CYMA P90 full upgrade - Finished... For now...

[Iceni]

but if I short stroked, the Tappet wouldn't have enough time to push the Air nozzle fully forward before being pulled back again for the next round?

No the piston would fire before the tappet plate/air nozzle had returned to 0. So you would have constant airleaks from the hop unit, and the BB would not be getting pushed fully into and past the feedlips of the bucking, so inconsistent hop as well.

The tappet plate/Air nozzle are always on components. They don't spring back, or fire forwards. They ride on a constant surface of the Chip and the shaft. The tappet plate never looses contact with that surface, It's held on with spring tension.

If the surface is not the correct shape and the nozzle is retracted when the piston fires it won't hurt anything in the gun, but the BB will not be in the correct place and the airseal will not be perfect.

 

[Asomodai]

No the piston would fire before the tappet plate/air nozzle had returned to 0. So you would have constant airleaks from the hop unit, and the BB would not be getting pushed fully into and past the feedlips of the bucking, so inconsistent hop as well.

Why would a manufacturer make and sell such a massive Delayer Chip? To prevent a massive case of pre-engagement? 

 

[Iceni]

No idea TBF. I could see it causing problems for a lot of builds. There are other designs of chip that are better suited for short stroke systems. Have a look for the Lonex disc type. That big chip shouldn't be a problem if you keep the correct number of teeth on the sector and piston... But if you do want to short stroke it just keep it in mind that a new chip might be needed.

Or can always regrind the chip if you need to. It's easy enough to do if you have a straight edge and some time.

PME is something very different. It's when the gears spin that fast the piston doesn't have time to return fully forwards. The sector tries to pick up the piston as it is still moving forwards and absolutely smashes everything. You don't have any fear of that happening until you start pushing 30 rps, or have other issues that are delaying the piston travel.

This should give you an idea of what needs removing from that chip if you wanted to short stroke the gearbox.

 

[Asomodai]

Just another update on this. 

I switched out the barrel to a ZCI one and chronoed. I immediately had feeding issues. I switched back to the TM barrel and still had issues though not as bad. No idea what happened here. FPS would consistently drop by 200 every non consecutive shot. Apparently a common problem with upgraded P90's. 

It would feed find if I dropped a BB into the hop unit, but not with Mags. 

I opened the gearbox back up. couldn't see anything really wrong, saw that the SHS nozzle had three deep scratches on it, obviously hitting the Hop unit top and bottom, figured the diameter was larger the original nozzle (Or new hop unit has smaller hole). 

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Changed the nozzle out for the Guarder one, still had the same problem, though appears to be slightly better. Tried the Guarder with the King Arms tappet even though it didn't fit, same problem. 

After the 7th time of stripping the gearbox, I used the original tappet and air nozzle, which seems to attach to the tappet plate further up the nozzle and the nozzle is thinner at the top and slightly shorter then the SHS. 

No issues with feeding, no dropped FPS. I changed out the TM barrel for the ZCI. I have a couple of dropped shots when the MAG 170 Round midcap is really full. But seems to be fine after 10 or so shots. During all of this I dremelled out the Lonex Delayer chip and installed that in place of the oversized metal King Arms one. (Because why not!)

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Thinking there was more then one issue here, The ZCI barrel is .03 tighter then the TM barrel, along with the wide nozzle, and slight alignment issues, made things quite bad on semi. The SHS Nozzle was rubbing as it was against the TM quite badly and probably worse with the ZCI. There was slight height differences between the SHS and the original nozzle, the Guarder nozzle is tapered differently to the original as well. 

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Now that I have had to go back to a shorter, non O-Ring air nozzle, the FPS went down from 318FPS to 270 FPS Hop on with the TM barrel. With the ZCI barrel it went back to about 280 FPS hop on. So a bit unhappy that the Air nozzle made such a difference, but at least it appears to feed properly with no drop of the FPS. If push comes to shove I can just upgrade the spring to an M110. The gearbox and motor can take it easily. SHS is 20.8mm and Guarder is 20.7mm, Next tool purchase is for a set of digital callipers to measure the original nozzle and see if I can pick up an o-ringed nozzle of the same length.


Hopefully the anomaly with the mid caps misfeeding when nearly full will go away when the mags are bedded in a bit. 

I am hoping to Skirmish with this next weekend. I am a bit worried as the Hop unit arm appears to apply more pressure on one side of the nub then the other and the rubber appears to be slightly to one side when pressed down. It's not a huge difference, but I am curious if I will have bbs not firing centre. 

 

[Iceni]

Those scratches don't look deep, and they're not all over the nozzle.

Would lead me to suspect the hop unit has a couple of burrs in it. Rather than the nozzle been oversized. The nozzle been metal is a CNC lathe made part. By virtue of its manufacturing process, it should be perfectly round.

You might find the plastic one is even worse over time if it is burrs as it will introduce plastic swarf into the barrel and hop unit.

The best course of action from my perspective would be to polish the hop.

There are a number of ways you can go about it. The easiest is with a drill/dremel and some strips of very very fine wet and dry sandpaper.

Use tape to attach the strip of sandpaper to the shank of a dremel tool, Then wrap the sandpaper round that shank so you end up with a loose cylinder of sandpaper. Pop it in the drill/dremel and run it up and down the nozzle side of the hop unit. You don't want to grind the hop, Just remove any burrs.

In fact, you can see where the sharp edges will be on the hop unit. It's those sharp corners at the very back of the unit where the split is.

 

[Asomodai]

Those scratches don't look deep, and they're not all over the nozzle.

Would lead me to suspect the hop unit has a couple of burrs in it. Rather than the nozzle been oversized. The nozzle been metal is a CNC lathe made part. By virtue of its manufacturing process, it should be perfectly round.

You might find the plastic one is even worse over time if it is burrs as it will introduce plastic swarf into the barrel and hop unit.

The best course of action from my perspective would be to polish the hop.

There are a number of ways you can go about it. The easiest is with a drill/dremel and some strips of very very fine wet and dry sandpaper.

Use tape to attach the strip of sandpaper to the shank of a dremel tool, Then wrap the sandpaper round that shank so you end up with a loose cylinder of sandpaper. Pop it in the drill/dremel and run it up and down the nozzle side of the hop unit. You don't want to grind the hop, Just remove any burrs.

In fact, you can see where the sharp edges will be on the hop unit. It's those sharp corners at the very back of the unit where the split is.

I had thought of this myself earlier. I polished the inside of the hop unit quite well, put the SHS nozzle in. Still got the same problem. In fact it had gotten worse. Constant jamming. 

Tried the Guarder one in and I could at least Chrono it, but again inconsistent FPS by over 200 FPS every other shot. 

So it's still either:

* Incompatible nozzles (considering there are so many different lengths and likely widths in P90 nozzles)

* The aftermarket nozzles moving more side to side in the tappet plate then the original one.

* The hop unit itself just doesn't want to work with the CYMA gearbox very well.

* The pressure of the Midcap mag feeding is causing the hop unit to move down into the receiver which is what's causing the nozzle to lock on top of the hop unit. (Midcap syndrome) http://www.airsoftcanada.com/showthread.php?t=169828

I can confirm that the original nozzle is terrible compression wise which is why the drop in FPS. 

I am at a loss as to my next move, my gearbox screws and P90 backplate screws are getting very rounded opening and closing all the time. 

 

[Asomodai]

Took the gearbox apart again. Put the original air nozzle back in. I poured a bit more silicon oil into the cylinder head to tighten up the seal as best I could considering the crap Air nozzle. 

Managed to get 304FPS with Hop up on full, 330FPS with hop off. So much better now, still leaking a lot of air round the nozzle, but will accept this for better feeding. 

As for the feeding, I reckon it is Mid cap syndrome which could also be putting the nozzle out of alignment more. This time when I put the gearbox together, instead of every other shot dropping FPS, now it would not fire and double feed for the next shot, but only for the first 20-30 shots and not every time. Time to wear these mags in as they are quite new. 

Think I should stop tinkering around with it until it breaks, what do you guys think? Next time I want to deal with this I want a wider selection of P90 nozzles which are a little shorter and narrower if possible, a new gearbox shell as I stripped one of the screw holes for the rear screw and a new set of trigger springs. 

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In some good news, I did another range test today, seems to fire straight and true, so at least I have that!

 

[Iceni]

You are probably right about using it for a bit.

Aug's are just as bad for the air nozzles. All different lengths and widths across all the brands. I think I picked up 2-3 nozzles just so I could get the best fit. Far too many problems once you start to play about looking for perfection.

 

 

[Asomodai]

You are probably right about using it for a bit.

Aug's are just as bad for the air nozzles. All different lengths and widths across all the brands. I think I picked up 2-3 nozzles just so I could get the best fit. Far too many problems once you start to play about looking for perfection.

 

I'll give it one more try with the shortest P90 Air Nozzle, which is the Lonex one. Just ordered one for 5 quid shipped. If that fails, then i'll just go with the original. 

Cheers!

R

 

[Asomodai]

I have installed the Lonex P90 Air Nozzle. 

Although it advertises as shorter then the other nozzles, they are roughly the same size, looks like the Guarder one but with more taper similar to the stock one. 

I am glad to say that it appears to be working better then all of the others. No scratches that I can see. All the other problems appear to be down to midcap syndrome, I am short loading to 150 rounds. The P90 doesn't like .2's it seems when the mag is near full, seems to struggle to feed them. 

FPS is about 335. So it gained another 5 FPS over the stock non O-ring nozzle. 

Will be using this on Sunday and will report back! 

Once I get some cash, I will buy another gearbox shell and trigger assembly. But I guess we can say the project is complete (Again!)

PS. I stuck this on a half charge 11.1v battery and it SINGS. I would rather short stroke it to run 11.1v but it seems to run fine! I'll go with 7.4v initially though! 

 

[Asomodai]

Just had the P90s first skirmish. Was going to only use it for a half day, but my M4s tappet plate was up the creek at chrono, so had to rely on it all day!

Mid cap syndrome is definitely present and I hope the mags will settle down. However the range and accuracy was pretty sterling considering it's humble beginnings! 

I even tried it on 11.1v and it sang for a good hour and a half on that. ROF out performing a TM high cycle by a margin. 

Very happy bunny ?

 

[Asomodai]

Just had the last piece come through the post, the extended EA Buttpad. 

Quite disappointed with this. The rubber is of poor quality. Whilst it does fit, it only adds an addition 2CM length and means I cannot use my Wonderbra sling setup. So probably will go without it. 

Here she is in battle, Tracer unit, Holo and torch installed. Credit to D.B Photography. 

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[Vannmidiron]

Dude I have loved reading the whole adventure you have had. I am going to build something akin to this with a p90. Might try some of it myself but prob lool for a tech to do some also.

 

[Asomodai]

Just did my first true range test with this thing. 

On .30's I was hitting targets at a little over 60 Metres, or over 200 foot. I think that's pretty fair? (Honestly have no idea as I have never gotten actual range number with my airsoft rifles before!)

 

[Davegolf]

That's a good effort and job well done if youve got an effective range of 60M at sub 350

Give yourself a pat on the back for sure, Its nice when the hard work pays off!

Are the midcaps MAG brand?

Ive never had feed issues with those.

 

[Steveocee]

Brilliant read. What a journey.

 

[Asomodai]

That's a good effort and job well done if youve got an effective range of 60M at sub 350

Give yourself a pat on the back for sure, Its nice when the hard work pays off!

Are the midcaps MAG brand?

Ive never had feed issues with those.

Cheers!

The Midcaps are Mag brand. The springs inside them are simply too strong and causes jams until bedded in. This is often discussed on forums. Some say to oil the spring, I am just going to wait until they are used over an extended time. 

 

[Davegolf]

The only time I had grief was if you overloaded them, must have had 12 of them over time.

 

[Crispy1610]

Love this build and it is pretty similar to what I have just done with my gun. However I didnt change the motor or the gears and havent got round to getting the hop up.  I also get the piston stopping in different positions, I think it is when firing in full auto it does it most.

Have you had any trouble with the cut off lever? After putting in the new spring piston set and shimming the gears it totally lost the semi auto, Saw someone recomending to bend the cut off lever up slightly which worked perfectly. However after an evening of playing it kept randomly firing full auto or 3 round bursts before cutting off. I Bent the cut off lever again but this time it snapped so have just bought a replacement and again the gun is working semi auto.
Just wondered if you have had the same problem as it seems to be a common issue with the version 6 gearbox.

 

[Asomodai]

Love this build and it is pretty similar to what I have just done with my gun. However I didnt change the motor or the gears and havent got round to getting the hop up.  I also get the piston stopping in different positions, I think it is when firing in full auto it does it most.

Have you had any trouble with the cut off lever? After putting in the new spring piston set and shimming the gears it totally lost the semi auto, Saw someone recomending to bend the cut off lever up slightly which worked perfectly. However after an evening of playing it kept randomly firing full auto or 3 round bursts before cutting off. I Bent the cut off lever again but this time it snapped so have just bought a replacement and again the gun is working semi auto.
Just wondered if you have had the same problem as it seems to be a common issue with the version 6 gearbox.

Never had an issue with my CO lever to be fair. I am glad I haven't as I would have just chucked everything in the bin if I had another issue! 

Good to look out for though if I come across a spare somewhere. I do need to grab that new gearbox shell soon as well.