by audi_bhoy

The problem was probably due to the piston being bigger than the space it had to move into, I had this same issue with the white modify piston in a G&G gearbox, as the gearbox had flats and the stock piston had 8 sides instead of being round, like the modify. I filed down the modify piston and it doens't stack anymore.

Yeah I might try that when I re-swap spring.

Won't be soon though! :P

[Boyso]

Update,

My gun went fine and I was able to fire about 5 BBs. Then, *click* *click*. Was pretty late, so I just went to bed, thinking my battery simply need some rest on the charger.

Tried again the next day, still a clicking sound. Aah, shit, maybe gears or anti-reversal are misplaced! Opened up the gearbox, to find the gears and AR sitting there neatly. But!

The Piston was slammed back again. Took it out. It was ugly.

Piston head (Yeah, the Modify one, on a Modify piston) broke off the piston, leaving plastic bits everywhere. Scratched my cylinder head too.

Took everything out, reshimmed again (of course since everything popped out when I tried to remvoe the jammed piston), regrease/re-oiled. Filed down my piston much more, to find out the stock one really fit more nicely. The part underneath the piston head, where you screw, is the part that broke. I was able to re-screw, but it may be not as strong.

I installed the piston head on the stock piston, which moves freely on the GB rails.

So far, It works, but I think my battery needs replacement. BBs aren't flying more than 10 feet and can't even go thru a soda can from point blank.

So now, my question is (finally) :

If I want a new battery pack on cheapbatterypacks.com

I've selected the 8.4V with the "Odd Double" shape for M4 S-systems.

So now, for the cells. I've been recommended the Elite cells, but which ones? And some seems not to be the same size? It's pretty tight in my M4, can't fit much bigger than the one I have right now. "Golden Eagle" 8.4V 1100 mAH.

Last question, wire size?

Thank you very much!

[CJay]

battery aint gonna make any difference to ur FPS bud - U got a compression problem somewhere which means when u chewed out yer piston something pretty crucial got messed up.

I'm gonna say the pistonhead needs replaced at least with the type of damage u described above, maybe even ur cyllinder head. u may have just destroyed the o-ring on ur pistonhead so check that first. My money is on a cracked piston head though - may have sheared through where the front and rear disc join and leaking air somewhere in there - probs not even visible to the naked eye.

sorry to be the bearer of bad news but the battery is the least of ur worries right now hehe. I know because I've don the exact thing ur describing a couple times, only diff is the second time the pistonhead shattered lol

Oh and welcome to airsoft!!!!!!!!!!!!!! lol

[Boyso]

Originally Posted by CJay

battery aint gonna make any difference to ur FPS bud - U got a compression problem somewhere which means when u chewed out yer piston something pretty crucial got messed up.

I'm gonna say the pistonhead needs replaced at least with the type of damage u described above, maybe even ur cyllinder head. u may have just destroyed the o-ring on ur pistonhead so check that first. My money is on a cracked piston head though - may have sheared through where the front and rear disc join and leaking air somewhere in there - probs not even visible to the naked eye.

sorry to be the bearer of bad news but the battery is the least of ur worries right now hehe. I know because I've don the exact thing ur describing a couple times, only diff is the second time the pistonhead shattered lol

Oh and welcome to airsoft!!!!!!!!!!!!!! lol

Yeah but I inspected everything. Piston (Modify one) was the one that stucked, and I switched for the stock one. Piston head seemed to be fine, and the O-ring was intact as I remember putting more oil on it.

But yeah, I may bring it to a Gun Doc, tired of opening it up simply to find more problems than before.

[CJay]

might look good but like i said could be a tiny crack u can't even see till pressure builds up - I could be totally wrong though - like ya say u really need to check it out and rule out all the options - I just kinda listed the most probable given the damage it sustained. even if the pistonhead looks good it might be leaking - same with cyllinderhead. Think u'd do urself a big favour takin it to a gundoc like ya said hehe. but hey don't be discouraged - talk to anyone around here who works on guns and they'll have multiple stories of hexed gearboxes and phantom airseal issues, yer by no means alone so don't feel bad

[Boyso]

Who would've thought that.

Compression is better with the stock cylinder head in the stock cylinder than with the Modify one.

Anyway, gun is shooting sub-300fps with the S90, which is fine for my indoor needs.

Now, just gotta figure why it keeps firing auto-only. Cut-off lever seems fine.

Gotta love these clones!