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Fx Crown Leak

Discussion in 'Technical' started by luap, May 20, 2020.

  1. luap

    luap Donator

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    hi i was asked to look at the seals on a fx crown its leaking straight down the barrel when you fill it i have looked it up an from what i could find it should be the seal around the outside of valve seat i have changed the Oring and polished the seat it still leaks tried filling with it cocked .I believe the leak started after the owner fitted new washers in the reg ?

    just to add it does not have (D39or D38)spring seat or Oring but the end cap does not have a hole rite throw it so i wondered if this was a newer version than the picture as i had read it would be this Oring if air came out the hole in the it does not have
    any advice appreciated thanks paul
     
    Last edited: May 21, 2020
  2. Spray1Mark

    Spray1Mark Major Poster

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    Whats the serial number?
     
  3. luap

    luap Donator

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    184194
     
  4. Chocki

    Chocki Engaging Member

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    Have you got a full bottle that fits on the gun to hand, it may require a high pressure behind the valve to seal it shut and filling slowly will not be enough to build up enough air pressure behind the valve to shut it.
    My dreamline when I emptied the gun of air complately did exactly the same, screwed a full bottle on and the valve instantly sealed and has no issues.
    I just make sure before doing any work on the gun which involved depressurising it, I have a filled bottle to hand ready to screw onto the gun.
     
    luap likes this.
  5. v1ktor

    v1ktor Busy Member

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    I had a similar problem with my FX Bobcat Mk1.

    Air would leak directly down the barrel as it was being filled.

    I tried lapping the valve and seat to provide a seal, unfortunately without success.

    I finally replaced the seat and valvepin to stop the leak.

    I do not recall the valvehouse having a hole all the way through it.

    It definitely had the O ring but no spring seat - it has both now.

    I do remember from one of Ernest Rowe's video he mentioned the damage done to valve and seat if the gun is fired empty or with very little air pressure.

    HTH
     
    luap likes this.
  6. luap

    luap Donator

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    he has a valve ordered for it an i have ordered a new seat for the valve an spring seat i was wondering if it could of been that it should have the valve spring seat to make enough pressure on the seat for it to seal i think it was Ernest Rowes video that was saying if the Oring on the spring seat was leaking it comes out a hole in the end
    the air comes out slower than it goes in so if i left it filling for a while it may build up enough pressure and seal ?
     
  7. v1ktor

    v1ktor Busy Member

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    Yes, either it leaks via the valve/seat or the valvepin housing/guide thingy.
     
    luap likes this.
  8. luap

    luap Donator

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    well its had a new seat new valve new rod in regulator i noticed the reg gauge does not move it still leaks down the barrel i cant fill the bottle when its off the rifle and i dont know any one with a full bottle to try
    any ideas i have had it conected to the dive bottle full open no change
     
  9. neiled

    neiled Donator

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    I had a similar problem on my Impact of the valve not seating causing a leak through the transfer port and on down the barrel but I'm not sure if this would help on a Crown. Even with the leak it still allowed me to slowly fill the bottle to 250BAR although it did take longer and wasted a fair bit of air.

    With the bottle off the rifle and the safety on, I adjusted the reg for higher pressure (anti-clockwise), pulled the cocking handle back and screwed the bottle on. There was still a slight leak but after cocking and firing a few time it stopped as the valve seated and sealed. I then adjusted the reg pressure down to where I wanted it.

    Note: My Impact does have the AMP reg fitted which can be adjusted downwards whilst pressurised.
     
    luap likes this.
  10. luap

    luap Donator

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    i tried what you have said in the first part but have not adjusted the reg i set the reg 1 full turn in from flush
    when i fitted the new rod.
    i was expecting a bang when fired but i dont think the hiss changed i found a bit odd i have even tried with out the Oring on the valve pin so it would have on restriction incase it was to stiff i know it would leek out the hole whilst firing but just for test may have helped
     
  11. John Entwistle

    John Entwistle Busy Member

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    Is this sub 12 or FAC if it’s sub 12 then you need the remove cylinder, degas, screw the reg all the way in then out about 1 turn and try again, reg pressure of 60/70 should be fine to tune it in to a safe legal tune. If it’s FAC then watch this
    He is FX master tuner in the us
     
    luap likes this.
  12. luap

    luap Donator

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    ok thanks i was going for high reg pressure to seat the valve i did think it would run at about 90-110 bar sub 12 i didnt realise they ran so low i was going to get it working and turn down i didnt realise you need to be low and go up ,i was trying to keep the tip away from the regulator rod as i think someone had wound it in and damaged the tip that was why i replaced it
     
  13. Tim_B

    Tim_B Pro Poster

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    My Crown runs at 110bar, sub 12. having said that it is an early version which needs a slightly higher pressure - I would say 85 to 95bar would be spot on, sub 12.
     
    Jeffsky and luap like this.
  14. neiled

    neiled Donator

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    My new sub 12 .177 cal Crown Compact (Continuum) is running at 80BAR.
     
    Jeffsky, Tim_B and luap like this.
  15. Chocki

    Chocki Engaging Member

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    Was this for an FAC rifle?, these have a much higher force on the hammer weight to overcome the much higher regulator pressure, so yes, with no pressure behind the valve your going to smack the hell out of the valve pin when dry fired. Although not recommended, our sub 12 guns are less likely to get damaged.
     
    luap likes this.
  16. Jeffsky

    Jeffsky Busy Member

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    The standard crown was being shipped with the reg set 50/60 bar, the continuum/ compact 80/90 bar and as Tim says the early crowns had a different reg so set 100/110 bar :thumb:
     
  17. luap

    luap Donator

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    ok thanks we are trying to sort the bottle out as it leeks above 60 bar when not on rifle an then going to try and get an adaptor to fill the bottle so i can screw on a full bottle see if it makes any difference to being connected to the diving bottle its all a bit strange as the reg gauge does not move at all
     
  18. Chocki

    Chocki Engaging Member

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    It won't, all the air from the regulated plenum chamber is escaping out via the leaking valve seat and on through the barrel port to the outside via the barrel.
    Are you now also saying the bottle leaks as well when removed from the gun?
     
  19. Chocki

    Chocki Engaging Member

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    The end cap / valve guide D36 without the hole right through is for UK sub 12 use to limit the valve opening, but I thought it still needed D38 and D39 to keep the valve centred to the valve seat and act as a valve spring seat, if these are missing and the hole is a larger diameter than the valve stem, then the spring may not be keeping the valve shut properly and it may be out of alignment with the seat resulting in the leak.
    Also the valve spring should be 20mm long not 15mm, if missing the spring seat as well, then it may not be enough to shut the valve.

    Looking at every other comfiguration of FX airguns with similar valves, they all have the spring seat and O ring and the nearest close gun the dreamline definitely has these parts on a sub12 gun.
    Something sounds fishy here, are you sure the owner has not had the valve apart and lost these pieces, they tend to stick slightly to the valve guide when it is removed and can then drop off if not noticed, or if it is a new gun, did the RFD convert an FAC gun to SUB 12 and change the parts omitting these accidentally, i.e. was it ordered from mainland Europe.
     
    Last edited: Jul 3, 2020 at 2:50 PM

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