Jump to content
Sign in to follow this  
Rogerborg

SOLVED: CYMA M4 gearbox doesn't want to come out

Recommended Posts

All the pins are out and cables are loose, and the gearbox is free to come out.

 

Except the receiver seems too small to allow it.

 

Sliding the gearbox as far forwards as possible, the rear is still a good 5mm inside the receiver.

 

rRFqerB.png

 

 

OK, so let's tilt the gearbox up and take it out at an angle.

 

Note the lip on the receiver where the bottom of the gearbox can slide into if I can... just... get it ... another 5mm....

 

rLbENqW.png

 

 

OK, it's in.

 

oXiSXzg.png

 

But that just locks it in even worse at the back of the receiver.  Not 100% obvious, but there's no way it's coming out any further, it'll snap the back of the trigger guard / handgrip mating surface for sure.

 

OzvIbxv.png

 

I assume it was shoved in by main force, but taking it out that way feels like the (plastic) receiver will give way before it come free.

 

I've watched some disassembly videos and none of them have receivers with this kind of death grip on the gearbox.

 

Am I just being a pansy about it, or is there something that I'm missing here?

 

Share this post


Link to post
Share on other sites

Take a photo of the whole receiver side on , both sides, just to check if there is anything obvious you have missed.

Share this post


Link to post
Share on other sites

You want selector switch at about 11 o'clock or there abouts

(Semi being 12 o'clock - so between safe & semi)

 

After removing the 2 main allen key pins

remove the tiny gearbox pin above the trigger etc....

 

The plastic lugs at back of receiver is a bitch

these two plastic lugs are a pain - place selector at about 10:30 - 11 o'clock

pull the gearbox forward & upwards - it takes a yank

file the bastid lugs down a smidge to help replace/remove box in the future

f*ck knows why Cyma cast this extra lugs - you don't need them to hold box better

it just makes it bloody difficult to remove

I'm sure I mentioned this in the CM515 write up I did - is a bitch to first remove....

 

Quote

One thing I will say about receiver and removing box....

There is like a little lug of plastic on top of lower receiver than restricts the box coming out a little and needs a little wiggle

the box comes out eventually and is a bit of a squeeze getting box back in but went in ok in the end

When I had to remove spring guide coz it was shooting a tad too hot....

On refitting the box back and wiggle squeeze the selector plate broke going back in but had a spare one luckily

So it might be worth filing down a 2mm bit of plastic carefully to allow box to go back in/out a little easier

box is affixed very well in receiver with the pins - allen key types but they hold it together just fine

 

file down the lugs, you don't see the raised lugs at all, just a pigging pain imho

They don't even tightly retain the feckin box - just a pig to remove

 

I found out the selector plate/switch helps if you have it at about 11:00 o'clock ish than midnight

coz the sod broke on my first cyma refitting it a second time after spring guide in/out scenario

probably a flukey bit of bad luck but hey ho I place the sod at 11

Share this post


Link to post
Share on other sites
19 minutes ago, Sitting Duck said:

You want selector switch at about 11 o'clock or there abouts

(Semi being 12 o'clock - so between safe & semi)

 

The plastic lugs at back of receiver is a bitch

these two plastic lugs are a pain - place selector at about 10:30 - 11 o'clock

pull the gearbox forward & upwards - it takes a yank

file the bastid lugs down a smidge to help replace/remove box in the future

 

 

Winner winner.  Thanks all! 

 

Yes, those lugs really do make it egregiously difficult, I wasn't imagining things and did have everything correctly removed.

 

A fiddle with the selector and a non-pansy heave straight forwards did it - not pushing the motor face of the gearbox up as I'd seen on several how-tos.

 

You'd better believe I filed those lugs off before putting it back in, and even at that, it took a little struggle.

 

As it turned out, the gearbox was shimmed pretty damn well as stock, so it was a fairly pointless exercise. For form's sake, I added 0.1mm to the motor gear to take out a bit of slack, but the other gears were already spot on.  Other than replacing the Chinagrease and doing a tentative radiusing, there wasn't much to do in there.

 

I'm waiting for the other shoe to drop on this gun, but it's surpassed my modest expectations so far.

 

The only thing I can find to bawww about is that the wires from the battery look nice and fat, but past the fuse they used thinner ones.  That's fairly nit-picky though.

Share this post


Link to post
Share on other sites
1 hour ago, Rogerborg said:

You'd better believe I filed those lugs off before putting it back in, and even at that, it took a little struggle.

 

As it turned out, the gearbox was shimmed pretty damn well as stock, so it was a fairly pointless exercise. For form's sake, I added 0.1mm to the motor gear to take out a bit of slack, but the other gears were already spot on.  Other than replacing the Chinagrease and doing a tentative radiusing, there wasn't much to do in there.

 

 

File the lugs off - even a little inside at a 45 degree angle on the two lugs....

The slight fiddle is fairly normal, but you kinda get the hang of a wiggley knack of most AEG stuff

 

Yup shimming isn't bad on the box - I could have told you that before hand

(think the bevel is shimmed about 0.25mm - underneath really doesn't matter as pinion keeps it from dropping)

The slight shrilly sound is more down to the china gears & pinion on the lame ar$e stock motor

Both the Cyma & the std Grey G&G 18k motor are 27/28 tpa which means it sucks speed wise

 

The Cyma china gears don't really run that smoothly tbh

even if you clean up the gears of green gunk, bit of silicon oil on axles and spin the gears etc...

They don't really run buttery smooth like other gears like SHS or even one or two other stock sets

They are very chunky so will not strip a tooth easily - but could be a tad smoother but hey ho cheapy china gears

 

The motor is crap - it has a D-pinion, the armature tpa @ 27/28 is too high

Yes could be used for a frankentorque motor but most admit these FT motors are not really the be all & end all

(Even on most 330fps DSG's or even DMR's a max 22tpa torque neodym motor will be plenty)

So really the 27/28 tpa stock motor is perhaps a worthy upgrade at some point

OR

Run the thing on more juice to get more response perhaps but long term contacts can wear quicker

(worth noting cyma trigger switch is slightly slightly different - the mount hole is bigger than SHS)

 

It is a decent gearbox/gun for the money, the higher speed gears need the gearbox modding to fit

Not Cyma's fault - numerous re-enforced boxes won't let you fit 12 or 13:1 gears straight in

The tappet plate has slight cut-outs, but so does the Lonex too & people rate (maybe slightly over-rate those)

The safety needs the screw removed prior to opening, the V2 gearbox has a V3 spring guide

Qwirky - but works and quite robust

 

The pistol grip - fits well, it doesn't need any modding like some long grips need filing down etc...

the motor plate could be better, the motor plate is a small disc type with allen key - normal cheapo plate

Could be fitted with M3 bolts instead of self tapping screws but c'mon it is a £70 gun ffs !!!!

 

The wiring is quite decent tbh, but so far I've ripped out the std wiring when I fitted mosfets

Though std wiring is fine if you fit a mosfet using existing loom

If you fit deans over small tamiya connectors that is the easiest/cheapest upgrade to do or worth doing first

(you can even re-use the deans if you rewire at a later date - but std wiring is decent)

 

Like most budget guns, the piston, cylinder head, nozzle & AoE could be improved

Piston head is ok - no really it is but has a chunky heavy metal mount inside the piston and a screw

(o-ring seal is a little bit crap like many stock guns)

Piston is ok - could upgrade at some point but tbh you could wait until it strips

Cylinder head - ok but AoE could be corrected as per usual, f*cking loose fitting though - few wraps of ptfe wrap

(but is loose in stock cylinder)

nozzle is a clear non o-ring type as per usual, SHS red M4 nozzle is quite loose fit on clear cyma tappet plate

So might need to upgrade/change tappet with a mod cut out with a SHS nozzle or look for another nozzle make

If/When correcting AoE then v3 bearing spring guide will replace slight drop in fps from slight shortening of stroke

 

This is all the normal basic tweaky crap in nearly all AEG's - not a big major must do now thing at all

Wait until fps drops or things go pear shape, then open her up and fix/improve stuff as needed

I say this as very often - in fact nearly always there is more attention required than just slapping in stuff

Slightly qwirky box but nothing major at all

 

The box is tiny bit shrilly but most of this is down to cheap motor/pinion and cheapo mass produced stock gears

chunky but they are not smooth running SHS gears - let alone siegetek gears

Spur can be a bit tight if you upgrade - little slack, so might need to replace bushing with 8mm bearing on TOP

This will give you a wafer more slack, might need a thin shim under spur and next to nothing on top of spur

(watch for spur rubbing on other two bushings as it needs to get shimmed lower)

This lack of room on spur gear on higher speed gears is down to thick chunky 8mm bushings

Good but there isn't bundles of slack/play for shimming thicker gears up easily

(normal shimming stuff but a bit less room than say a G&G box imho - nothing major though)

 

The gun represents great value for money - but and it is a massive sumo wrestler butt....

Be very careful just how nutz you go upgrading stuff - even if you do it all yourself

Many times the risk of screwing it up or making it worse will outweigh the cost in time/money

Plus it will still be a cheapo china gun - even if you do make it sing

 

Use it for what is, mess with it when it needs it or if it busts then scrap it for spares or bin it

I've wasted lots more than just £70 or so on my bad first few choices

 

Think the wiring at back is a more flexible or semi flex silicon wire to make a bit more durable

When bending the connectors back in the stock than the stiffer coating wire inside the gun's box

think it is just the type of insulation on the wire - I've seen much worse flimsy wiring looms

Share this post


Link to post
Share on other sites
9 hours ago, Sitting Duck said:

Yup shimming isn't bad on the box - I could have told you that before hand

 

I was in there for the joy of it, really. Still, it was a nice surprise.

 

 

9 hours ago, Sitting Duck said:

Run the thing on more juice to get more response perhaps

 

If I were to stick with nimh but up the voltage from 8.4V to 9.6V would I be likely to get a quicker response?  I'm only planning on using it for CQB in semi-auto, but minimising the time between trigger pull and pew would be good.

 

 

9 hours ago, Sitting Duck said:

The pistol grip - fits well, it doesn't need any modding like some long grips need filing down etc...

 

But I took a little off the top anyway, just to be sure that it was solidly on the gearbox and not being held out by the receiver. I don't think it was, but the only way to be sure is to create a tiny gap, yes?

 

 

9 hours ago, Sitting Duck said:

(o-ring seal is a little bit crap like many stock guns)

 

I stretched the O-ring over the cylinder and heated it a little.  Might be voodoo.

 

 

9 hours ago, Sitting Duck said:

Cylinder head - ok but AoE could be corrected as per usual, f*cking loose fitting though - few wraps of ptfe wrap

 

Wrapped.

 

 

9 hours ago, Sitting Duck said:

Wait until fps drops or things go pear shape, then open her up and fix/improve stuff as needed

 

That's the plan.  I'm not intending to throw a lot of money at this gun, I really just wanted to see what it was like inside.

 

If I stick with airsoft, I'd probably buy something higher end, and then stubby the CYMA down - this looks hilarious as a side arm:

 

 

 

Share this post


Link to post
Share on other sites
Quote

I was in there for the joy of it, really. Still, it was a nice surprise.

 

Sounds like a smutty line the bishop said to the actress....

Seriously - better understanding of it all next time you open it up

if all ok then no harm done & wisdom gained blah x 3

 

Quote

If I were to stick with nimh but up the voltage from 8.4V to 9.6V would I be likely to get a quicker response?  I'm only planning on using it for CQB in semi-auto, but minimising the time between trigger pull and pew would be good

 

Yup could do but don't pay through the nose for batteries - especially nimah's

If you invest in more batteries then at some point the jump to LiPo will happen

If chucking money then a SHS HT or RA HT motor from ak2m4 is about best way of getting more snap

but that is a chunk of £28 - DO NOT BUY A HIGH SPEED MOTOR imho

the SHS is not quite a 22tpa torque but a blance of good torque & speed at nearly 30k (16tpa)

not too crazy like a HS motor that draws way more amps etc....

But definately provides more wallop for running on 7.4v lipo's etc....

 

ZCI torque is 22tpa and not much quicker than a stock motor imho - SHS/RA HT is the one

ps I'm not on commission btw, I'd recommend beluga caviar to grease the box if it worked but it don't

 

 

Quote

But I took a little off the top anyway, just to be sure that it was solidly on the gearbox and not being held out by the receiver. I don't think it was, but the only way to be sure is to create a tiny gap, yes?

 

Yup, on many stock and very very often some aftermarket grips they can be too long hitting receiver, throwing out height/angle

But cyma is a quite good by comparison and is about right

In fairness most guns stock grips "should" fit very well BUT there have been some like G&G G26 or something which wasn't & needed quite a bit filed off on some gun

A wafer thin gap ensures the grip is fitted correctly to box not skewed out a whisker hitting the receiver

but you don't want a gaping gap allowing crap to enter the exposed bevel bushing/bearing

 

Quote

other o-ring/ptfe stuff etc....

 

Yeah - usual cheapy tweaks & stuff that is worth a go tbh

some/most guns out of box can do with better seals & stuff

But fps will always deplete, seals wear, springs fade etc....

It is all part of $hit happens - fps doesn't improve or get better like fine wine

Should get a small increase in fps but be careful you don't go too hot

Some guns like SRC I opened, over volume sometimes to compensate for crap seals

End of the day they are usually just slopped together by Chinese piece workers by the hour

(so hardly a precise ultra high end pieces of engineering perfection)

 

The experienced you gain helps you improve your own tech skills

The more you do the more you learn etc....

Tech or opening a box is like riding a bicycle in some ways

no matter how much you read or watch often you just gotta get on it and somehow work out that balance yourself

(Helps if you have half a clue what you are supposed to do but you get what I mean that you learn by doing)

 

Rex Kramer:

Quote

All right, Striker, you listen, and listen close. Flying a plane is no different from riding a bicycle; it's just a lot harder to put baseball cards in the spokes.

 

Image result for Airplane rex kramer

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×