Is my FX Maverick front regulator toast?

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the_phew

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Oct 11, 2021
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VA, United States
My .25 Maverick Sniper had been shooting fine, but the other day the FPS was all over the place (like +/- 75 fps) and I'm pretty sure I no longer heard the plenum fill up between shots. I had never touched the regulator pressures since I've owned the gun, just swapping in the heavy slug liner and the 'Slug Power Kit'. Rear reg was set at like 110 bar from Utah Airguns, front reg shows like 135 bar right now. The bottle is at 200 bar. I was going to increase the front reg pressure, but in every video about Maverick tuning, there is an audible hiss after just like a quarter turn CCW of the front reg screw; I was up to at least 4 turns CCW without a single sound, and the reg gauge never budged from 135 bar (yes, the brass set screw that bypasses the rear reg is open/flush with housing for this step).

Is the reg pressure not changing in response to turning the front reg screw CCW an indication of a failed front regulator? Or something else? Should I keep turning the front reg screw CCW until something happens? It's not obvious how deep the front reg set screw is in its housing; it's buried down there.

Thanks
 
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that would be too far out on my regs and I am sure they are all very similar. What usually happens is you shear the upper O-ring on the stem. If you de-gas the gun and back the stem all the way out t will look like there are 3 O-rings on the stem. There is only supposed to be 2 the furtherest up is what got sheared off. When I made the same mistake on my 2nd reg it leaked air out the top of the reg.
You can get the O-rings through an FX dealer or FX USA. They take some patience t change but easy enough to do.
 
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Chukar60 said:
that would be too far out on my regs and I am sure they are all very similar. What usually happens is you shear the upper O-ring on the stem. If you de-gas the gun and back the stem all the way out t will look like there are 3 O-rings on the stem. There is only supposed to be 2 the furtherest up is what got sheared off. When I made the same mistake on my 2nd reg it leaked air out the top of the reg.
You can get the O-rings through an FX dealer or FX USA. They take some patience t change but easy enough to do.
Click to expand...
Be that as it may, it doesn't explain why turning the front reg stem CCW did not increase the regulator pressure at all.

To reiterate:
1. Gun was behaving erratically
2. I decided to check/adjust front regulator pressure
3. With rear regulator stem open/flush, gauge read 135 bar (bottle was at 200 bar)
4. Backing out the front reg stem had no effect (no hiss, no change in indicated pressure)

Neither regulator had been touched until today.

EDIT-The front regulator stem passed the 'soap bubble test', so I guess the O-rings are fine. That's little solace though, since it does seem that the regulator itself is dead.
 
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I was not addressing your original post, just the front reg and the possibility that it had been damaged by backing it out too far while under pressure.
What you described in your original post is beyond my skill level to assess correctly.
I would suggest calling FX USA (1-866-639-0772) Their techs have been very helpful for me.
 
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FX support says I "Need to add Belleville washer to the stack inside the regulator to increase the pressure" of the front regulator above 135 bar. I'm not specifically after higher pressure (the gun was slinging 34.9 gr NSA slugs at any speed I wanted with low ES), I just wanted to make sure the regulator was working properly, so I don't think I'll pursue this step.

I did notice my hammer adjustment screw was all the way in (which I didn't remember doing?), which seems non-ideal from other Maverick tuning threads. So I'll back that out (6mm?) and give it another shot.
 
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I've got exactly the same issue. As a note and in my defense, I've worked with o-rings and mechanical things for more than a few decades.

1. Carefully backed out the #2 reg to flush plus a wee bit, checked the pressure 137 bar.
2. This is where I got creative...removed the bottle completely, dry fired the gun a few times until the air bleed out entirely,
3. Screwed in the #1 reg until very slight resistance and back it off 1/2 turn.
4. Started backing off the #1 reg. checking the pressure and....next to butt-kiss.
5. Kept backing it out until air started leaking out the #1, yep, not a good thing.
6. Repeat #2
7. Screwed in the #1, reattached the bottle, and 11.3 bar all the way until the reg started leaking.
8. Removed the bottle and bled the system.
9. Removed the WTH
10. Removed the reg.
11. Removed the adjusting screw
12. Mild cursing as the top o-ring was absolutely shredded. WTF I'm 99.873% certain it wasn't me.

Looks like a call to FX on Monday, because I've zero idea how to tear that reg apart or what size the o-ring is...and I'm moderately certain that ACE hardware doesn't have one.

Now the FYI, I was running about 106 Bar on the rear but the SD was pretty bad, so I wanted to do a bit of a tune. Note to self....don't F with something that works....I NEVER LEARN.

Edit....Ok this is weird, there are only TWO o-rings on the adjustment screw according to the FX schematic, so...why in the H is there the shredded one when the other two are looking pristine?

And where in the H are the Belleville washers? I don't see a darn thing and the schematics don't show a darn thing.

Edit, ahhhhh found the little suckers, thanks to a video, they are at the bottom of the hole on a pin, you get them out with a tool the guy sells or a hemostat works great.

Edit. found the bad o-ring, on the top of the adjustment screw, it's a 2x1 90 just lightly shaved off, gut feeling it was bad and when I made the adjustment it let go. Ordered a kit From Amazon, Capt. O-ring, faster than mucking with the dealer.
 
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the_phew said:
FX support says I "Need to add Belleville washer to the stack inside the regulator to increase the pressure" of the front regulator above 135 bar. I'm not specifically after higher pressure (the gun was slinging 34.9 gr NSA slugs at any speed I wanted with low ES), I just wanted to make sure the regulator was working properly, so I don't think I'll pursue this step.

I did notice my hammer adjustment screw was all the way in (which I didn't remember doing?), which seems non-ideal from other Maverick tuning threads. So I'll back that out (6mm?) and give it another shot.
Click to expand...
Your Maverick should handle 34.9 NSA no problem with minor reg adjustments. If it is not, it's more than likely a reg problem. O-ring or a nicked piston could do it. Keep the micro grub closer to 4.5-5mm if you can for shot count.

Patrick
 
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Every step I take trying to debug this seems to break something new. After shredding an O-ring on the front regulator stem, I replaced that. Took both regulators apart and didn't see any damage to O-rings or piston. I switched both gauges to Huma 23mm units, because the error-prone FX gauges complicated the process.

I nearly-closed the front regulator and re-attached the bottle, but now there is a slight hiss (around the bottle it seems; both regulator stems pass the 'soap bubble test'). When I remove the bottle, all the air in the plenum leaks back out through the bottle nipple (rather quickly; took less than a minute to drain back out). I assume there is a check valve that normally prevents this from happening? Or are the regulators supposed to inherently prevent backflow? Could I have re-assembled the front regulator in some incorrect way that allows backflow?

FYI, all of this was happening with the bottle at only 50 bar; but I'm loathe to add air to a system that's clearly not operating correctly.

This is a very frustrating process; I can't even debug my original issue since at least two other things have broken while trying to debug the original issue.
 
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Well, I can't add air because it leaks faster than I can pump; I have a compressed air tank, but it's 100 miles away right now. I soap bubble tested all around the bottle, fill probe, reg stem, gauge, etc. and didn't find any visible leaks, so it must be leaking through the chamber? Removing the bottle still allows all the air in the plenum to quickly blow back through the bottle nipple; I assume there is a check valve there that is not working.

I read another thread where an FX Boss owner needed to cock the rifle to fill it, but that didn't help this issue (although maybe filling with compressed air would work).

Can an FX Maverick only be refilled from empty with a compressed air source (not a hand pump)? Or am I missing something?
 
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I chambered a pellet (even put some silicone grease around the skirt), but the rifle is still leaking at least 5bar/min by the time the bottle is up to 50bar. And at that point the Hill foot pump is too hot to touch, so I literally can't keep up with the leak without destroying the seals in my pump.

Another thread indicated the culprit may be this O-ring:
1661384463012.png

So I tore my rifle down to check, but that O-ring is in pristine condition. So that's not it.
 
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Repeatedly blasting the bottle full from a compressed air tank eventually shut whatever valve was stuck open, so at least it's not leaking anymore. The moral of the story there is don't disassemble an FX airgun unless you have a high pressure air tank to refill it afterwards. Which is pretty dumb in my opinion; surely there are many airgunners that solely rely on a manual pump.

I haven't had a chance to shoot or tune it since fixing the leak, so I don't know if my original issues persist. The whole debugging-->leak-->inability to refill experience was so infuriating that I'm considering just giving up the hobby. The function of modern PCPs is seemingly over-dependent on the whims of rubber O-rings, silicone grease, and threadlocking every friggin' screw. Then again, my rimfire experiences haven't been much better, so pick your poison. If I had a dollar for every time my brand new S&W Model 41 stovepiped when 100% clean+lubricated and using the factory-recommended CCI SV ammo, I could buy a whole collection of airguns.

I'll update in a couple weeks when I get a chance to shoot again.
 
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OK, I spent the afternoon yesterday tuning. With the front reg at 150 bar and the rear reg at 120 bar, it was slinging 34.9gr NSA slugs at 960fps. Shooting at a KYL rack at 50 yards, I hit the 0.5" spinner five times in a row once (just off a bipod with no rear bag, and I'm a poor shot). So accuracy is good.

The only hangup is that this was with the power wheel at 1 and the hammer spring adjustment screw all the way in. Increasing the power wheel only lowered the velocity. I'm guessing this means I shouldn't be using the heavier hammer spring weight from the slug power kit, so I'll switch back to the original hammer spring weight and see if that makes the power wheel useful again.

I believe the root of all my original issues were the crappy OEM gauges. Tuning went exactly like it should once the indicated regulator pressures actually made sense.
 
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the_phew said:
OK, I spent the afternoon yesterday tuning. With the front reg at 150 bar and the rear reg at 120 bar, it was slinging 34.9gr NSA slugs at 960fps. Shooting at a KYL rack at 50 yards, I hit the 0.5" spinner five times in a row once (just off a bipod with no rear bag, and I'm a poor shot). So accuracy is good.

The only hangup is that this was with the power wheel at 1 and the hammer spring adjustment screw all the way in. Increasing the power wheel only lowered the velocity. I'm guessing this means I shouldn't be using the heavier hammer spring weight from the slug power kit, so I'll switch back to the original hammer spring weight and see if that makes the power wheel useful again.

I believe the root of all my original issues were the crappy OEM gauges. Tuning went exactly like it should once the indicated regulator pressures actually made sense.
Click to expand...
This should solve your problem. The factory setup has plenty of power for 34rg without stressing the system. Set the HS grub out to about 3mm as a start point. Work the PW to get back to your 960 before the knee of power curve. Enjoy.

Patrick
 
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