Cyma Cm.621 Upgrades

[Sitting Duck]

Oh leave off - I'm still trying to figure that out myself

 

[Adolf Hamster]

Oh leave off - I'm still trying to figure that out myself

i know what you mean though, it's impossible to make the complete guide for everything because every part and every gun is subtly different, things change over different batches etc etc.

 

[Davegolf]

@Adolf Hamster no need, @Sitting Duck writes the guide every time he posts ?

I love how every time the ‘I want to put a new spring in’ spirals into full blown custom box

 

[Sitting Duck]

Can't accuse me of composing very brief & vague posts

just bored shitless & very very very sad

 

[Misery]

Thanks guys and yes it seems it was a jam thats caused it now to order the piston sitting duck mentioned and go from there,so hard not to strip the 516 for its piston but after chrono'ing it earlier i think i will leave that gun alone as its sitting around the 315fps and acurate as hell as managed to keep my groupings quite close now to get the 621 to be the same lol

 

[Adolf Hamster]

Congrats, you've managed to miss the pitfall far to many people (myself included) fall into- not fucking with a good fun unless you have a backup

 

[Misery]

haha yeah learnt my lessons with that when i use to race motocorss as a kid plus i have time to get rhe 621 sorted with this lockdown so if i leave the 516 i can still shoot targets atleast

 

[Tackle]

Congrats, you've managed to miss the pitfall far to many people (myself included) fall into- not fucking with a good fun unless you have a backup

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

View attachment 67696

 

[Misery]

some people just like to tinker im one of those usualy but with this hobby i think ill wait a while to tinker around more lol

 

[Misery]

@Sitting Duck im actualy doubting it was the hop that caused the jam now,was running a mag through the 516 on semi  trying to get the sights tuned and boom jam took mag out and relised i was using a hi cap mag cleared the jam  and gun is fine thankfully arse puckering moment lol

 

[Adolf Hamster]

some people just like to tinker im one of those usualy but with this hobby i think ill wait a while to tinker around more lol

good luck with that.

if you're anything like me you'll never shoot the same gun twice.....

 

[Misery]

haha with how expensive this hobby is i will have to wait having the amount of kids i have hampers my spending ability lol

 

[Davegolf]

I guy at a site I play has his kids there, they are damn good and easy to hide!!

 

[Misery]

I guy at a site I play has his kids there, they are damn good and easy to hide!!

haha id love to bring all mine but 4 have aditional needs and 2 ones to young and other is coming with me

 

[Sitting Duck]

Glad you got stuff ordered to help with ya 621...

I could have suggested the "compression kit" Pete @ak2m4 does...

https://www.ak2m4.co.uk/m4-compression-upgrade-kit

Which offers great value at say £5 each piston, piston head, nozzle, cylinder, cylinder head

However not sure the ZCI piston binds a bit like SHS in some boxes

(Cyma certainly wont)

The SHS/RA nozzle is loose on the qwirky Cyma tappet plate - well SHS is for certain

Cylinder head would be nice but 7 wraps of ptfe will improve the shit loose std one

Cylinder - well the Cyma ones are usually a decent silvery type with port suited for gun already

(crappy brass cylinders are OK, but snappy guns they tend to warm up a bit

if people start to polish these brass ones a bit inside you can feel how quick they warm up)

Piston head - well if you put on a better o-ring that is usually all it will need (after ptfe cyl hd)

and like I said sometimes you change more bits you can run into issues

(especially on the slightly qwirky Cyma v2 boxes)

So just replace & service what you need to get ya going again

With regards to jamming - could be number of things

decent bb's really make a difference, G&G's though expensive are a good brand sold by many places

cheap eggy ones with seems & variations in manufacturing result in all sorts of issues

even weight fluctuations on cheap batches = bigger fluctuations at chrono too

G&G is just a well known, easily available brand at many shops/sites

some rate Geoffs or Blasters - just use something "decent" if you can

You could be trying to hop stuff too much, trying to lift .25's on some shit bucking

winding the hop on more & more on a hard/crappy bucking until it just cloggs

an old stiff bucking struggles to control finely the backspin/lift on certain BB's

like tight bucking lips - the BB is wedged either under nub

or in case of tight bucking lips the BB is stuck just outside the bucking

both will clog up the flow of compression & risk PME

The trick is to NOT KEEP FIRING - especially on Auto

remove mag, fire a few shots on semi - if no joy

then likely use jamming rod etc...

misfeeding - actual MISS feeding is another issue that "usually" doesn't jam

ergh it misfeeds - though a jam will cause other rounds to misfeed of course

different mags can feed better/worse

sometimes they can pull/push hop unit slightly which can effect the nozzle clearance

to chamber a BB up feed tube into hop unit & through lips into position under nub

People think mid-caps MUST feed better than a high cap

not always the case, some midcaps the bb's can snag inside the mag's long snakey spring

that pushes up 120 or so bb's without winding - trust me some mid caps are shit for jamming

(sometimes at anytime, usually as the follower turns tightly in one of the bends inside mag)

A good high cap should feed say 20~25 BB's without winding (once fully wound)

don't leave a high cap wound or spring tension goes shit & only feeds say a dozen bb's or less

You may find that some guns like a certain mag - this is not uncommon

your 621 might be more picky than the other M4 and one or two mags work better/worse

Feed issues can be tricky to diagnose (especially via forum text)

so experiment and diagnose through a process of elimination to reduce potential jams in each gun

sometimes you can fit a delay clip to assist feeding/chambering of bb's

but on Cyma gears - there is a bigger cam on sector that most delay clips won't fit on

so looking at changing gear/sector to fit a delay clip to improve nozzle/tappet retraction...

naahh - not yet perhaps

(something to look at at a much later date down the line - just get gun working again)

Jams could likely be hop on too much with an old stiff shit bucking

and/or shit bb's in a dirty barrel, which the 6xx series is supposed to a tighter barrel

so give barrels a good clean too and use decent bb's

Tight Bore Barrels need to be kept clean and any minor irregular shaped bb will not glide down it

Got a 600mm shitty MadBull TBB barrel that is tighter than a nun's whatsit

and very few bb's can drop through that easily without snagging - way too long and too tight

So shit like 6.01's are just too tight - especially in longer barrels

6.03 barrels are about as tight most people generally use with quality BB's

(but still need a bit of reg cleaning)

Try different stuff, on say 7.4v LiPo to establish what BB's & mag work best for each gun

then go a bit nutz once you know it feeds reliably etc...

They're s/hand guns (I think), so expect the odd niggle

heck we still get minor niggles with new guns, like new cars/bikes etc...

You'll suss it all out in the end I'm sure for trouble free peew peew peew

 

[Misery]

Havent ordered yet just got em sat in basket till payday

so would you say im better to get the compression kit youve linked or just a new piston and o ring set?

yeah have taken it all on board tbh i should of known to do it that way had a chinese supermoto for getting to a to b thing was a proper work horse and would only feck up if i *upgraded* crap on it lol the next part down the line would fail etc

will get some decent bb's added to one of the carts

yeah i think once its sorted ill go through all 9 mags and see which runs better in her

i hadnt touched the hop so was set to what ever my friend had it set to for .25's i have changed the hop rubber and nub to the red nub and macaron rubber this morning and set the hop to zero so when i get the replacemtn parts thats all gd to go also cleaned barrel on both guns,just wondering would it be worthwhile doing same hop rubber and nub upgrade on the 516?

ill have to order a couple 7.4's in and need to dig out my decent rc intelicharger as not a fan of the ags one i have here

oh totaly and thats part of the attraction to me as i can get my head into em andsee how they work etc where as if they work perfectly i wont bugger with em so would never learn much

thank you again bud you and everyone elses help has been greatly appreciated so far

 

[Sitting Duck]

Well as explained (briefly - *sarcasm)

the KIT offers excellent value - nuff said

but as explained the nozzle may wobble

the piston "might" bind (it might not)

the cylinder only available in full or half type

(as said you got the correct cylinder in there about 3/4

though at times the type in fractions or type A-B-C-D is a bit vague

I prefer to measure the distance of port to front say 43mm)

The piston head is alloy - but a good type for compression

yet some prefer lighter and possible less risk of scratching POM piston head

(I've always said give same gun to say 10 techs and they will all have their preferences

of what to change, what keep etc... how far to take stuff on what budget etc...)

waffling again

The kit offers very good value - don't think anybody can deny that

(price it up separately & see for yourself)

The issue is one or two components might not be best suited as is for the Cyma v2

(nozzle is one example, it might fit OK but RA is oem SHS so reckon it will be a little loose)

Don't get me wrong - you could buy just the basic Cyma piston & new o-ring

AND the KIT for a future gun or if the other gun went tits up

and you was fine doing some minor checking/minor modding to ensure it went together OK

I'm just pointing out the options and the value in the kit

(get full cylinder perhaps & you can make it ported if you wished to your spec)

I'm not saying deffo get the kit - I don't know what your budget of toy gun shit is

(especially in January after Chrimbo cleared you out)

If funds are tight just get the piston & o-ring

if you're OK or had money to splash then get kit as well PERHAPS

Now at risk of pissing Pete off - he's gonna fucking kill me

you could ask Pete via pm/facebook or whatever to measure the piston

between the rails to check dimensions and see if it is much thicker than Cyma

or a bit thinner than SHS pistons that often bind in some boxes

(that way you might know if it will bind or just need a light sand to glide smoothly)

it's not just between the rails, but the rails themselves how much they protrude

but some pistons bind a bit & some bind a lot that effects its efficiency (even risks PME)

SHS pistons I have are 19mm between rails

(a smidge under/over at either end)

Cyma metal rack pistons are say 18.15mm aprox

with the pinky ones being 18.4mm to 18.55mm say

(so as said they sit inbetween SHS & Cyma pistons)

I dunno what Pete's XT or even ZCI pistons are

but highlighting why some pistons bind in some boxes etc...

The XT piston could be fine, not as fat as bindy SHS

I really don't know - but SHS can bind in Cyma/JG's

and Cyma pistons can be a little wobbly in say a G&G box for my liking

as said this "Tokyo Marui Compatible" is more like compatible-ish at the best of times

View attachment 67729

yeah might need a "slight" mod there m8

I mean for starters to see if I'm talking out my arse a sec

you can grab some plumber's ptfe tape

wrap around 7 wraps around the cylinder head and retest to check seal

(it is a BODGE, but does work if done neatly - trim off excess with scalpel etc...)

the o-ring, you can remove and wrap it around the outside of cylinder to stretch it

(some warm the rubber, some leave it on cylinder for weekend/week to naturally stretch a little)

but a new better fitting o-ring is best as the Cyma one is a bit small to begin with

do that crap - test compression, see if it improves for next to nothing

heck you can test for leaks at cylinder head in a bowl/sink of water looking for puncture

(nozzles will never seal 101% as they gotta move freely so will blow slightly under pressure

even with an o-ring or double o-ring or they struggle to glide free & smoothly)

see if that improves compression

but you will need a new or stretched o-ring at least to check compression

(coz the std one is a bit shit)

and the cylinder head OMG Cyma it is as loose as fuck - plenty ptfe required

but can do the trick on budget without buying numerous bits that you don't REALLY need to

(Just Cyma - the fucking head is a bit too loose compared to some makes)

You can get by with mostly stock stuff and get these to sing quite well

(like Luke at NA does so often)

I've covered the extra work regarding SHS nozzle & tappet plate in Cyma's

I normally use plastic cylinder heads if I can get them to seal well

others will replace with alloy head etc...

then some nozzles are a too tight fit on some spouts or vice versa

so then I might change stuff around or go to plan B etc...

again waffling & over thinking shit, but I got a box of bits n bobs spares to swap shit around

I'm giving you the heads up, what options there are and offering you the simple straight forward approach

plus mindful of not buying more stuff than is really necessary to get it going too

As said, not wishing to piss Pete off (much)

but say if he popped the XT piston in say a JG v3, Cyma v3 if he hasn't a Cyma v2 shell to hand

(that's another fucking annoying thing about Cyma v2's, they got a smaller cylinder window

that a bare piston won't fit through on its own like most v2's to test if a piston might bind)

if the piston doesn't bind in a JG/Cyma v3 box then chances are it "shouldn't" bind in Cyma v2

if that be the case you could buy the kit and use most of it - nozzle might not wobble (but think it might)

but use most bits - though get a couple of o-rings - one for the other gun at some point

As for the other gun - if it shoots OK then LEAVE IT ALONE

you could swap barrel/hop/bucking combo over to test/try if they are similar length

but I'd avoid stripping down both or fucking around too much - always leave one gun working

(plus if it ain't broke (or not too bad) then don't try to fix it)

 

[Davegolf]

Pretty much all parts are 'compatible', but what really makes everything work properly is awareness of the fit and range of motion of things.

To that end a great gearbox is ultimately the sum total of being aware, observant and having patience - all of which are free.

Other than that some measuring combined with a file and sand/emery paper will make everything compatible.

Sealing of things with PTFE tape works for cheap if you have limited parts.

 

[Misery]

aahhh i get ya bud wasnt sure if u were recomending that over the standard piston

ill get both and see how the fit is etc if theres any issues then i have the standard version to whackor send off to negative and have him fit it ? in as at min i have a budget of around 100 for parts and 100 for to sort out protecion clothing and boots.as i was originaly planning on spending 300 on a new gun when i managed to pick up the bundle i got,i am thinking of buying a warfet and doing plug and play on the 516 till i build my dmr*way off in the future* and then swap it over to the new build in theory lol

yeah i think im going to try keep as standard as possible other than the hop upgrade ive done rubber wise as before it did crap itself i managed 2 chrono shots and was only hitting 215 but if the compression wasnt there that wouldnt help would it?

nah not waffling at all man your insight is extremely useful!and im defo going the straightforward route why over complicate it for myself than i already am lol

yeah true your right will wait till it breaks to change anything lol

 

[Sitting Duck]

The 516 won't be a Quick Change spring

so opening it up requires a tiny bit more care due to spring still inside

as said you could swap barrel/hop combo around as they seem similar lengths of about 300-ish

to check if messed up & focus on one gun than screw two guns up at once

Warfet ain't cheap on 516 £70 gun

it's up to owner but a basic mosfet will suffice

and even then a schottky diode will reduce sparks at trigger contacts

deans connectors are probably worth a go £ for £ if you can solder

but this crap is for another day

get one gun sorted first then with wisdom/experience look at any issues/upgrades on other perhaps

again - remember even with a £150 Titan it is still a £70 Starter