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Thread: Xvalves... velocity won't come down (or really change at all)

  1. #1
    Join Date
    Sep 2016
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    Austin, TX
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    Xvalves... velocity won't come down (or really change at all)

    Got a tech at my local field who calls me when he gets mags in...

    Guy brought in a couple of guns with xvalves... Scott told me when he aired one up it vented out the back and blew a bunch of old lube and crap out of the velocity hole...

    When I read that I thought "bad piston"... we oiled the gun and lubed the springs in the back of the valve... and the next time we aired it up there was no venting...

    But then we took it to the chrono... and no matter how far in or out we adjusted the velocity... it stayed at 325. This was with a standard input tank (800 PSI)... it was maybe 100 degrees out...

    I was thinking maybe the piston wasn't ruined/worn out enough to leak... but that maybe it was still not quite right and was effecting the velocity... I just can't wrap my brain around what was going on... the air chamber should be increasing or decreasing as we change the velocity screw... so how it velocity not changing?

    Let me know thoughts.

    Thanks.

    Armando

  2. #2
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    is the piston sticking on the pin?

  3. #3
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    Check the reg seat, if there is anything on it, then it will do as you described. Since it blew crap out then it needs a good cleaning, anyway

  4. #4
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    Sep 2016
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    Quote Originally Posted by vintage View Post
    is the piston sticking on the pin?
    I didn't think to check that... it would make sense though that the piston isn't moving when we tighten or loosen the velocity screw... I'll take a look wednesday.

    Thanks!

  5. #5
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    Quote Originally Posted by Nobody View Post
    Check the reg seat, if there is anything on it, then it will do as you described. Since it blew crap out then it needs a good cleaning, anyway
    When you say reg seat... on the xvalve there is a small o ring where the reg seat would be on a classic... if you are referring to that o ring... we had replaced it prior to checking velocity... so the assumption is it was clean... but I'll check it.

    Thanks!!

  6. #6
    Did you get this issue worked out? Sounds like you checked everything but the regulator pin assembly itself. If the pin is not intact, oring worn or bad, possibly it is assembled incorrectly. Sometimes the c-clip falls off. Some versions were made with a much weaker c-clip and could come off. Make sure that assembly is correctly assembled with 2 fresh #779 orings. You can re-use the nylon spacer, and make sure the spring stack is like this ()()()()().

    If the reg piston is bad the gun vents and will start at lower than shooting velocity. A bad piston will not make the gun shoot 325fps. The piston venting is what is supposed to stop the gun from shooting 325fps.
    A bad regulator pin assembly will make the gun shoot hot.
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  7. #7
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    And make sure you are chronoing it correctly. Do not chrono like other guns or your reading will be way off.
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  8. #8
    Join Date
    Sep 2016
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    Austin, TX
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    Thanks Guys.

    Haven't connected with Scott lately... going to see him tonight and we will see what is up with that gun.

    I'm going to bring the guido and we'll compare the two.

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