[CM048S] Piston head bearings stuck, piston not travelling, cylinder head/nozzle questions (Spring issue fixed)

[Xedilian]

NEW ISSUES HERE

ISSUE #1 : The 7 tooth SHS piston I ordered and the SHS piston head don't slide freely in the gearbox. Did a piston check, cylinder and piston only even, to rule out the head. No change. It becomes very hard to move the piston by hand.

ISSUE #2 : The ball bearings of the piston head are stuck inside the piston. They do NOT move freely AT ALL, so far I have failed to get them out.

ISSUE #3 : I ordered a LONG V3 cylinder head, which doesn't fit, because well, it's too long.
The stock head is a V2 type, so i'm assuming the nozzle is as well.
The long V3 nozzle is the same length as the stock "V2" nozzle.
So far what i've figured out is that I need a V3 SHORT cylinder head and a LONG V3 nozzle. Does that make any sense?


OLD ISSUES (SOLVED)
Hey gang.
I bought this CM048S almost brand new. I don't know what the stock spring is in there, all I know is it shoots around 450fps, so, way too hot.
I can confirm that with a fully charged 8.4V 3A1200MaH battery, the stock spring fired perfectly. No complaints there.

I bought a SP110 to bring my FPS down, installed it (I will spare you my hate story with V3's), and as I cycled, (with the same fully charged battery), it cycled to 95%, and didn't move an inch more.

So the spring is compressed, maybe a couple gear teeth away from releasing, and the motor wants to push, but the gears are locked up, making this clicking noise when i pull the trigger.
The battery also gets very hot. The wires do not.
Removing the motor, I try manually turning the gear, they are hard to turn, and as I almost complete the cycle, something blocks me.

The only way to reset the cycle is to pull on the anti-reversal latch.

I've read a bit on the issue, some say you need a better motor, some a better battery, or the spring is the issue. Considering the stock spring is supposed to be stronger, I doubt any of these are the issue here.

I re-did the shimming and the greasing, and there were no grinding noises, no snags, and just enough room for the gears to move.
There's also this annoying CLICK CLICK noise when I go to pull the trigger allllll the way. A spring? Doubt it has anything to do with this.

I CAN DO VIDEOS! If that helps.



TL;DR : Gearbox wont cycle fully, gears jam. Halp.

[pestobanana]

The issue may be that the spring is too long. CYMA gearboxes have a gigantic washer inside the piston which raises the FPS. That's why CYMA AKs usually get 350 on a SHS M90 and 400 on a SHS M100.

[Sandman2749]

I just reassembled my M16A3 several times last night. Something in the gear box wasn't lined up properly so the first two times it wouldn't cycle.
No idea on your skill level with upgrades so just a shot in the dark here.

Maybe try a realignment and one more attempt to get it to work.

[Xedilian]

Originally Posted by pestobanana

The issue may be that the spring is too long. CYMA gearboxes have a gigantic washer inside the piston which raises the FPS. That's why CYMA AKs usually get 350 on a SHS M90 and 400 on a SHS M100.

I haven't paid much attention, but they seemed to be almost identical in length. The piston DOES have some weird looking design. It's one of those with the screw on the outer end instead of on the inside. It has some metal retainer (i guess) inside the piston.
I believe this is what you're talking about.
Therefore, new piston?

[EOD Steve]

Are the ends of the new spring tapered flat to mate with the piston and spring guide?
Inability for the spring to rotate may cause the coils to contort, seizing up the piston.

I would simply try swapping in another spring before throwing money at problems.

[Xedilian]

Originally Posted by EOD Steve

Are the ends of the new spring tapered flat to mate with the piston and spring guide?
Inability for the spring to rotate may cause the coils to contort, seizing up the piston.

I would simply try swapping in another spring before throwing money at problems.

I'll let you be the judge of that.
They're not the same length, but the spring rotates fine on the spring guide.
Rotating the spring into the piston counter-clockwise goes smoothly. Rotating it clockwise (Backwards for the spring) has the spring snag into the hole in the piston head there. Not always, but sometimes

20150723_154851.jpg
20150723_154856.jpg
20150723_154942.jpg
20150723_155207.jpg

[Xedilian]

I think I found the problem.

Looking more closely at the piston and piston head, there is about a half an inch of metal sticking inside the piston, and it seems to be the little space I need to fully retract the spring.

Therefore, let it be known that if you have this problem, check your piston head.
This stock stuff needs to be changed.

[ThunderCactus]

You should also change that battery anyway. The stock 1300mah batts are downright garbage, well known for extremely poor performance.
a 7.4 lipo will give you more steady performance as the battery drains, as well as you might be able to get it in a 1600mah

[Xedilian]

Originally Posted by ThunderCactus

You should also change that battery anyway. The stock 1300mah batts are downright garbage, well known for extremely poor performance.
a 7.4 lipo will give you more steady performance as the battery drains, as well as you might be able to get it in a 1600mah

I'm not versed very well in lipo's apart that they catch on fire if you let them charge too long. The wiring got hot when I tried running a 9.6V in it, leading me to believe it might need to be changed as well.
Would a lipo still be safe for the wiring?
There's also the matter of the stock small tamiya connectors, the lack of space under the top cover, etc. It's one of those folding skeleton stock AK's.

[pestobanana]

Originally Posted by Xedilian

I think I found the problem.

Looking more closely at the piston and piston head, there is about a half an inch of metal sticking inside the....

Originally Posted by pestobanana

The issue may be that the spring is too long. CYMA gearboxes have a gigantic washer inside the piston....

Hmmm

[Hectic]

That's funny. I had this issue with my cyma mp5. I ditched the old head and that 1/4 lb of pot metal ( obviously not that much) in the front for a regular head and it all fit great. Worked out cause I was going for high speed so I needed to lose the weight anybow

[Xedilian]

Thinking of going with lonex piston / piston head combo. Have to make sure the stock gears are the right width. If i'm not mistaken, this is a hybird VFC/LCT clone.

Does anyone know if all of this will fit together?

Modify SP110 spring
Lonex extreme toughness (red)
Lonex POM Piston head
Stock V3 VFC-clone gearbox

OR I could go for SHS 15 teeth piston
OR I'll just make a new thread for this whole thing.

Thanks for the help guys

[Styrak]

Gear width vs piston width is not something you have to worry about. Unless for some reason you mistakenly tried to put a half tooth piston with full tooth gears.

[Xedilian]

Originally Posted by Styrak

Gear width vs piston width is not something you have to worry about. Unless for some reason you mistakenly tried to put a half tooth piston with full tooth gears.

NEW ISSUES HERE

ISSUE #1 : The 7 tooth SHS piston I ordered and the SHS piston head don't slide freely in the gearbox. Did a piston check, cylinder and piston only even, to rule out the head. No change. It becomes very hard to move the piston by hand.

ISSUE #2 : The ball bearings of the piston head are stuck inside the piston. They do NOT move freely AT ALL, so far I have failed to get them out.

ISSUE #3 : I ordered a LONG V3 cylinder head, which doesn't fit, because well, it's too long.
The stock head is a V2 type, so i'm assuming the nozzle is as well.
The long V3 nozzle is the same length as the stock "V2" nozzle.
So far what i've figured out is that I need a V3 SHORT cylinder head and a LONG V3 nozzle. Does that make any sense?

[ThunderCactus]

Lipos have higher amperage which equates to higher torque at the motor.
lipos are perfectly safe when handled properly, they only catch fire when charging if they were previously damaged.