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FX Impact Mk 1. Regulator Problem.

Brooksy

Brooksy

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@cloverleaf and all.
A mate has dropped off his Impact Mk 1 with me. It won't fire even though it's full of air. A quick check revealed a regulator pressure of 150 bar, so, the seals are shot and the pressure is too high for the valve spring to overcome. As I drained the air down, it fired, so that's the issue.
Adjusting the reg pressure by screwing it in, then back out made no difference to the pressure reading.
Any of you with an Impact, sub 12 in .177? Can you have a look at your secondary reg gauge please and let me know what it's set to? My mate recalls something between 40 and 60 bar.
Thanks in advance.
 
If I were you, I'd start by replacing the two adjustment screw o-rings, the innermost one will give that symptom as well as a bad sealing face, the o-rings on the MK1s I fix have gone really brittle, and if you remove the whole reg to play and damage the internal C39, it's a real nightmare to replace especially on a mk1 with only a 8mm hole. It might give you some breathing space before needing a complete o-ring replacement.
the 2 C38's are 2x1 NBR 90

ps If anyone has found a tool or any way to simplify the replacement of the dreaded C39 o-ring, please share
 
Last edited:
APT said:
If I were you, I'd start by replacing the two adjustment screw o-rings, the innermost one will give that symptom as well as a bad sealing face, the o-rings on the MK1s I fix have gone really brittle, and if you remove the whole reg to play and damage the internal C39, it's a real nightmare to replace especially on a mk1 with only a 8mm hole. It might give you some breathing space before needing a complete o-ring replacement.
the 2 C38's are 2x1 NBR 90

ps If anyone has found a tool or any way to simplify the replacement of the dreaded C39 o-ring, please share
Click to expand...
I use a plastic pick to get C39 out and then wing it with a wooden kebab skewer with the end sanded flat to fit a new one , I have the 8mm reg , do you know if the reg body is available anywhere as I'd like a spare just in case ? Remachining a 10mm body is an option but a new part would be nice to have !
 
Sounds like the reg is letting by so the valve is seeing a much higher pressure than it would if the reg was working and the hammer spring set as it is isn't strong enough to knock the valve open .
 
Good detective work @Brooksy - I don't have any pressure data to hand but it seems like others have seen you right :)

APT said:
If I were you, I'd start by replacing the two adjustment screw o-rings, the innermost one will give that symptom as well as a bad sealing face, the o-rings on the MK1s I fix have gone really brittle, and if you remove the whole reg to play and damage the internal C39, it's a real nightmare to replace especially on a mk1 with only a 8mm hole. It might give you some breathing space before needing a complete o-ring replacement.
the 2 C38's are 2x1 NBR 90

ps If anyone has found a tool or any way to simplify the replacement of the dreaded C39 o-ring, please share
Click to expand...
It's a terrible design, isn't it? Not just from the perspective of physically getting the seal out, but more-so the potential to damage the block whilst attempting to do so.

Also I don't see why it needs to be a 90 shore item - which typically don't last as long, tend to crack and come out in bits and of course are a lot more difficult to manouver in / out.
 
Sharpsman said:
Sounds like the reg is letting by so the valve is seeing a much higher pressure than it would if the reg was working and the hammer spring set as it is isn't strong enough to knock the valve open .
Click to expand...
That's what I concluded. I've ordered the O ring set from Bagnall and Kirkwood, then, I'll take it apart and have a look.
 
Brooksy said:
@oneshot , O rings arrived today, but, Mrs B wants to go away in the motorhome, so, we've booked mid Wales. I'll strip it down middle of next week mate.
Click to expand...
If you go back to Wales check this place out , lovely site , spotless loos and showers and no kids !!
Screenshot_2025-09-25-19-32-25-097_com.google.android.googlequicksearchbox.webp
 
Brooksy said:
@oneshot , O rings arrived today, but, Mrs B wants to go away in the motorhome, so, we've booked mid Wales. I'll strip it down middle of next week mate.
Click to expand...

Take the gun with you. It's mid-Wales. They didn't build all the reservoirs there because they stuck pins in a map. It'll rain all the time you are there, so you'll need something to do. 🤣
 
I just rebuilt mine the other day, I also replaced “the dreaded c39 o-ring” honestly though it took me about 3-4mins to replace it, it really wasn’t that hard at all & I’m not an expert or anything. I recommend a nice set of picks small enough for the 8mm hole & a head torch for good visibility in the hole 👍

Also measure the piston once removed if it’s 14mm long you need a gen 1 replacement, if it’s 16mm long you need a gen 2 replacement, a gen 3 uses the same piston but is wider than the gen 2 so won’t physically fit. Don’t trust the serial number check, physical measure the piston as my fx is an early version with an old serial which places like B&G will say is the gen1 but it’s not, mines the gen2 16mm piston.

Best of luck 🤞
 
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