Well Hello There :

[Misery]

as the per the title hello new to airsoft literally managed to pick myself of a steal of a deal on 2 2nd hand cyma's for me and my step son to start using as soon as the rona buggers off! will be using the cm.621 for myself and let the boy use the cm516,came with 3 hicap mags 6 mids 2 stick 3s lipo's for the 621 and 3 crane nihms for the 516 both guns have come with a red/green dot sight,loads of bbs,a excortek chrono a vest gun bag and few other extra's

View attachment 67646

View attachment 67645

View attachment 67647

View attachment 67648

View attachment 67649

 

[EDcase]

Nice one.

Here's to the end of covid

 

[GAMBLE]

Hi @miserydrift! ?

Welcome to the forum, Good luck getting started, when it’s safe! ??

?GAMBLE?

 

[Misery]

thanks guys well we have a problem so far 5 rounds in and the piston has crapped itself on the 621 lol oh well order up a new one next week any recomendations on a piston lol

 

[Jedi_Master]

Welcome .

 

[Misery]

thank you

 

[Sitting Duck]

Well I was gonna post Obi dropping down to say Hello there

to respond & drop into this thread...

but for Wu-Flu stuff this came along instead...

Greetings anyway - good budget starters btw

A SHS piston is one of the best all round pistons

BUT they can be a bit tight in numerous boxes

& "bind" or stick/snag as they retract, often binding especially near back of box

Generally SHS pistons & gear sets can be a bit chunky, robust but chunky

or tight fit in some boxes - not a massive biggy but might need a bit of work/modding

or more planning in some boxes

(in G&G boxes, they have a bit more room & SHS pistons do not bind)

In Cyma/JG boxes I have found SHS pistons bind a little

SHS pistons - if you go for one

just go for the std blue full metal rack one

avoid the lightened ones and forget the 3 or 7 steel teeth ones

as the plastic teeth on those are like DairyLea

For hassle free stuff - go for the Cyma metal piston...

https://www.ak2m4.co.uk/internal-parts/pistons/cyma-15-tooth-reinforced-piston

that'll go in no problem

You'll need to swap over the piston head AND the alloy spacer

or buy the complete version...

https://www.ak2m4.co.uk/internal-parts/pistons/cyma-15-tooth-reinforced-piston-piston-head

I'd also buy an o-ring or two as Cyma o-ring is meehhhhhh

change o-ring and the compression really improves

another thing is the loose as f**k cylinder head

yes you can use ptfe tape bodge, but wrap it carefully & trim excess with scalpel

you will need about about 7 wraps or maybe 8 - I shit you not

it is a very loose cylinder head

older models were white piston/cylinder head & clear tappet plate

new models are now blue bits - but still loose as f**k cylinder head

BUT still works with ptfe bodge - just quite a bit/lot required

yes you could change more - but I'd avoid changing too much

as it is your first go at things - so change only what you really need to

why did piston fail - be careful about pushing the gun on 11.1v on a faster motor

if you go too fast above 20~25rps then you can hit PME

not a big problem on plastic piston - it will break first as weak point

But on full metal rack, then no weak point so gears & metal rack will go crunch

(more mess if PME takes place)

Hopefully the plastic piston just failed, but Cyma stuff

the Cyma plastic piston - like JG std plastic pistons are fairly robust

unless you was extremely unlucky or took the piss

the box is quick change spring - so that will help or assist in a straight forward repair

(less likely of bits exploding as you open a std no QC gearbox for first time)

best of luck - just replace the bits, new o-ring too, bit of grease etc.. SORTED 

 

[Misery]

thank you will get the full piston ordered next week ,as for why it failed i couldnt say i fired around 5 rounds through on semi then got the dreaded chewed plastic sound so instantly stopped then stripped down,yeah have been watching alot of negative airsofts vids so decided to crack the gearbox open and take a look myself quite gd with my hands work on motorbikes in my spare time,the gears all look perfect its literally just the piston thats went on it luckily.thank you for the links and help greatly appreciated

 

[Sitting Duck]

Could be a genuine failure - the piston head loose (unlikely)

rubber pad on cylinder head came adrift (unlikely, but a possible)

could be a jammed BB - this will plug the compression and slow piston return

tbh - think this is a bit unlikely as Cyma compression as std is not 101% awesome

o-ring is meeehhh, cylinder head loose as fuck

so not mega insane compression building asap stopping the piston's return like on an awesome setup

if s/hand the previous owner could have caned it and risked PME

then you got unlucky when you picked it up to put some rounds through it

not a massive biggy - it could do with a minor tweak but don't go too nutz

it's pretty decent and still a £100 gun no matter what shit you chuck in there

just change what you need to

improve the meehhh compression - bit of grease and get it going again

ptfe will work - but you will need quite a bit of it

normally only say 3 wraps - but about 7 on really loose Cyma heads

yes you could change cylinder head, but then some cylinder heads are tighter looser "spouts"

for certain nozzles etc...

Yes you can change nozzles too - but an SHS red M4 nozzle sits very loosely on a Cyma tappet plate

and Cyma tappet has cut outs coz it is reinforced inside

Sooo to use a Red SHS Nozzle you need a SHS tappet plate & then modded like a Cyma/Lonex tappet

with the cut outs up front...

See how something "so simple" becomes more & more involved ???

hence sometimes it is wiser to change as little as possible

to avoid creating a new issue (or two) for every "improvement" you attempt

hence perhaps keep it fairly straight forward for your first attempt

as these Cyma's are a tiny bit qwirky - still amazing value

just a few things you need to be aware of before chucking money into them

most stuff works - but a few things can be qwirky and minor mod/work required

plus you change more & more without checking stuff you can create issues

or make matters worse if you are not careful

At times it is very wise to keep things somewhat simple

(especially with cheap chinese sweat sweat shop toy guns assembled by a 5 yr old)

 

[Misery]

ach one of the joys of taken a pre owned gun i suppose

taken all on board bud will replace the piston and go from there when something else breaks thank you

very true you can only polish a turd so far i suppose lol

 

[Sitting Duck]

Cyma's are not turds though (honest)

yes they still make low power turds

but the 5xx series & the slightly better 6xx series really upped the game for others

they are slung together - but they really are pretty decent starters

their v3 AK's have much respect etc... even by the high end players

their M4's are also very good value - just a tiny little bit qwirky in some areas

but all or nearly all gun manufacturers can be a tiny bit qwirky on some models

some shit works no problem but there is always the TM compatible myth

in fact it is really TM Compatible-ish as often most builds/upgrades need a minor tweak/mod

just don't go too nutz and make more work/problems than you need

until you gain a bit of experience with these Chinese sweat shop toy guns etc...

 

[Brophy]

Welcome to the forum, nice one on getting a hold of some guns to tinker with in the meantime

 

[Jaylordofwaargh]

@Sitting Duck beat me to it but

Kenobi! 

Well worth adding

Welcome