Cyma CM.041J Blue Edition low FPS issue

[matas17]

So I had this MP5 for a while now, installed following:

Gate Titan

SHS 13:1 gears
steel tooth piston

new piston head

3/4 cylinder

double oring cylinder head

and 20.4mm oring air nozzle (same length as original one)

My issue comes to the point where it fires fire and bbs fly out of a barrel but FPS is extremely low aprox=120-140 with m90 spring and 100% airseal. I am at the point where i cant think of anything else that could cause this. I tried flipping delay chip, trying out different air nozzle, gears, bucking/barrel, etc.

I am about to give up on this AEG as i cant figure out what could cause such low fps.

 

[Zarrin]

There can be any number of issues but lets try and exclude a couple...

- Have you tested for compression / air seal on the cylinder set?

- The air seal nozzles with o-rings can some times be a bit too tight on the cylinder head, resulting in the nozzle firing forward in the hop unit too slow. This can cause low fps. Have a look and see how tight the nozzle is on there by testing how easily the nozzle can be pulled up and down the cylinder head - if its fairly stiff, then this could be your problem. Maybe swap out and test with a standard type. You say you tried some others.. maybe try the og one.

- equally an old weak tappet spring can cause a similar problem, and in combo with a tight air nozzle could be even worse.

- is there a slight bend or misalignment of the nozzle perhaps causing it to rub against the inside of the hop unit?

- is the nozzle sitting reliably and firmly inside the tappet plate groove?

- Is the fps equally low with the hop fully turned off? - test

- A hard grade hop rubber can sometimes really hold quite a grip on the BB in the feed lips and the nub itself causing issues - maybe swap your rubber out for a decent soft 50/60 degree sleeve - prommy purple are usually pretty good. 

- A bad barrel, hop unit, hop rubber combo match up can cause pretty bad air loss - try swapping them out one by one but before that maybe try the same setup with some plumbers tape round the base of the hop rubber sealing it onto the barrel, that's given me massive boosts on certain builds.

 

[Asomodai]

Are you using mid cap mags? You might have midcap syndrome if you are using full midcaps. Use a half filled Midcap and test your FPS. 

 

[matas17]

There can be any number of issues but lets try and exclude a couple...

- Have you tested for compression/ air seal on the cylinder set?

- The air seal nozzles with o-rings can some times be a bit too tight on the cylinder head, resulting in the nozzle firing forward in the hop unit too slow. This can cause low fps. Have a look and see how tight the nozzle is on there by testing how easily the nozzle can be pulled up and down the cylinder head - if its fairly stiff, then this could be your problem. Maybe swap out and test with a standard type. You say you tried some others.. maybe try the og one.

- equally an old weak tappet spring can cause a similar problem, and in combo with a tight air nozzle could be even worse.

- Is the fps equally low with the hop fully turned off? - test

- A hard grade hop rubber can sometimes really hold quite a grip on the BB in the feed lips and the nub itself causing issues - maybe swap your rubber out for a decent 50 degree sleeve - prommy purple are always pretty decent. 

- A bad barrel, hop unit, hop rubber combo match up can cause pretty bad air loss - try swapping them out one by one but before that maybe try the same setup with some plumbers tape round the base of the hop rubber sealing it onto the barrel, that's given me massive boosts on certain builds.

Click to shrink...

- I have tested compression several times with air nozzle on and off and i could not push piston past the cylinder ports
- I have checked the air nozzle and it moves easily up and down the cylinder also tried different air nozzle with no issues moving it.

- Tappet plate spring is brand new as i bought them to replace original one.

- i check FPS with hop off and hop on with same issue, I also replaced Cyma hop unit with G&g mp5 hop unit but had same issue with low fps.

- Current hop rubber inside the aeg is Maple leaf decepticon 60 yellow, as i had no issues with them before so i used the same again.

- At the moment i have Madbull 6.03 247mm tight bore in it and i tried ZCI 6.02 300mm tight bore and had same issue, and i tied the plumbers tape and it didnt go up in fps

 

[Lozart]

@Sitting Duck will probably be better equipped to answer this but I think you may have too weak a spring for the gear ratio you're using. 

 

[Sitting Duck]

It "sounds" like hop issue to me but I don't own one

A quick test to do first:

with box & hop out...

when the nozzle is fully forward 101%

place hop unit up against the box...

you should "feel" the nozzle starting to seal against the bucking lips

with still say a bit more to go before the hop rests 101% against the front of box

then in normal operation the nozzle "should" be sealing properly

If the above test is all OK then it could be a nozzle/tappet issue

(the tappet is catching, not returning 101% in use)

Or try std nozzle, sand tappet front a little

but sounds like the nozzle is never sealing against bucking properly

like the lips are way short of sealing with nozzle and air is pissing out

or nozzle used is not sliding/aligned with hop correctly

like a fat nozzle that is tight fit or catching against the hop and stopping it sealing

(some nozzles - the "shoulder" can be too wide/fat on some hops & catch or drag in operation

eg: some brand new G&G M4 hops are a bit of pinch with a SHS M4 nozzle & risk snagging)

Your fps is way way way low

you gotta test that the nozzle does seal against the bucking lips

get them out - mate them up and see if you feel a bit of resistance from bucking lips

they should just start to touch and you should have near 1mm gap from box say

so when the hop is mated up properly there is a good seal of nozzle to bucking lips

If that works out OK, next thing is to grow another pair of hands....

plop a bb into hop/barrel, mate it all up and chrono a few times...

might take a few attempts to get it to fire a bb through chrono etc....

but hopefully you get a shot or two off through chrono....

if that says 300fps instead of 150fps or whatever you are getting

then issue is the assembly of hop to box

or the hop being shifted away from box when mag is inserted

like it can happen on M4's if no spring or stuff pressing hop back towards box

It "sounds" like bucking is way away from nozzle and think it "might" be poor alignment

or tight fit nozzle or hop shifting forwards never letting nozzle seal properly

(be it mag shifting it forwards or some other weird shit)

break it down - the box & hop

break down the problem testing them with 3 hands that they do kinda seal OK & chrono

if that checks out then it is an alignment or fitting issue in gun - quite possible

if you can feel it sealing with you holding the hop/box together

then the bucking is not fitted correctly or needs investigating or nozzle/tappet issue

(might have to go back to stock bits n bobs to get it working again & go from there)

it is a process of elimination in most cases, often shit goes out of whack with more new parts

but I'm tending to think if parts are compatible then something in the box/hop alignment has gone out of whack

you got a m95 spring delayer 13:1 etc....

what battery you using and what motor - in other words what rps ???

I mean you got a delayer on it but what sort type ???

I doubt if tappet timing is an issue unless you are using a massive delayer & enormous fin

but depending on tests...

another area to consider is

the chunky SHS sector with a chunky axle could be impeding the tappet returning 101%

so the nozzle does not return fully coz the tappet fin is stopped by chunky axle on sector

gimme a sec...

pic says 1,000 words - see the sector axle & fin

needed a bit of modding to prevent the tappet being stopped short on sector axle...

now this mod was coz I sanded the thick front of SHS tappet, but it can risk catching a bit anyway

(ahh the good ol' TM compatible bollox), when you start changing stuff

The friggin' attention details on EVERY f**king part you change should NEVER be taken for granted

coz this TM compatible BS means next to nothing - some shit works but often it don't just drop in

many bits need checking and often a bit of sanding or tweak to ensure it works 101% as it should

your nozzle "might" be risk being restricted by the fin stopping short on a chunky SHS sector

BUT I don't know for certain in your case but it CAN happen in some builds

(and SHS gears are quite chunky)

Or - you could have the fin snagging on chunky shims on a low sector

that a big diameter shim on top of sector starts to catch the fin at times in operation

(it is rare but I always save smaller external diameter shims for top of sector)

than use big fat diameter shims on top of sector....

or at least use smaller shims first on sector and a fatty shim last

(you get the idea - watch out for potential fin snagging on sector axle/shims)

but there are loads of things it "could" be

a bit more info, a few tests an a pic or two could help, but a few ideas to try

hope some of this crap helps

PS - soz for overload/long post - but do the hand hop/box test first

before you start stripping down stuff I suggest

It is going to be something really really stupid & silly

so don't go ultra nutz tearing things apart

though maybe consider some of the crap and check EVERYTHING & EVERYWHERE

when you starting changing & altering things in future builds to reduce potential headaches

(if shit can go wrong then Murphy's Law says it will regarding TM Compatible crap)

 

[Sitting Duck]

Hold up !!!!

this is an ongoing issue is it not ???







Now it "seems" that the cyma MP5 nozzle is a 21.4 ish nozzle...

https://www.airsoftforum.com/topic/241139-massive-air-seal-nozzle-leakeage-on-a-cyma-mp5sd/

so it seems 21.4 to 21.5 ish is required...

(also heard a Galaxy MP5k nozzle likes a SHS M4 too

but the "shoulder" of red SHS M4 is too fat so needs modding to nozzle shoulder

or modding/widen the Galaxy hop entry so chubby nozzle can operate smoothly)

in other words not all MP5 nozzles are the usual MP5 length

(different guns makes/hops work with different nozzle lengths than 1 size fits all)

Also different nozzles sit differently or better/worse on some tappets...

the clear cheapo cyma tappet is loose as f**k with a red SHS m4 nozzle

(hence me using a SHS tappet but needs modding up front with cut outs for cyma box)

What I might suggest is grab a SHS V2 tappet as these tappets retract most

might be a bit bent, so straighten the right angle up front in hot water to true 90 degrees

sand the front of tappet plate a bit, mod the sides up front to work in Cyma box

if you sand the tappet front edge on a table with emery paper it will return a whisker further

then you could carefully and very lightly sand the red M4 nozzle a whisker - just a whisker

but as you sanded the front it will return to seal on hop unit/bucking...

The new SHS tappet should retract further and allow a bb to chamber on a lightly sanded M4 nozzle

(that still returns to seal as tappet front is sanded a bit)

check for fin hitting axle of sector as in pic

you may need to file it very slightly and very carefully smack bang in line with axle

don't worry about not retracting long enough - delayers are not the solution to all feed issues

a friggin' DSG fin is so short it retracts for a split second then returns...

It is mostly about ensuring the tappet window is correct that is pulls back enough to chamber

allowing a sprung loaded bb to slip in and chamber to bucking etc....

It don't matter shit if you got a mega delayer - if there is only 5.5mm room

it will never chamber a 6mm bb past the nozzle

so a long nozzle throws stuff out and seals great but feeding is shit

or a shorter nozzle feeds great but seal is crap

a worn fin, incorrect nozzle, protruding bucking lips and f**k knows what else will cause feed issues

and V2 boxes have less overall retraction than V3's so on V2's the tappet window is more critical

Yeah I'd be tempted to get a SHS v2 tappet, start modding the cutouts for Cyma box

sand the front, check it is straight and 90 degrees, very very slightly sand the SHS M4 nozzle perhaps

open box up, check & mark where fin meets sector axle - file with tiny round craft file at exact point

check the tappet fully returns to front of box clearing the axle of sector as in pic

Also check the tappet in TOP part of box with cylinder head, sector gear etc...

check it doesn't bottom out on full retraction with cylinder head

(SHS tappets do retract more)

if delay clip is still on sector, check you don't feel a "bump" which is the delayer clip bumping the underside of tappet runner

right underneath as the cam/delayer starts to engage the top of fin...

if you feel this "bump" or slight resistance, then you need to lightly file the area about 1~3mm just in front of top of fin

on the underside of tappet runner by the fin...

BUT ONLY do this IF you feel a bump or resistance when testing in top half of box

*** NB ***

When I say 1~3mm I'm talking about the AREA or POSITION of AREA 1~3mm in front of fin

NOT file off up to 3mm in depth - there will hardly anything left and fin would just tear off

just a very light file around the few mm's just in front of tappet runner in front of fin

Literally a very small filing & sanding just where cam might bump the runner

If no "bump" is felt when testing it top of box - then don't worry about it, but important you check

Test the tappet operation in top half of box - sounds weird but just do it

When you test in the lower half there is too much play with sector wobble to truly check stuff

So checking the final tappet retraction is much more accurate in top half of box

(though you can't quite see the cam/fin operation, you see the full travel and feel for "bump")

When all that is done, ensure the fin doesn't get stopped by axle, mod if needed (quite likely)

then ensure smaller diameter shims are used as less likely to impede fin than jumbo shims

IF tappet is risking bottoming out on cylinder head....

and IF you used one like this....



Look carefully at bottom of head and there is a small ridge....

Take off the o-rings, plop on a shitty old nozzle

then file off that curved ridge at bottom CAREFULLY

clean up and refit o-rings etc...

Bit of f**king about but will gain you a potential extra 0.5mm to say 0.75mm or so space

so tappet won't bottom out of cylinder head when retracting to its furthest point

(the cylinder itself might be close to hitting the back of tappet but check in top box)

if cylinder is just starting to touch the tappet, you could just file it very very slightly

so that when you test (again in top half of box) it moves way way back

and the whole operation is met with no resistance, no "bumps" or bottoming out

and full complete return to front of box coz you carefully filed the fin by sector axle

THEN you have a tappet that retracts as far back as possible & smoothly returns fully

so you therefore have the largest tappet travel to give you a bigger tappet window

With the correct nozzle in there, you should get a great seal and reliably feed bb's even on so-so mags

THAT is about the best advice of everything I check for and nigh on every trick I have used to get max retraction etc...

BUT as always it is down to YOU to check all this crap out and see if it all operates smoothly and effectively etc....

The SHS tappet will retract the most

the round delayer I used in pic is brill, retracts more coz it has a bit of material over sector cam

BUT using this delayer on SHS tappets that retract more does often mean it can bottom out and risk bumping tappet runner underneath

It also retracts so much it bottoms out so need to give it some room to fully retract where ever possible

But after all this f**king about, plus the modding for Cyma v2 boxes

you will gain about 1mm extra retraction or just over that will greatly assist if not eliminate any feed issues

(at least from tappet/nozzle retraction - w@nky bucking or hop or assembly alignment is another issue)

As the V2's have about 1mm overall less tappet retraction than a V3

when stuff starts wearing like the fin, or nozzle spec or tolerances go just a tiny bit out of whack...

you get fps loss or pi$$ poor feeding coz the allowance for nozzle clearing & sealing is so close

As said if fin is worn, nozzle way too long, delayer will do little

if fin hits axle, the tappet won't 101% fully return to seal

so might need modding at axle area to ensure it returns

if you look at Cyma's blue tappet you see they chopped the axle area...



A SHS will need modding but found they retract a whisker more than other tappets

so check some $hit out, do some tests

order up a SHS tappet, use SHS M4 nozzle and do some tiny modifications for max tappet travel

You MUST check for bottoming out coz if you allow it you will lose a whisker of retraction

plus increased wear on fin or worse if tappet break/failure - so check $hit carefully !!!

best of luck

 

[Zarrin]

this TM compatible BS means next to nothing - some shit works but often it don't just drop in

many bits need checking and often a bit of sanding or tweak to ensure it works 101% as it should

Click to shrink...

 

[Sitting Duck]

Click to shrink...

well to be completely honest...

is fairly accurate at times

 

[matas17]

Hold up !!!!

this is an ongoing issue is it not ???







Now it "seems" that the cyma MP5 nozzle is a 21.4 ish nozzle...

https://www.airsoftforum.com/topic/241139-massive-air-seal-nozzle-leakeage-on-a-cyma-mp5sd/

so it seems 21.4 to 21.5 ish is required...

(also heard a Galaxy MP5k nozzle likes a SHS M4 too

but the "shoulder" of red SHS M4 is too fat so needs modding to nozzle shoulder

or modding/widen the Galaxy hop entry so chubby nozzle can operate smoothly)

in other words not all MP5 nozzles are the usual MP5 length

(different guns makes/hops work with different nozzle lengths than 1 size fits all)

Also different nozzles sit differently or better/worse on some tappets...

the clear cheapo cyma tappet is loose as f**k with a red SHS m4 nozzle

(hence me using a SHS tappet but needs modding up front with cut outs for cyma box)

What I might suggest is grab a SHS V2 tappet as these tappets retract most

might be a bit bent, so straighten the right angle up front in hot water to true 90 degrees

sand the front of tappet plate a bit, mod the sides up front to work in Cyma box

if you sand the tappet front edge on a table with emery paper it will return a whisker further

then you could carefully and very lightly sand the red M4 nozzle a whisker - just a whisker

but as you sanded the front it will return to seal on hop unit/bucking...

The new SHS tappet should retract further and allow a bb to chamber on a lightly sanded M4 nozzle

(that still returns to seal as tappet front is sanded a bit)

check for fin hitting axle of sector as in pic

you may need to file it very slightly and very carefully smack bang in line with axle

don't worry about not retracting long enough - delayers are not the solution to all feed issues

a friggin' DSG fin is so short it retracts for a split second then returns...

It is mostly about ensuring the tappet window is correct that is pulls back enough to chamber

allowing a sprung loaded bb to slip in and chamber to bucking etc....

It don't matter shit if you got a mega delayer - if there is only 5.5mm room

it will never chamber a 6mm bb past the nozzle

so a long nozzle throws stuff out and seals great but feeding is shit

or a shorter nozzle feeds great but seal is crap

a worn fin, incorrect nozzle, protruding bucking lips and f**k knows what else will cause feed issues

and V2 boxes have less overall retraction than V3's so on V2's the tappet window is more critical

Yeah I'd be tempted to get a SHS v2 tappet, start modding the cutouts for Cyma box

sand the front, check it is straight and 90 degrees, very very slightly sand the SHS M4 nozzle perhaps

open box up, check & mark where fin meets sector axle - file with tiny round craft file at exact point

check the tappet fully returns to front of box clearing the axle of sector as in pic

Also check the tappet in TOP part of box with cylinder head, sector gear etc...

check it doesn't bottom out on full retraction with cylinder head

(SHS tappets do retract more)

if delay clip is still on sector, check you don't feel a "bump" which is the delayer clip bumping the underside of tappet runner

right underneath as the cam/delayer starts to engage the top of fin...

if you feel this "bump" or slight resistance, then you need to lightly file the area about 1~3mm just in front of top of fin

on the underside of tappet runner by the fin...

BUT ONLY do this IF you feel a bump or resistance when testing in top half of box

*** NB ***

When I say 1~3mm I'm talking about the AREA or POSITION of AREA 1~3mm in front of fin

NOT file off up to 3mm in depth - there will hardly anything left and fin would just tear off

just a very light file around the few mm's just in front of tappet runner in front of fin

Literally a very small filing & sanding just where cam might bump the runner

If no "bump" is felt when testing it top of box - then don't worry about it, but important you check

Test the tappet operation in top half of box - sounds weird but just do it

When you test in the lower half there is too much play with sector wobble to truly check stuff

So checking the final tappet retraction is much more accurate in top half of box

(though you can't quite see the cam/fin operation, you see the full travel and feel for "bump")

When all that is done, ensure the fin doesn't get stopped by axle, mod if needed (quite likely)

then ensure smaller diameter shims are used as less likely to impede fin than jumbo shims

IF tappet is risking bottoming out on cylinder head....

and IF you used one like this....



Look carefully at bottom of head and there is a small ridge....

Take off the o-rings, plop on a shitty old nozzle

then file off that curved ridge at bottom CAREFULLY

clean up and refit o-rings etc...

Bit of f**king about but will gain you a potential extra 0.5mm to say 0.75mm or so space

so tappet won't bottom out of cylinder head when retracting to its furthest point

(the cylinder itself might be close to hitting the back of tappet but check in top box)

if cylinder is just starting to touch the tappet, you could just file it very very slightly

so that when you test (again in top half of box) it moves way way back

and the whole operation is met with no resistance, no "bumps" or bottoming out

and full complete return to front of box coz you carefully filed the fin by sector axle

THEN you have a tappet that retracts as far back as possible & smoothly returns fully

so you therefore have the largest tappet travel to give you a bigger tappet window

With the correct nozzle in there, you should get a great seal and reliably feed bb's even on so-so mags

THAT is about the best advice of everything I check for and nigh on every trick I have used to get max retraction etc...

BUT as always it is down to YOU to check all this crap out and see if it all operates smoothly and effectively etc....

The SHS tappet will retract the most

the round delayer I used in pic is brill, retracts more coz it has a bit of material over sector cam

BUT using this delayer on SHS tappets that retract more does often mean it can bottom out and risk bumping tappet runner underneath

It also retracts so much it bottoms out so need to give it some room to fully retract where ever possible

But after all this f**king about, plus the modding for Cyma v2 boxes

you will gain about 1mm extra retraction or just over that will greatly assist if not eliminate any feed issues

(at least from tappet/nozzle retraction - w@nky bucking or hop or assembly alignment is another issue)

As the V2's have about 1mm overall less tappet retraction than a V3

when stuff starts wearing like the fin, or nozzle spec or tolerances go just a tiny bit out of whack...

you get fps loss or pi$$ poor feeding coz the allowance for nozzle clearing & sealing is so close

As said if fin is worn, nozzle way too long, delayer will do little

if fin hits axle, the tappet won't 101% fully return to seal

so might need modding at axle area to ensure it returns

if you look at Cyma's blue tappet you see they chopped the axle area...



A SHS will need modding but found they retract a whisker more than other tappets

so check some $hit out, do some tests

order up a SHS tappet, use SHS M4 nozzle and do some tiny modifications for max tappet travel

You MUST check for bottoming out coz if you allow it you will lose a whisker of retraction

plus increased wear on fin or worse if tappet break/failure - so check $hit carefully !!!

best of luck

Click to shrink...

Found an issue that had to do with tappet plate as you noted and also hop unit which for some odd reason likes to move back and forth inside receiver like 5cm, No idea why but that seems to cause the issue with the fps drops. Seems like sometimes it goes up to 340fps and then down to 220fps for that reason alone. Gone try and figure out tomorrow which position hop unit has to be in for gun to have decent fps.

 

[Sitting Duck]

try and figure out tomorrow which position hop unit has to be in for gun to have decent fps.

Click to shrink...

Usually up against the gearbox, many find gives the best results

I've done the 3 hand chrono test a few times to check stuff out before I sling it back in gun

or to confirm a process of elimination etc...

but shifty hops in some guns can cause fps drops, hence things like springs/o-rings on hops

help to ensure some shifty hops stay put or in place better

other hops on different guns are more fastened in place like on AK's

but M4's often benefit from a spring(s) or o-ring mod

and/or o-ring method...

just to stop the hop trying to come forward when say a mag is inserted

thus pulling it away from box and creating a leak that drops fps etc...

 

[matas17]

Usually up against the gearbox, many find gives the best results

I've done the 3 hand chrono test a few times to check stuff out before I sling it back in gun

or to confirm a process of elimination etc...

but shifty hops in some guns can cause fps drops, hence things like springs/o-rings on hops

help to ensure some shifty hops stay put or in place better

other hops on different guns are more fastened in place like on AK's

but M4's often benefit from a spring(s) or o-ring mod



and/or o-ring method...



just to stop the hop trying to come forward when say a mag is inserted

thus pulling it away from box and creating a leak that drops fps etc...

Click to shrink...

the thing is there is not space for spring to push hop unit back towards gearbox so im still trying to figure out the way to keep it in place as the spot where hop unit sits is really open and barrel spring would need to be really long to push against hop unit and outer barrel which attaches to this. Metal spacer/hop unit holder. And also if I can't sort this out what brand mp5 would you recommend me getting instead of this cyma. as I already spent months trying to fix this problem.

 

[Rogerborg]

The only thing I can suggest is checking that the barrel is right in, and clipped into the hop.  On my Galaxy / JG clone MP5K, it's an absolute sod to get the barrel and rubber to go deep enough into the hop unit to get the securing clip on.

 

[RonLancs]

I had the same problem barring all the upgrades. I put a SHS M4 nozzle in. I couldn’t feel the resistance when I put the box into the hop and there was resistance when moving the nozzle manually on the cylinder head.
 

I replaced the stock nozzle and after a new O-ring and a lube I’m getting 320 FPS with 6 FPS variation. I find CYMA nice and easy to work on. 
 

Thanks guys 

Ron