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Cyma Cm.621 Upgrades


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bugger it will stick with the low compression loool im not willing to spend anymore just now haha will wait on the motor gear and bearing coming in hopefully tomoz and get her back together and leave her be lol aslong as she runs hits 320fps then shes geting left lol

wanna start buying in my face and head pro then tac so can start saving for my future build or a higher end rif lol

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See this is how it begins.....   It'll be 13:1 short stroked before it ever hits the field   It can be a rewarding thing getting a gun running sweet especially if you do it with c

I never mess with any of mine unless I really really really have to 😏   

good points there   fuck me - prommy buckings are quite bad too must be the Leslie Ash of bucking lips...     think there is lesson here that applies to airsoft too

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WTF ???

 

PM-4571443167606b.jpg

 

Now don't get me wrong, fancy high end shit is all well & good

if you got money falling out of your arse & all that

and some Youtuber's build hose machines almost as big as their fucking ego

 

and yes ultra high parts are manufactured to higher tolerances blah blah blah

and a CNC box owner will obviously say it is the best

(fucking hope so for the money you paid for it)

 

But there is also the classic newbie mistake of slinging in the most expensive parts

without checking how they all fit & operate together

(if you ain't checking = you ain't teching)

 

They sling in stfu bits n bobs - the very best/most expensive bollox

lonex gears or Seigtek for example...

sling it all in and it don't work too well or pretty piss poor

 

But REALLY...

pic again...

 

PM-4571443167606b.jpg

 

if you don't fucking know which fucking gear goes where

and you need a diagram on the cunting expensive as fuck box to tell where expensive shit goes

then you really should just send it all off to somebody else to build for you imho

 

fuck me - looks like IKEA are making airsoft parts now

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haha i know what your saying lol nah ive looked into that box and seems not to bad was more the being able to access the gears trigger etc without having to take apart the full casing lol that drew me to it as for cost aye its expensive lol  and like i said wa one i spotted nothings definite for the future build other than asthetics in that it will be m4 based lol :)

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12 minutes ago, miserydrift said:

bugger it will stick with the low compression loool im not willing to spend anymore just now haha will wait on the motor gear and bearing coming in hopefully tomoz and get her back together and leave her be lol aslong as she runs hits 320fps then shes geting left lol

wanna start buying in my face and head pro then tac so can start saving for my future build or a higher end rif lol

 

think most people look to tear down a gun once she dips below 300fps

(as a general rule of thumb - unless you are perfectionist trying to maintain constant range/performance)

 

nozzles will never seal 101% like say cylinder head

coz they are shuttling back n forth but unlike piston

they don't swell outwards from vents in piston head etc...

 

so nozzles will never seal 101% & if it is too tight on spout

that isn't ideal either for rapid shuttling back n forth

 

now yes it is gonna leak if it is really loose & not ideal

but you have lessened the leaky as fuck cylinder head

so though you may not reclaim say 30fps

you should perhaps see 10fps or so at least improvement

 

and the issue with all this shit is where do you start & where do you stop ???

I said they are a bit bespoke/qwirky - but they are pretty decent cheapo starters

just a bit less TM Compatible in some places

 

I mean yeah you could buy a new cylinder head that std nozzle might fit better

and also a new nozzle/tappet combo & mod it a little (pita Cyma)

 

But really I think your approach is right atm

maybe further down the line if fps drops or it shits the bed

then open her back up when it needs it and do the nozzle/tappet thingy perhaps

 

I can pm Pete about sending him a Cyma tappet to try his nozzles on

but think most of them will still be a little loose on the Cyma tappet

fucking annoying coz the Cyma v3 boxes/tappet are more compatible

it's these fucking v2's that are a little weird...

 

the 516 is a v2 gearbox - but uses a v3 spring guide (thicker tab at back)

the safety arm - have to remove screw before you open box

the tappet plate has the cut outs up front that most don't have

the ye olde trigger switch has a big eyelet or mod other switches to fit

and at back of switch selector it still uses prongs & copper plate on selector plate

plus it is re-enforced so need to mod box to fit 13:1's in their v2 boxes

(on v3's they go straight in coz not re-enforced - but a few v2 boxes are like this)

 

but they are a good strong cheapo box that won't crack easily like a G&G blow back box

& way more reliable than say a Nuprol or others with micro switches that burn out asap

 

I suppose the 516 is like a half decent Punto

cheap as fuck, you know it ain't high end to challenge an BMW

but if you go easy it will do ya proud to run around with

and if it really goes tits up then you cut ya loses and buy something else a bit better

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3 hours ago, Sitting Duck said:

Now don't get me wrong, fancy high end shit is all well & good

if you got money falling out of your arse & all that

and some Youtuber's build hose machines almost as big as their fucking ego

 

and yes ultra high parts are manufactured to higher tolerances blah blah blah

and a CNC box owner will obviously say it is the best

(fucking hope so for the money you paid for it)

 

But there is also the classic newbie mistake of slinging in the most expensive parts

without checking how they all fit & operate together

(if you ain't checking = you ain't teching)

 

100% this

 

the real skill in teching is getting a good gun to shoot well on "inferior" (put a lot of weight on those quotation marks) parts.

 

unfortunately some folk make the mistake of thinking that more expensive parts=better parts when the reality is even a well-made high quality part can absolutely ruin a gun if it's not the right part for that build. for example that gearbox shell might be superbely made and exactly to spec but if that spec isn't exactly the same as the reciever it's going into then the hop might not line up, the body pins might not line up just right or the motor alignment might go out but only when you tighten down the stock screw or something along those lines.

 

i mean it's entirely possible to have a £2k+ gun be incapable of hitting the broad side of a barn if it's not setup correctly.

 

 

 

as an answer to the compression problem personally i'm a big fan of these nozzles:

https://www.ak2m4.co.uk/internal-parts/nozzles/ec-m4-metal-nozzle-double-oring-21mm

 

although they're out of stock at the minute.

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  • 3 weeks later...

well she is finaly finished seems to be running sweet dry firing anyway just bout to test it with some rounds

 

 

she has also cost me my 2ndry screen on my pc well more myself has put the spring in the wrong way it bound got it apart but as i did it shot through grip and hit my 2nd screen lol thank god wasnt my gaming scree lol

 

 

20210222_230858.jpg

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the 621 saga continuesok so testing today has shown that the safety latch is pretty much screwed cant use safety at all regardless of what trigger,also in semi it will shoot a few semi shots then ahoot again and get a  burst that continues for a second after i have removed my finger if switch to full auto it does auto but continues for a second or so after removing finger from trigger i did upgrade the tappet spring to a gaurder one but doubt thats causing the issue   @Sitting Duck what you reckon sorry to be a pest again bud

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thats also on both 7.4's and 11.1s

 

thinking of reversing steps try the original motor with the gear set then if needs be revert bk to standard gears and just buy a standard set for my step son

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sounds like trigger sticking? possibly mixed in with the cutoff jammed.

 

over-run is a thing but never heard of a gun over-running by more than 1 round.

 

the safety is an easier one to diagnose as the lever is very visible in it's function when you split the box- easy enough to see if it's bent/binding/jamming on the trigger itself.

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will take apart and give the sensors a clean incase any grease flicked offf onto them when i was test firing as trigger itself isnt sticking or binding is nice and free moving

 

the safety i think is more when its screwd together when the box is together thinkthe screw is pulling through the threads so think ill need to replace that to sort that issue

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haha yeah i upgraded to the perun bud :),did tag him so just waiting on his response see what he susggests aswell before i end up putting the gun to a tech next week lol

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ahh, optical. this might explain things, they can be quite the bear to work with.

 

i've generally preferred external although admittedly i may have sneaked a titan into the akm recently because i didn't like not having precocking that first round after firing auto (and yes i really did buy a titan just to make that small change)

 

tbh at this point you're talking things like calibration etc (assuming no grease on the sensors as you're planning to check), sadly i'm no help as i've never used perun's stuff.

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only calibration u can really do with the perun v2 is trigger response bud,ill strip her down give the sensors a clean see if anything maybe one of the wires is cover a sensor slightly will check all that :)

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13 minutes ago, miserydrift said:

only calibration u can really do with the perun v2 is trigger response bud,ill strip her down give the sensors a clean see if anything maybe one of the wires is cover a sensor slightly will check all that :)

 

could be, maybe the trigger is set too sensitive and it's sometimes not resetting enough to disengage?

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ok steps tried sp far cleaned sensors,changed internals back to standard bar mosfet,changed the stickers on the selector plate yet it still continues to happen gah

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OK regarding safety...

 

Did you remove the copper plate on the selector plate when affixing sticker for sensor ???

 

364469014_Screenshotfrom2021-02-2406-54-20.thumb.png.51f8eedebdc56b96ef7ae1dc4f3c73b5.png

 

What "might" be taking place is the safety cam, (looking like a bloke with a big nose)

the cam or arm is not being pushed back to 12 o'clock when inside the receiver

Safety very likely all works fine on the bench with grip/motor

but when you install it the selector plate is not pushing the safety cam/arm to exactly 12 o'clock

but just a whisker shy say 12:15 ~ 12:30 (taking the safety arm as the little hour hand)

It is a whisker shy of 100% 12 o'clock and the way shit works the actual safety stop is just below trigger's stop

and this just slips under the limit stop of trigger and fires on SAFE

 

Now if you removed the copper plate you likely lost near 1mm of travel pushing safety arm into position

 

If you kept the copper tab - then it "should" still operate correctly, hence when had issues with new trigger

I said use old one - which seemed to help

 

Anyway....

 

What you might need to do is add a small whisker of material on the left side of selector plate tab

if you have removed the copper plate, then perhaps super glue a capillary straw/pipe like WD40 tube

to left side of selector tab & test - you just want something 1~2mm max glued on to test

(if it works then add a bit of epoxy or glue it properly onto the selector plate)

Basically anything to increase the travel slightly on SAFE so safety arm rises a whisker more to engage it a

 

If you have the copper plate still on the selector plate, then just add a little line or drizzle of solder to left side

I broke the cm.515 selector getting in/out a few times & used a cheapo one lying around

unfortunately the same thing happened, on safe the gun was very like yours, mostly still able to fire

I drizzled a slither of solder onto the left side of copper plate and the arm then raised fully to stop the trigger

 

If you haven't removed the copper plate then it doesn't make sense why it isn't working correctly as it was

and you must check the arm itself is not fouling on the Perun inside the box - shouldn't be but check just in case

if it isn't fouling, then chances are for a bit of wear & tear or other reason the selector is not pushing the safety cam

quite enough to the left safe position to ensure the arm itself rises fully

 

(the oem cheapo orange v2 selector plate I used was made ever so slightly different, the arch was cut a smide over

and so the TM compatible bollox - even with the copper plate fitted, failed to raise the safety 101% correctly like before

a slighter of solder, sticking to the copper plate like shit to a blanket did the trick

or glue a piece of material (plastic strip or say outer insulation sleeve from old wire bit of thin wire)

 

Now the sporadic firing problem is likely to do with the different sector gear...

It is possible the the optical sensor is not picking all the teeth on the 13:1 sector

be it being jet black, chunkier teeth or just needs to unit shifted a fine minor smidge one way

 

could be grease on senor, sector rubbing, to do with light not picking up all the teeth

(so cycles another once or twice coz it only read say 14 teeth not 16 if full sector gear)

 

Also with optical units the gun can be made to cycle if light enters the box

often people go to test a box with box & grip/motor & light enters that tiny pin by trigger

and can make some optical units go nutz & confused & calibration difficult

 

even then if hold gun upside down towards sun on a sunny day

or shine a bight light at trigger, the light can enter box and cause gun to fire all by itself

yes - optical units can be prone to the odd issues of the sensors incorrectly detecting stuff

 

I doubt if the colour of the sector really makes much difference, it works by the teeth breaking the beam 16

or whatever it calibrates the gun/sector as...

So most likely the different sector is ever so slightly different, a whisker out of wack picking up varying teeth

so likely need to loosen unit, shift it to right/left slightly & retest if all teeth detect properly

 

One thing to try is pull the trigger only what it is needed - don't pull it ALLLLLL the way, just enough to fire

as the Perun on ultra full trigger pull can fire, but trigger goes beyond the range of sensor(s) so think trigger is reset

when in fact it has travelled too far on max pull, so that when you release it, it comes back across the sensors

and thinks it is another pull when in fact it is resetting to rest - so gun gets very confused & fires sporadically

 

on the 516 box there is a casting where you can easily add material to limit the final trigger pull

alas on the 621 box it is not reinforced and doesn't have this material to easily half trigger travel

so alternative method or proper adjustable speed trigger/mod might be needed

 

but before you do owt shiting unit about, test on half trigger pulls if gun is sporadic (trigger sensor issue)

or if no joy then likely shift unit about to improved the sector sensor detection issue

 

hope some of this helps

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i sorted the safety bud changed the screw and safety works fine now

 

im contemplating just putting it into a tech now tbh starting to lose paitence with it and will end up throwing it against a wall soon haha

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Well the other alternative is go back to std 18:1 in 621 & RA motor (still quicker)

but to use 13:1 in 516 you need to mod the arc bit on top half of reinforced 516 box

then the 13:1 spur will fit & spin ok

 

use SHS/RA motor in 621 with 18:1's hoping the Perun will work OK again

then the Cyma motor in 516, with 13:1 after modding arc

 

both guns will perform "roughly" about the same say 16~17rps on 7.4v lipo sorta thing

bit of fucking about no matter what...

 

should have just bought your son a set of 16:1's that would go straight in

and you could have left the 621 alone and just used the RA motor in it or kept as is

 

I blame the kids in the end - Daaaaaaaad - it's not working/fucked

 

"Well it was running alright when I left it"

 

bloody kids - cost you a fortune they do

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