Cybergun F2000 (Cyma) - Internal upgrades / tinkering

[RostokMcSpoons]

Update...

Wiring done after a bit of faffing about I decided "sod it" and just put it together.  
Motor spins (oooooh it's gone some oomph) when I move the trigger shuttle into contact.

So that's that. 

Assembled the piston, cylinder and cylinder head.

Here's a disappointment.

I get a better air seal with the old piston than the fancy new one.  Is there anything I could do to improve it?
I'm using Silverhook Silicone Grease as my lube, would something different (thicker?) improve the air seal?

Next job is shimming.  This one frightens me, having watched the how-to videos.  I don't have a viewing port in the gearbox to check the bevel and pinion engagement so it'll be a degree of guesswork right from the start, which doesn't sit well when I know that a 0.15mm shim might make all the difference.  And as my level of intuition will be like Joey Essex trying to guess the answers in a exam on orbital mechanics, I'm probably going to mess it up, aren't I? 

 

[Adolf Hamster]

Ok, my battery is already Deans connector, I sorted that out a while ago, its fine.

just match to the battery then.

tamiya connectors can be weird in airsoft, they tend to be wired reverse to RC batteries so it's not a given that the colours match. presumably for the same reason as the eclectic wire colouring- because electrical engineers are a strange bunch.

as long as you keep track in your mind (write it down if needs be) which goes where then that'll do the job. if the motor runs backwards just swap the wires over problem solved.

Assembled the piston, cylinder and cylinder head.

Here's a disappointment.

I get a better air seal with the old piston than the fancy new one.  Is there anything I could do to improve it?
I'm using Silverhook Silicone Grease as my lube, would something different (thicker?) improve the air seal?

you could try swapping the o rings over, see if that does it, there's other tricks like stretching the o rings or swapping them out for one slightly oversize.

that's an alu head isn't it? i know some of the plastic mushroom heads have issues with the texture of the plastic giving a poor seal but the alu one shouldn't.

Next job is shimming.  This one frightens me, having watched the how-to videos.  I don't have a viewing port in the gearbox to check the bevel and pinion engagement so it'll be a degree of guesswork right from the start, which doesn't sit well when I know that a 0.15mm shim might make all the difference.  And as my level of intuition will be like Joey Essex trying to guess the answers in a exam on orbital mechanics, I'm probably going to mess it up, aren't I? 

never needed to cut a window and the only box i've had the luxury of viewing the motor mesh is the open bottomed a&k mg boxes, which funnily enough are awful for accumulating dirt+crap in them.

start by getting the idler and sector shimmed down as far as they'll go (working on the left hand half of the box) and such that they're running free even when the box is tightened up and tilted all different directions.

that'll give you the most wiggle room on the bevel to go up/down as needed, then shim that as above (so you know your starting point of say 1mm total, then you can swap shims from one side to the other to move it up and down)

you can try the bevel in the right half with the motor cage in position to give a very rough starting point, then it's just try it, adjust, try it again.

running the motor with just the gears can give an idea of how much noise there is, how smooth everything is sounding etc.

once you've got the bevel height where you want it, check how much overlap there is between the pinion and the idler and if necessary raise the idler/sector just to keep a decent overlap (ie that you're not driving on only half the teeth)

 

[RostokMcSpoons]

Swapping the O rings was a good shout, but didn't work.  The new one is quite weedy and loose compared to the old one, but they seem to do as well each other in action.

So it's weird, the old piston is still better. 

When the nozzle goes on, both let air through quickly though, so in the end I'm wondering if it's worth chasing a great seal, when it all goes to pot anyway

 

[Asomodai]

Update...

Wiring done after a bit of faffing about I decided "sod it" and just put it together.  
Motor spins (oooooh it's gone some oomph) when I move the trigger shuttle into contact.

So that's that. 

Assembled the piston, cylinder and cylinder head.

Here's a disappointment.

I get a better air seal with the old piston than the fancy new one.  Is there anything I could do to improve it?
I'm using Silverhook Silicone Grease as my lube, would something different (thicker?) improve the air seal?

Piston or Piston head? If piston head then use the O-Ring from the old piston head on the new one.

 

[RostokMcSpoons]

I might just run the old piston in the new cylinder, see how that pans out.

For the interest of any tech-noobs who might read this thread in the future, I amended my jig.  A couple of wood screws and an allen key go into the spring guide as I'm assembling the gearbox.   I then wedge a screwdriver in under the allen key, to the left of the screws to create a levering force to keep the guide down in the shell,  so a single finger of pressure on the cylinder is all that's required to keep things in place while I manipulate the top half and snap it down.

View attachment 83271

(Also used the internal screw to extend the the spring guide to its longest length, to tame the spring from jumping out sideways)

 

[RostokMcSpoons]

IT'S ALIVE

(Thanks feck for that!)

Now my problem is that it's running a little on the spicy side!  360-370fps with 0.20g.
The hop unit doesn't appear to impinge much on the barrel, even when fully on, so hop adjustment might not be enough to tame the beast I have created.  I may have to get an M95 and fit that.

But the motor seems to be running smoothly, and snappily, even on the half-charged NimH 1600mAH 8.4v I've been testing with.  When I slap on a Mosfet and plug in the 11.1v Li-Po it should be awesome

I have had one jam in the barrel, hopefully that's just down to the crappy 0.20g BB's I'm using

 

[ak2m4]

@RostokMcSpoons you've put it together already but check the air vents of the piston head, make sure they are clear.  It's easy to over-lube and block resulting in the oring being able to push out.

 

[RostokMcSpoons]

@RostokMcSpoons you've put it together already but check the air vents of the piston head, make sure they are clear.  It's easy to over-lube and block resulting in the oring being able to push out.

If anything the whole thing is under lubed at the moment.  I'll do a bit of test shooting with it then I'll take it apart again to apply some better grease. 

I could swap the piston over (I'm using the old one as I didn't have to worry about engagement) to see how that affects muzzle velocity as I've obviously got some excess to spare (rather than swapping the spring)

Edit:

I've wound out the 'quick fps adjuster' screw in the spring guide and I'm getting down to 345-355fps with some hop applied, so maybe the spring is alright as-is, but I've ordered two lots of silicon grease (one for the gears, one for the piston) from good ol' AK2M4 so I'll still be opening it up again anyway.  I'm no longer filled with fear by the internals of an airsoft gun.   This must be a good thing  (Or a bad thing for my bank balance, as I'll be prepared to change more stuff!)

It's firing at a healthy 14.3 rps with the Titan 7.4v Li-Ion.

I've definitely got a double-feed issue on full auto with my old Classic Army STANAG mag, which is the one I've been filling with the 0.20g BBs for all my chrono testing.  I've twice (in the space of a couple of hundred shots) had the barrel end up with several BBs inside.   That's a sub-optimal scenario right there.
I've only fired a few bursts through the gun with the supplied hi cap and one of my other STANAGs, they seemed ok so it might just be finicky with the mags, but I'm really going to need to 'let loose' to see how much of an issue there is.

Edit2:  Pinged a good few rounds on full auto with the provided hi cap mag, no problems with that one at least!

 

[RostokMcSpoons]

(Replying to @Skara in the "What have you just bought" thread...)

Cheers, I may well be able to drag the FPS under the site limit just by winding out the last of the adjustable spring guide doohickey, I've not undone 'freely' because I didn't want to wind the screw all the way out and have it rattling around... but when I crack open the gearbox to re-lube the gears and piston, I might find there's plenty of adjustment left.

If that's not the case, then presumably the 420mm barrel + un-ported cylinder counts as "plenty of volume"?

 

[Asomodai]

(Replying to @Skara in the "What have you just bought" thread...)

Cheers, I may well be able to drag the FPS under the site limit just by winding out the last of the adjustable spring guide doohickey, I've not undone 'freely' because I didn't want to wind the screw all the way out and have it rattling around... but when I crack open the gearbox to re-lube the gears and piston, I might find there's plenty of adjustment left.

If that's not the case, then presumably the 420mm barrel + un-ported cylinder counts as "plenty of volume"?

I would snip the spring shorter before short stroking one tooth. Keep your Volume where possible. 

 

[RostokMcSpoons]

Quick question, because the next step is trying to cut a slot in the hand guard, to fix a RIS rail into it....

How do you take the front hand guard off?  

It looks like I just need to take the main locking pin out and then slide the barrel assembly off.  And then push down on the handguard from the inside.  

But I don't want to push too hard in case I'm going to snap some clips (and I need as much stability there as possible)

A quick pointer in the right direction would be much appreciated ?

 

[Adolf Hamster]

Unless cyma have decided to be weird about it, and i dont see why they would then that is how its supposed to come off (copies the original)

 

[RostokMcSpoons]

Unless cyma have decided to be weird about it, and i dont see why they would then that is how its supposed to come off (copies the original)

Thanks, with that you gave me the confidence to use a screwdriver to lever it gently away from the rest of the body.  The front lugs were sticky, but there aren't any latches or anything, just a slight excess of friction.

Here's what I'm trying to achieve...
View attachment 83431

... but I'm really not attempting to get a copy of that, so no need for the tri-rail look, it's just getting a stubby grip fitted solidly to the front.
In fact that's quite a low fitting, I'd rather have it nearer to the barrel axis, so it could go further forward to help with that.  (Not sure if the drawing of the grip, which I borrowed from an MP5K plan, is properly to scale)

View attachment 83432

There's a cheap stubby on Amazon that I'm willing to hack to bits, if necessary

https://www.amazon.co.uk/Element-Style-Stubby-Airsoft-Paintball/dp/B01N9LSV12/ref=sr_1_28

View attachment 83433

Here's what I'm working with inside the foregrip...

View attachment 83434

I can grab a cheap 12cm length of RIS rail from my local retailer (Action Hobbies), and then it becomes a matter of dremelling a slot to hold the RIS with the grip in place, stabilising it the inside (maybe just need some woodwork screwed in place to the guard + body?)

Is this all a silly thing to attempt, or have I "got a shot at the title"?

 

[RostokMcSpoons]

Well I said I didn't need the Tri rail look, but I just found this at Ant-Supplies...

https://www.ant-supplies.uk/rifle-bipod-fittings/tri-rail-spigot-adapter.html

View attachment 83464

I'm not sure if the spigot makes it easier or harder to mount into the handguard, but it sure looks the same as the game...

Edit: found another of my pics from the game... yeah it's a little different, and I can see the game's version would be a simpler fit (just in terms of square sections where they intersect through the handguard versus the more complex outlines of the spigot version).   

View attachment 82747

It's not going to be super-easy, might go back to a simple piece of rail and some relief cuts for the grip itself.   Grip on order, won't turn up for another week though.

Edit:  For completeness, here's the finished work:  a simple piece of rail fixed into the handguard, with the stubby grip attached.

View attachment 84626

 

[RostokMcSpoons]

Quick question:   Is there any easy way to make the cross-bolt a bit stickier within the body?  Depending on how hard the upper receiver is pushed back (and I'm guessing the difference is less than a millimetre), that bolt can either be nicely held in place and requiring a decent push to remove it, or so loose it could almost fall out.
Is there anything I can do to the bolt or its slot, or do I need to shim the whole upper receiver a little forward?

 

[Adolf Hamster]

Try some o rings to space the hop unit against the gearbox, not too many though as you dont want to put too much load on the hop

 

[RostokMcSpoons]

Try some o rings to space the hop unit against the gearbox, not too many though as you dont want to put too much load on the hop

I actually need to shim the upper receiver away from the gearbox though - it's having it ~0.5mm forward that puts the resistance on the cross bolt. Is putting o-rings on the gearbox side of the hop unit going to stay in place?  And do that shimming job?

Also... the hop unit feels quite... crap.  I spin the wheel, it goes from no hop to 'a bit'.  And then back to zero again (with a little click).  It doesn't have any positivity or resistance to it.
Now obviously I'm only shooting at 15m, I have no idea if it's actually doing a decent job in spite of that cheap feel... but should I just go ahead with a new hop unit?
@Asomodai would you recommend the G&G metal unit?

 

[Adolf Hamster]

I actually need to shim the upper receiver away from the gearbox though - it's having it ~0.5mm forward that puts the resistance on the cross bolt. Is putting o-rings on the gearbox side of the hop unit going to stay in place?  And do that shimming job?

Also... the hop unit feels quite... crap.  I spin the wheel, it goes from no hop to 'a bit'.  And then back to zero again (with a little click).  It doesn't have any positivity or resistance to it.
Now obviously I'm only shooting at 15m, I have no idea if it's actually doing a decent job in spite of that cheap feel... but should I just go ahead with a new hop unit?
@Asomodai would you recommend the G&G metal unit?

i mean o rings between the front of the hop (around the inner barrel) to push the hop unit back from the upper (and by the inverse push the upper forward from the hop unit)

it's the same tactic you'd use in most guns to ensure the hop is tight to the box so you get a more consistent seal.

 

[Asomodai]

I actually need to shim the upper receiver away from the gearbox though - it's having it ~0.5mm forward that puts the resistance on the cross bolt. Is putting o-rings on the gearbox side of the hop unit going to stay in place?  And do that shimming job?

Also... the hop unit feels quite... crap.  I spin the wheel, it goes from no hop to 'a bit'.  And then back to zero again (with a little click).  It doesn't have any positivity or resistance to it.
Now obviously I'm only shooting at 15m, I have no idea if it's actually doing a decent job in spite of that cheap feel... but should I just go ahead with a new hop unit?
@Asomodai would you recommend the G&G metal unit?

Yeah the G&G M14 unit is perfectly fine. It might change your air seal characteristics but didn't seem to affect mine. 

 

[RostokMcSpoons]

I mentioned this in the 'how did your day go' thread, but I found the hop unit was doing approximately 'bugger all'.   So although my gun seems fine at 15m, it's not hopping and consequently can't reach out past 30m.  So time to get a new hop unit in there.

So I have a couple of options...

Either this lot:
View attachment 84623

I could swap the bucking and nub for the usual Omega / Macaron combo of course
 

or one of these

View attachment 84624

which is a bit pricey but looks like it's got everything and should therefore be well matched ...?

Which option is the better way to go?