Tuning FX M3 reg issues

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R

R0B

Member
Apr 14, 2021
202
125
Yorkshire, United Kingdom
I decided to upgrade my MK2 impact to M3 spec. I have bought the necessary parts and installed everything, including a Huma reg. For weeks I have been having an issue with the reg (low pressure version) dropping lower and lower with every shot. If I then leave it for 10 minutes, it will re-fill to the set pressure. I have stripped it and rebuilt the reg numerous times including new seals. I have even replaced the reg with new unit to no avail. It's been suggested that the first reg might be faulty, but I have even swapped that over with a friends. I have run out of ideas, and will probably have to send it to a professional if I cant sort it out. That is really frustrating, as I'm pretty good with PCPs and have never been beaten (yet). I was wondering if anyone has any suggestions?.

Thanks 

Rob
 
You need to step backward through your changes to isolate the problem. If you changed a factory part out for aftermarket, reinstall the factory one, then remove any parts added that weren't there before (ex: bottle reg), etc. All this being done one part at a time, and then checking.

One potential cause that isn't part failure related, is a blockage in one of the gun's internal passageways. On the M3, there is a grub screw that seals off the passageway for the angled manometer bracket, and sometimes the factory puts a small chunk of oring under it to seal. That oring chunk got sucked into the internal plumbing on my M3 downstream of the second reg and really screwed with plenum fill times. Keep in mind that grub screw is specific to the M3, and won't be applicable to your M2, but you'd see a similar effect if debris got into the passageways.

You have an airflow problem of some sort whether in a passageway, a passageway inside one of the regs, or the reg itself being unresponsive and choking off flow. You just have to methodically narrow it down.
 
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I agree with TDK. Using Teflon tape on threaded parts that doesn’t need it can clog up systems when a tail piece of Teflon comes loose.

find the tiniest bristle of a wire brush and run that thru the pinhole passageways of the reg piston and adjustment screw. You may have a tiny blockage there also.

to the OP- you never stated what the 2nd reg pressure is set at. 
 
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Firstly, thanks for all the replioes and input.

Ist reg is set from factory at 140 BAR

the information on the M3 passageways being blocked might be a very good point. When I was assembling the M3, the dog point grub screw that is used to seal the hole for the manometer bracket wouldn't seal. I saw a couple of posts on tghe internet about using a slice of 2.5mm 'O' ring to seal it, which is what I did. On reading the suggestions aboive, that would make perfect sense. I will find a suitable brush and attempt make sure the passages are clear. Can anyone suggest how the hole should be sealed?.

As for the parts changed, I have bought everything that was different between the MK2 and M3, so have not attempted a hybrid.

Thanks

Rob
 
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What do you mean you upgrade your mk2 to the m3 and now have dual reg. The mk2 can't not be upgrade to the m3. None of the parts are compatible. Only thing you can upgrade is just the 72 plenum and change the power wheel. That's it. I'm guessing you just bought a bottle reg and sit in front of the bottle. Thats different from the m3 reg. Its more like a reg you see on a paintball gun bottle. How about removing it and just screw back the bottle and see if it is actually the fx reg under the trigger. 
 
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I don't know if you can brush those gun passageways - small, oddly shaped, and hard to access. What I did was remove the second/back reg, then I pulled the rear plenum gauge and installed a foster QD in that spot. I then CAREFULLY back-flushed the plumbing with air from my fill tank. I did NOT slam it with 310 bar air, but CAREFULLY used a tank with lower pressure and cracked the valve slowly until the oring chunk shot out into the paper towel I had taped over the second reg hole. My situation was a bit clearer since I could see part of the oring chunk peeking out of the passageway behind the second reg.

if you are checking out the tiny passageway in the reg piston, then you can use a single wire brush bristle like Bigragu said, and also use low pressure shop air (~140psi)

I want to stress having a calm head and analyzing the results you get with each step. Don't just start swapping out parts without a plan.
 
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I think it is likely to be the 'o' ring section that I used to seal the grub screw for the manometer bracket. I removed the grub screw and screwed the bottle on (which gave 140 BAR), the 'o' ring section wouldn't move, so I removed the pressure and slackened the 2nd reg slightly and then screwed the bottle back in. The section of 'o' ring blew out of the hole. I think I will now likely blow out all of the holes as you have kindly described. I couild still do with some guidance as to how to seal the grub screw for the manometer bracket air hole. In all honesty I have a busy few days, so it might be the early part of next week before I can update the thread.
 
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This is one of those points of "analyze each step and act accordingly". It sounds like the oring section was indeed wedged at least partly into the internal section of the gun with how you described it. With a potential cause fixed, it makes the most sense to re-seal the grub screw hole and test before doing anything else. If you do further disassembly to blow out other passageways, that may unnecessary and you are only introducing more possible issues. Test before moving on.

With regard to sealing the grub screw hole, I can't really help as I went straight to the angled manometer bracket. I have considered trying a slice of a 90A oring if I ever revert, though. The thought being that the harder rubber would resist being pushed/sucked into the wrong side.
 
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