Kublai CYMA WAT full metal MK18 teardown

I have the 91/2” version and here’s my experience…

Pic of how it looks at the moment. (Doing an AFP build)

The upper and lower receiver have good fitment to each other and the mouldings seem pretty good. Everything that attaches to it on the outside seems OK too.

The upper rail on the hand guard and the upper rail on the upper receiver are not the same shape as each other but meh… it works…

Only real issue on the out side out of the box was my buffer tube was VERY loose and had to be tightened

The orange tip is not only screwed on (14mm reverse thread) and pinned it’s also glued !!! It has to be destroyed to get it off.

Internals wise, it’s not as good. But it’s very easy to sort…

But before that heres a little back story…

I got this from GBU it was delivered in its box with no covering at all just the standard Kublai box (without its outer sleeve !) just taped closed… which I think is not a good idea… When sending blasters through the mail, I think it should have discreet wrapping on it… but anyways that’s just my opinion…

I took the blaster out of the box, found the loose buffer tube and sorted it… I then changed the mini Tamiya plug over to a Deans and wired it correctly. Connected up a spare 7.4v battery, loaded up the mag with some AKA’s… Set it to semi auto and pulled the trigger a few times and could instantly tell it wasn’t right… it feeds with no problems and besides it sounding like it had a bucket of bolt inside it you could tell it was inconsistent with its FPS to the point where some gels weren’t fair off just falling out of the barrel and others looked and sounded quite powerful…

So I hooked up my Lighter BT and quickly discovered I was right… I put about another 10 gels through it on semi and was getting anywhere from 90 to 275 FPS… it was all over the shop with most being in the very low 100’s. In full auto it was a little better with an average of around 200 FPS with its highest being a 281 and it’s lowest still being in the 90’s… so in total I put about 60 gels through it mostly in full auto and then decided it’s time to pull this thing down and work out what’s wrong with it. So here’s what I found.

Internal specs…
The alloy barrel is 300mm long with an ID of 7.5mm.
The cylinder is 72mm x 23.75mm and is not ported at all, so it’s a 100% cylinder.
The spring is a 1.3mm
The cylinder head is plastic with a metal nozzle and is factory glued into the cylinder.
The piston and piston head are plastic with only the last tooth being metal.
The air nozzle is plastic and has no o-ring inside it…
It has 18:1 metal gears and a metal anti reverse latch
It has a full metal gearbox shell (this is actually quite good)
It has a metal spring helper
It also has bearings
And also comes with a basic black metal trigger…

The listing s say it has a high torque motor… it has the same stock motor most of these things come with… it looks identical to the one that came with my HK from LDT…

Once I started to pull it down I also notices that the two mag terminal wires were starting to rub through
from the mag itself rubbing on it. This was caused by them being way to short and were pulled very tight and as I had only inserted the mag once this was not a good start lol. By the time I got the box out of the lower the black wire had actually broken off the terminal…

Once the box was out I stripped It down to reveal it inners.

It was a little dirty in there not sure what from but yeah… I also noticed no shimming at all, obviously the reason for the bucket of bolts noise!!.. I removed the piston/cylinder setup and tried for some compression and found non… I could literally push the piston in with the tip of my pinky with no effort at all…

Here’s a pic of the inside, notice it’s not clean in there it also has very little grease/lube. You can also see I’ve replace the mag terminal wires with some high quality OFC silicone wire…

So I tried a green o-ring, no change… I cleaned up the mould a little on the piston head as it’s not the best, this made the slightest of change but still I could push it in with my pinky with no effort… so I grabs the stock plastic piston head I had spare from my LDT HK416D and installed that and reinstalled the stock black o-ring that came with the MK18 and bingo we had some decent compression… I then installed the new green o-ring and it was perfect… good strong compression and it held till you let it off…

Here’s a pic of the cylinder I also ran a bead of thick ZAPP glue around the join between the head and cylinder to make sure there were no leaks…

Here’s a pic of the piston heads… the HK one looks worse then the MK18s one but at least it works
Not sure if the MK one has a crack or if it’s just the o-ring slot is not wide enough to allow the o-ring to move around and do its job or what but it doesn’t work thats for sure…

Here’s a pic of the piston with the “new” head on it but still the stock o-ring at that point… notice the single metal tooth !

So next I set out on the shim job… I got this pretty spot on, no up and down movement and still spins freely… But damn it needed some shims. Over 1mm on one side of each gear… there is now about 1.5mm of shimming in total on each gear but hey the box is now very quite…

The other issue inside the box is the AOE… it was way off too… about 2mm in spacing is now used and the AOE is pretty good not perfect but pretty close…

Here’s a pic of the corrected AOE… I also had to file down the second tooth on the rack for clearance and I also angle filed the last (metal) tooth to minimise the notchiness as the last tooth slips off…

Here’s a pic of the box ready to go. At this point I just had to strip it down completely and give it a good clean out then re grease, re lube and re assemble. You can also see I swapped out the trigger for a Red CNC’d one…

And here’s a few of the completed box…

That’s about it, it’s not much work to sort this box out and get the blaster working perfectly, actually it works better then advertised…

Here’s some pics of the FPS etc it now pushes… as you can see it’s higher then advertised and it’s also now very consistent…

Semi auto

Full auto

As you can see it’s averaging over 290FPS in both semi and full auto with the stock motor and spring…

Only things I would do to this box is swap to a full metal racked piston for the extra reliability and swap to an o-ringed air nozzle for maybe a few extra FPS…

Reason I say “I would” do to it instead of “am doing” to it is because I’m not going to be using this box as I had already started to build a high FPS, high RPS box using a MK tactical V2 CNC’d box for this build and I’ll be using that instead… I will be selling this box if someone is interested, let me know… it’s only had around 100 gels put through it… :ok_hand:t2: But I’ll put up a forsale post after about that…

Anyway’s, that’s my experience with this awesome little blaster… out of the box it was a little iffy but with very little work it’s a beast… I just class it as a little less mass produced and a little more hand built.

11 Likes

Good work. You have answered a lot of questions. So thanks.
I was so close to getting one but I ended up with a metal/ wood ak74 instead. Now after your write up I might have to get both. Lol

1 Like

How much for the box and would you post?

Hey Michael, I’ve sent you a PM…

I’m actually looking for this gearbox to properly fit into my WAT/Kublai metal M4 receiver. I’ve tried a few other gearboxes (Warinterest v2 and Kublai v2 Nylon) and the fit is too tight on the charging bolt so I can’t use the charging handle smoothly.

I have the same reciever and the kublai v2 box fits mine no problem

Just read your break down. Thank you for taking the time to write it up. I am considering doing the same thing. Cheers

1 Like

looking great! i just got my 12" tan today. any suggestions/tips for taking the tip off? would like to keep it orange tip just in case

Cheers man.

Ummm. Seriously the only way to get the orange tip off is to destroy it !!! Well thats the only way I found anyways.

I really don’t think they want you to take it off.

It’s screwed on then pined… They also pack the threads full of glue !!

The pin is also a one way in, same way out setup from memory. So you can’t just hammer the pin right through. I couldn’t get a hold of it at all with anything to pull it out. I even Dremeled around the pin so I could try and grab it with needle nose pliers and I still couldn’t budge it… I think the glue had also ran down in there too and glued the pin in.

Also tried heat… No go there either. The amount of heat it took to soften the glue was more then the plastic could handle.

Even though I never intended using this tip I did try my best to save it but to no avail.

It ended up in about 15 pieces by the time I got it off and then it took some time to clean all the glue out of the threads…

I purchased a black metal one (not the plastic one in the above pic!!) that is almost identical to the factory orange one from monkeymods. … looks mint…

thanks! yeah i was looking at it, and it is really stuck on there hey? sorry for more questions! but when you did your tear down, did it look like the bolt release look like it interacted with the Faux-Bolt cover?

I nearly destroyed my barrel trying to get the orange tip off but found placing it in a pot of boiling water for 5 minutes make it a lot easier to unscrew.

1 Like

It does look like it should but mine doesn’t either.

I thought I had seen in one of the videos that it worked but I’m not 100% (I watch so many GB vids lol). But yeah it definitely looks like it was there intention to have the cover move / lock… I wish it did have this feature, even though just a gimmick it still would have been Kool.

@ROGBoy Thanks for the detailed post & photos, it’s exactly what I needed to troubleshoot my WAT/Kublai Omega 7″ which is my first blaster.

I had the same issue with the loose buffer tube and mine also sounds like it has a “bucket of bolts inside” :joy:

Interestingly we seem to have a different piston setup:

I’m not 100% sure how snug the piston is meant to fit inside the cylinder, but mine is very loose with very little (if any) seal which I suspect is the main issue with mine.

Does yours empty a full mag? I always have at least 1/4 of gels left in mine and often doesn’t fire even when the mag is full.


I was thinking I might buy the KUBLAI CNC One Piece Cylinder/Head or this set that I found on eBay

2 Likes

Its the piston head. My stock one was useless, drilled the holes out and widened the oring groove and it has compression now but still leaks. Swapped to a different head, voila. Rock hard even with no lube.
That doesnt sound right…

3 Likes

@DexEfx909

Glad I could help…

Wow your entire piston is different to mine.

Mine only had the last tooth as metal not the whole rack and mine also only had a crappy plastic head on it which was most of my issues. Your piston should be fine. Just throw a good (maybe green) o-ring on it and you should have good compression…

I never had issues with feeding at all with mine… although I must admit I never used the stock metal mag that came with it… just didn’t like it at all. Looks, fit and finish, nothing, so I didn’t use it… I’ve only used a warinterest mag in mine, both a standard one and a glow one and yeah never had an issue. The WI Mags fits much better also…

I’m also not using the standard box in mine anymore. I fixed / sorted the standard box, got it working perfectly then removed it to install my MK V2 setup I have in it. The stock box will go up for sale, just need to get around to listing it.

I’m using the one piece cylinder you listed in my MK V2 box !! Works Perfect !! Also not sure if I’d like to use one of them alloy pistons in that kit you listed in a metal box. That metal on metal rubbing even with lube just doesn’t seem like a good idea to me…

@Gunge

Did yours come with the alloy piston head and full metal rack like DexEfx909’s did Or a plastic setup like mine did ?

1 Like

Plastic with one metal tooth. Came out of the mk18, exactly like yours

1 Like

Great, looks like I need to add a WarInterest mag to my order!

1 Like

Ok yeah. So same issue as mine…

The stock plastic piston head is rubbish.

Swapping it out for another stock plastic one from my LDT HK416D V3 I had laying around sorted it though.

@DexEfx909

Where did you buy yours from ?? I got mine from GBU

I found a seller on eBay who had them in all sizes/colours for sale.

1 Like

Thanks mate, great break down. Would you know which t-piece and nozzle (other than Kublai) will fit this? I ordered the 7" mk18 version and wanted to get a new barrel and a t-piece in advance.

1 Like