Airsoft Forums UK

it's an annoying operation for sure.

i tend to find right hand fingers down on the cylinder, hold it in position.

once you've got the spring guide in it's notch in the lower half, you can use a screwdriver through the hole in the back to hold it angled slightly down usually stops it jumping free (most gearboxes have a rear hole for this, although i've met ones that don't) leaving your right hand sufficiently free to pick up and place the gearbox casing.

really difficult to describe with words, it's the kinda thing you just have to pick up by feel but hopefully that made at least a little sense.

of course it's exactly at that last point that the trigger, anti reversal latch or both jump free, forcing you to reset.

the anti reversal latch in particular hates playing ball, always loves to jump free at the last minute. backing the geartrain into it can provide just enough tension to stop this, or if it's a real bugger then a magnet on the underside will hold it down for you.

I have already learnt a lot of these "hard" lessons, took me a good hour to figure out how the trigger went back together after catching it and exploding it across the table.

Is it normal for the spring to bunch up inside the piston? Like it looks like it's compressing so aggressively it couldn't even compress under motor power, also which bit of the casing does the ARL spring hook around?

My spring guide looks like three washers on the end making it longer, there's a screw which goes through the centre which looks like, you could remove those washers but it's completely seized. Does this sound like an aftermarket part?

I built a jig to hold various bits in place while I worked on my F2000
 



Page 2 has a pic of my cunning design to hold the spring in place while jiggling all the other bits.
 

The takeaway message of all these shenanigans was "buy a gnu with a Quick Change Spring system" or suffer the consequences.

My whole plan was to buy a gun made by CYMA for exactly this reason, cost, simplicity, and availability of parts. Something easy to learn on, why does it have to be the only gun with no quick change spring ?

@RostokMcSpoons  I just read through your thread and you literally experienced every problem I am, this fills me with confidence I have no scuffed it beyond my ability to repair. I am absolutely terrified of damaging the Titan whilst fiddling with the trigger though, should I be, are they quite hardy generally? 

are the 3 washers you describe on the rear end of the spring guide like this:

https://www.ak2m4.co.uk/internal-parts/spring-guides/zci-spring-guide-stainless-steel-qd-gearbox

if so that's a thrust bearing (sometimes they are just washers that sorta kinda do the same job), you'll often find aftermarket pistons have something similar.

it's a common aftermarket part (and a bunch of stock guns come with them). generally you want at least one end of the spring on a thrust bearing (both is kinda redundant) and i prefer having them on the spring guide as it's extra weight on the piston that doesn't need to be there.

if the washers are halfway along the spring guide like this;

https://airsoftdirect.uk.com/shs-aeg-dsg-spring-guide-v2-stainless-wd0033/

then it's a DSG spring guide designed to add more spring preload to compensate for a dual sector gear build where you're only getting half the stroke of spring compression. personally i'm not keen on the idea reckon a stronger spring with a standard guide is the way to go, but this would explain the spring being particularly nasty to try and fit as you're putting it under even more preload than normal.

it's common for spring guides (wether or not they have a thrust bearing) to not have a hole all the way through, although generally there's a bolt hole of some description to get a little purchase.

whilst it's a pain in the ass learning on a non qd, think of how glorious working on your first qd box is gonna be......

what's brand is the M95?  how long is it?  If it's my XT one then should be pretty easy to install

I have no experience with the Titan, or any other optical MOSFET, so I'll let someone else tell you.

What I can say is my gun misbehaved enough that I stopped working on it, and have asked for quotes from techs on fixing it for me.   It runs like a beast when it runs, but at the moment it's locked up, has been for a while so it's probably killed the spring.  I'm feeling a bit more motivated to have another go, but first I'll do some simple jobs (changing bucking and nubs on other guns) before returning to it.

Making the jig was a little time very well spent, as trying to get everything fixed when you've only got your two hands on it can feel impossible

Good luck

I DID IT!

It's all back together and shooting, still exactly 213FPS on an M95, it's exactly the same ~5fps which is super weird, where else could I be loosing so much power?

@ak2m4it's a ZCI M95, might have to place an order for full internals from you at this rate. Here is a photo of the internals, might help identify what is in here, it's an SHS motor and gears. Some sort of orange ported piston head with a nipple on it

Getting it back together so it still works is a good effort!   ?

Did you check the piston / cylinder is actually air-tight?
And make sure the hop rubber is intact, with the spring on the barrel in front of the hop unit, to push it back into contact with the nozzle

I have a Combat Union CNC hop which screws to the front of the gearbox, it can't move at all it also screws into the outer barrel assembly. Checked the barrel, hop etc, all clear and looks brand new.

In terms of airtightness it wasn't like putting your finger over a syringe and pulling, but it did puff some air out the nozzle when I pushed it in fast... I don't really have a gauge for what good airseal feels like...

TBH that air seal sounds ... fine...?  Others might disagree though.  Certainly not the reason to be down at ~210fps.  
Your fancy hop up unit is waaaaay out of my league / experience!  I've just dealt with standard plastic rotary and M4 units so far.

Ah, sounds like air seal.  Tappet plate + nozzle + hop + bucking = seal.  Change any of those and you can get misfeeds or a big power loss from a fraction of a mm of difference either way. Change more than 1 at a time and you don't know what caused it.

I'm trying to picture how the hop can screw to the gearbox and the upper/barrel.  Normally you'd have a spring pushing it back against the gearbox.

First thing I'd do is put the CYMA hop back in and see what it's chronoing at, with some hop applied.

Maple Leaf buckings have longish lips and tend to give good air seal (sometimes at the cost of misfeeding, but that can be sorted by trimming a tiny sliver off the bottom of the feed lip).

If you do end up going back into the gearbox, you'll definitely want to check the airseal there.

With the cylinder out of the gearbox, put the cylinder head in, the nozzle on the head, and the tappet plate on the nozzle (to help hold everything square).  Pop the piston in, put a thumb over the nozzle, and push the piston sharply forwards (or rest the rear of the piston on a table push the cylinder assembly down on the piston). It should be stopped by the airseal, or be very hard to push.  If you can creep the piston in, that's not such a big deal, it only really matters what happens when you do it quickly.

If you've got poor airseal in the cylinder, you can replace the piston and cylinder head rings, or stretch them: remove from the piston and head, stretch over the cylinder and leave them for a bit, and/or apply heat.  Reassemble with silicone grease (or red rubber grease, but nothing petroleum based).

It's quite remarkable how big a difference airseal makes: I saw 1.3J out of an M100 spring using a completely stock (but stretched and greased) CYMA gearbox, a ZCI hop unit, maple leaf and 229mm ZCI barrel.  Ooops!

@Rogerborg the combat union hop barrel retention is truly ridiculous, on top of a metal c clip with grub screw retainer it has a collet that properly clamps down on the barrel and locks it solid.

I unfortunately do no have the CYMA hop unit to put back in to it. @Adolf Hamsterwhen you say ridiculous, like in a good way, or in a terrible design way?

I've just ordered a complete set of internals less a spring, gears and MOSFET, hopefully I can get it into a working state early next week. 

I feel for you man. I’ll confess, it took me four hours to reassemble my first gearbox. Not doing any mods or replacements or shimming or anything. Just getting the dang shell back together took me four hours to figure out!

You wanna know what’s even worse? It was a Lancer shell with a QD spring guide. ?

Don’t worry though, it’ll come to you. At this point I causally install M130 springs in standard shells with nothing more than a screwdriver. It’s a matter of feel, as others have mentioned.

On the topic of your FPS… try getting a different spring, if nothing else works. A lot of manufacturers make their springs to bad standards, and as such FPS can be a little everywhere. Notice how on Evike and such they’ll say crap like; “M120 spring: 350 to 420 FPS”? That’s crap. Springs should not have a 70 FPS margin of error. And yet they do. The bad ones at least. Try out a Guarder or PDI if you decide to try a spring replace. Do the other stuff first.

I'd expect that that suggested range is more down to the other variables (airseal, cylinder-to-barrel volume, magic dust) than an admission that the spring itself isn't consistent.

Not that I'm claiming that airsoft parts are consistent, I hasten to add!

@BreadyC it's a good thing to have the barrel locked down that well, for accuracy.