Tuning BRK Ghost .22 HP not producing power any suggestions?

[robertwalsh1981]

I have been tinkering with my Ghost, swapped springs out for the White spring and then Blue spring, and testing different reg pressures and now it is only able to achieve ~620 FPS with the following configuration.

BRK Ghost .22 HP
23" barrel
Red Hammer Spring
Tank ~190 BAR
Reg ~165 BAR
PW Max
JSB Exact RS Diablo 13.43 gr.
FPS = 622 (highest)

When it first arrived it was cranking the JSB Hades 15.89 gr pellets at close to 1030 FPS with the following configuration:

BRK Ghost .22 HP
23" barrel
Red Hammer Spring
Tank ~190 BAR
Reg ~150 BAR
PW Min
JSB Exact RS Diablo 15.89 gr.
FPS = 1030

I am charging it from a Yong Heng compressor with this secondary water/oil separator in line between the compressor and the gun.


I should also mention that when degassing the gun it is taking 15+ shots with the PW on MAX setting before the reg pressure drops below 50 BAR, not sure if this is relevant, but from my limited experience/knowledge it seems to indicate that perhaps the valve is not opening fully?

Any thoughts or suggestions on what might cause this behavior?

 

[Franklink]

Your "valve pin" (valve stem) will need to be tightened so that the head is supported by the flared piece with the white oring. If it won't screw together, take it apart and clean it well and make sure none of the threads are damaged or cross threaded. You'll need to to Loktite it on final assembly. I don't think Red Loktite would hurt... you'll not want it to come apart, maybe ever...
Bob

I agree. I've not seen the valve stem unthreaded in any of the 4-5 valves that I've been inside....

 

[greenbeans]

I agree. I've not seen the valve stem unthreaded in any of the 4-5 valves that I've been inside....
View attachment 531201

You found your problem. This made the valve/pin too long, can’t open fully. Screw it in (put vibra tite on it if you have it (I wouldn’t use locktite) and out it back in, you should be fine! Weird how that happened though…

 

[robertwalsh1981]

You found your problem. This made the valve/pin too long, can’t open fully. Screw it in (put vibra tite on it if you have it (I wouldn’t use locktite) and out it back in, you should be fine! Weird how that happened though…

Yeah, I cleaning the male threads with a brass wire brush, but it isn't wanting to thread in any further. It acts like the threads are galled. So I am going through my tap/die set to see if I have anything that matches the threads in hopes of cleaning them up (gently) by hand.

 

[Franklink]

I would expect this to be a warranty coverage item.

If not, I've seen Ghost valve stems for something like $20 from one of the UK parts suppliers. Of course tack on some shipping. If you don't have warranty, a stand-alone valve stem would be much cheaper than an entire valve.

 

[robertwalsh1981]

I would expect this to be a warranty coverage item.

If not, I've seen Ghost valve stems for something like $20 from one of the UK parts suppliers. Of course tack on some shipping. If you don't have warranty, a stand-alone valve stem would be much cheaper than an entire valve.

Yeah, I have reached out to Tony at Talon Airguns to see what the process for a warranty claim looks like. The complete valve is ~$150 from AOA so if the warranty doesn't work out I will be digging online in search of a replacement stem.

 

[greenbeans]

Yeah, I have reached out to Tony at Talon Airguns to see what the process for a warranty claim looks like. The complete valve is ~$150 from AOA so if the warranty doesn't work out I will be digging online in search of a replacement stem.

If you got it from Tony he’ll make it right!

 

[robertwalsh1981]

With a bunch of elbow grease and about an hours worth of threading the stem pieces back and forth/back and forth, I was able to get them seated. They now have a dose of Loctite (I only had the blue, but it is better than nothing) and the gun is reassembled. I took it out right at dark to confirm FPS with:

Blue Spring
Reg ~150 BAR (was aiming for 140 oops)
PW Min
JSB Exact RS Diablo 13.43 gr.

- Chrono missed the shot, but a super sonic crack never sounded so good!

I switched over to the JSB Hades 15.89gr

Shot 1 - 1,058 FPS
Shot 2 - 1,086 FPS
Shot 3 - 1,086 FPS
Shot 4 - 1,088 FPS
Shot 5 - 1,090 FPS

Thank you all for the suggestions and help!

 

[Franklink]

Hot dang! Back in business.

Way too fast for that pellet but your power potential is back for sure.

 

[robertwalsh1981]

Hot dang! Back in business.

Way too fast for that pellet but your power potential is back for sure.

Yeah, going to have to degas the gun again to get the reg down a bit and see how they do. Ideally I want to see if I can get it dialed into a tune like the one HERE
======
.22 HP 23 inch barrel, reg 152ish (damn baby gauges…), blue spring:
AEA 25.3gr at 950fps on PW 16
AEA 21.9gr at 915fps on PW7
Hades 15.89gr at 940fps on MIN (they’re surprisingly accurate at that speed).
======

That would let me shoot both the JSB Hades 15.89 gr and the Hades Monster 25.39 gr pellets as I would be using the lighter pellets from 10-50 yards and the heavier pellets from 50-100 yards on targets and ground squirrels.

 

[robertwalsh1981]

It doesn't sound like it is very common but I thought it might be worth sharing what was happening and a summary of the solution incase someone else ever runs across it.

:::::Issue:::::
A few days ago my new Ghost suddenly stopped producing power it would shoot but instead of getting ~850 - 900 FPS it was now struggling to get ~620 fps with the following configuration.

BRK Ghost .22 HP
23" barrel
Red Hammer Spring (Factory HP spring)
Tank ~190 BAR
Reg ~165 BAR (the reg was this high as I had begun troubleshooting and had been slowly increasing it to see if FPS would climb, it didn't)
PW Max
JSB Exact RS Diablo 13.43 gr.
FPS = 622 (highest)

This behavior began while I was fiddling with various tunes and had degassed the gun several times following the procedure (dry firing) outlined in the BRK tutorial video HERE to degas the gun.

Verified the following:
- Transfer port correctly aligned
- Probe O-ring was in place/intact (and lubed)
- Pellet debris not blocking hammer/spring
- Hammer was not damaged
- Increased reg pressure
- Plenty of air in the tank

:::::Solution:::::
I found that the internal tip of the valve stem (end opposite of the poppet) had come unscrewed and was restricting the travel of the valve stem.

It should look like this:

The shortcut to identifying this was:
1. Degassing the gun (I would avoid dry firing as I believe that is what caused this issue)
2. Removing the rear of the gun to expose the valve poppet
3. With the gun fully degassed (Reg gauge reading 0) see if the poppet moves when you press on it (it should move freely like in the video).

If it does not move, or only moves slightly you will need to pull the valve. I followed the steps outlined in the BRK Ghost Strip Down Tutorial and used a pair of snap ring pliers with changeable tips.

As I was pulling the valve out of the gun I noticed that there was almost no flex in the valve assembly unlike what we see HERE and it took quite a bit of effort to get the two halves of the valve body to separate.

When attempting to tighten the two halves of the valve pin it acted like the threads were galled and would not tighten, I was able to unthread the two halves of the valve stem and then cleaned up the threads as much as possible with a brass wire brush. Then I worked at threading them together working them back and forth/back and forth until I was able to get them almost tight (maybe a 1/16" gap) at which point I wrapped the poppet end of the stem in a towel and "clamped" it with a vice grip which allowed me to use a crescent wrench to finish tightening up the halves.

In the end I took it back apart, cleaned the threads and applied some Loctite to ensure that this will not happen again. After reassembling the rifle I tested it with the following configuration and results.

BRK Ghost .22 HP
23" barrel
Blue Spring
Reg ~150 BAR (was aiming for 140 oops)
PW Min
JSB Exact RS Diablo 13.43 gr.

- Chrono missed the shot, but a super sonic crack never sounded so good!

I switched over to the JSB Hades 15.89gr

Shot 1 - 1,058 FPS
Shot 2 - 1,086 FPS
Shot 3 - 1,086 FPS
Shot 4 - 1,088 FPS
Shot 5 - 1,090 FPS

I am leaning towards the theory that my degassing via dry firing (I was doing a LOT of this) while tweaking my tunes ended up causing this issue. So moving forward I will be degassing via cracking the manometer.

I hope this info can help the next person that runs across this issue.

Again many thanks to @Franklink and @greenbeans for responding to all of my questions all of the suggestions.