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Thread: Please tech my xvalve that's been sitting in a bag for years!

  1. #1
    Join Date
    May 2001
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    Please tech my xvalve that's been sitting in a bag for years!

    Whoa whoa whoa! I've not posted here in a while!

    Anyway, I bought a ULT + Xvalved mag about 6 years ago then stopped playing without ever really using it so it's been sat in a kitbag since then. Now I've started to play again, I dug all my kit out and went about trying to get it to work; I aired the thing up and to my delight it shot and sounded relatively healthy all things considered, however shooting it at anything approaching rapid fire causes it to cough and splutter and over the chrono, the velocity was all over the place, even when shooting very slowly.

    Can you nice chaps help me out any maybe suggest what may be going on?

    Some other stuff that might help:

    * My only HPA bottle is on Guerilla Air Myth which according to the website outputs ~650psi as standard, this sounds a bit low for a mag
    * The RT effect (the pushback on the trigger) was very weak making it extremely easy to shortstroke
    * I put a classic lvl10 mag valve in there which shot just fine, so I'm p confident it's an issue with the xvalve rather than the body/grip/rail
    * I've taken the valve and ULT assemblies apart and they all look correct from what I can see, unfortunately I've either lost (or never had) the parts kits so I've been unable to test stuff out by fiddling with various springs/shims/oring carriers

    Any ideas?

    Cheers!

  2. #2
    Join Date
    Mar 2008
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    Might have something to do with the tank reg. Yeah, it says that it SHOULD put out 650 psi, but depending on a few things, that probably won't happen. I've used a myth reg on my RT Pro valve (same internals as the X-Valve) and it caused some crazy things to happen (full auto, sputtering, etc). I checked the output and it was barely 600 psi. I put on a Max-Flo micro reg on there outputting over 800 psi and the valve worked like a champ. Before you start tweaking the valve, try and get a higher outputting tank on there to see if that helps any issues.

  3. #3
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    You need a higher output reg.

  4. #4
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    I can't get my ULT Xvalve to RT either. I'm using a SHP Ninja tank. I've heard others have had success. My other Xvalve with regular on/off RTs just fine though.

  5. #5
    Join Date
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    Quote Originally Posted by suaze
    I can't get my ULT Xvalve to RT either. I'm using a SHP Ninja tank. I've heard others have had success. My other Xvalve with regular on/off RTs just fine though.
    Take out the ULT.

  6. #6
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    Thanks guys, I'll see about trying it out with a higher pressure.

    Is the reduced RT something to be expected when using ULT?

  7. #7
    Join Date
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    Quote Originally Posted by Jonneh
    Thanks guys, I'll see about trying it out with a higher pressure.

    Is the reduced RT something to be expected when using ULT?
    Taking out the ULT was aimed at Suaze. YOU need a higher output tank. Its the first step.

  8. #8
    And yes, a properly set up ULT is not supposed to RT. That said, if you just keep adding shims to the ULT, you certainly can achieve the RT effect with a ULT on/off.

  9. #9
    Join Date
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    A level 10 mag can operate at around 550psi in the chamber, so 650psi is quite low for pressure. It will have issues with short stroking at anything less than 750psi.
    Except for the Automag in front, its usually the man behind the equipment that counts.

  10. #10
    Join Date
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    Arrow

    THREAD NECROMANCY!

    Thanks for your help chaps, It's been nearly a year and I've finally gotten off my arse and tried a higher output reg but am still having problems.

    First I should say it turns out I don't actually have have ULT, so I'm a doofus. Ignore what I said about that.

    So I bought a ninja SHP reg and bottle initially set to ~1.1k psi which definitely worked and made the trigger react and super bouncy, to the point where it was almost impossible with light fingers not to fire off 2 or 3 shots at a time, I also had a problem where over the chrono the velocity would shoot up sometimes 60-80 fps, even when shooting slowly (maybe 1 shot a second). I figured this was due to the super high pressure so I took the shims out of the Ninja reg which allegedly brings it down to ~900-950psi (I don't have a guage so I can't test), this solved the issue with the super bouncy trigger but I was still having problems with the velocity going up.

    I know the RT/X valve have that issue where when shooting super fast the air can heat up and increase the velocity so you need to fire over the chrono a certain way, I was getting velocity increases while shooting very slowly, both advised when chronoing and normally as I would in a game.

    So is this expected behavior, or (as I suspect) is there something whack with my valve?

    Any help would be appreciated, Cheers!

  11. #11
    Velocity all over the place is a sign of a worn/bad regulator seat o-ring.

    You'll probably be best off to just pick up an X-valve parts kit from AGD or Tuna and do a complete seal replacement. Otherwise, once you chase down one problem you'll just find something else. It's Murphy's Law.

  12. #12
    Join Date
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    If the velocity is higher after it sits for a while than when it has just been fired, then the regulator seat oring is leaking. If the velocity only increases as you shoot, then the problem is due to heating of the air when the valve chamber charges. The greater the pressure differential from input to operating pressure, the greater the shoot-up. So, a higher tank output pressure will increase the amount of shoot-up because it will charge the chamber faster creating more heat. You can create the effect by holding the trigger in before you shoot. By releasing the trigger and then pulling it again, you start with an empty chamber, fill it and then fire before the air cools.

    It really shouldn't be called "shoot-up" for rapid firing. It should be called "cool-down" for waiting to fire. The regulator actually regulates the air to the set value, but the air is hot. When it cools, the pressure goes down. If we check the velocity when the air is hot, the velocity is at its highest value. If we check the velocity after the air cools, the lower pressure gives us a low velocity reading. If we could somehow maintain the temperature of the valve at a hotter value or keep the air from heating, the velocity would not be different from rapid firing or sitting and waiting.

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