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Kral Np-02 'power Wheel'

Discussion in 'Technical' started by stevew71, Sep 16, 2021.

  1. stevew71

    stevew71 Well-Known Member

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    I've had this NP-02 for a few months, purchased second hand. When I picked it up there was a slight puffing at the power adjuster on the marked/gauge side, as the gun had been stood a while I guessed that the o-rings had hardened/failed. I'd read that this was a weak area on these rifles but wasn't too bothered. On inspection there didn't seem to be any damage to the o-rings but they were replaced anyway and a smear of silicon grease applied and all was good - no more puffing on test.
    Or so I thought
    Took the rifle to the range to set up and after a dozen or so shots the puff returned.
    I've changed the o-rings a couple of times since - no visible damage and all good for a few shots then the puff returns like a dodgy curry from the night before. I'm not 'using' the power adjuster, it's just set to full as that's where it will be used and zeroed so there's no movement/rotation against the o-rings.
    I had another go yesterday and for good measure removed the barrel to check for burrs on the TP. There wasn't but I gave it a tickle with a bearing dipped in lapping paste just in case, even though the power adjuster doesn't make contact with the barrel. There were no discernable burrs in the block the adjuster fits too (slid a cotton bud in and didn't feel any snag).
    And the same thing occurred, good for a dozen shots then puffing again.
    The o-rings I am using are 3mm ID / 1.5mm thickness (for a OD of 6mm) - I got this size from another forum, can anyone confirm these are the correct size ?
    If they are correct does anyone have any suggestions on curing this ?- when it's not puffing it's superbly accurate, especially with Mako slugs, but once it starts to puff the consistency goes out of the window, getting worse with heavier or tighter pellets - to be expected given the extra resistance before the pellet gets moving.

    Cheers

    Steve
     
  2. Bladesmith

    Bladesmith Big Poster

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    Does there feel like the button pushes in to easy you should feel some resistance on the rubber
     
  3. stevew71

    stevew71 Well-Known Member

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    There was always a little resistance on fitting/removal, an even drag. This last time there was a definite 'stop' (using better grade o-rings) as on refitting for the last few mm that required a firmer push that 'popped' the adjuster home
     
  4. dodgyeye

    dodgyeye Donator

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    I've noticed that occasionally and put it down to it being restricted to 12ftlb, TP, adjuster wheel and anti tamper brass bung bleeding off power to meet UK restrictions. I see no power loss within 12 ftlb from it doing it. It might only be when it's filled up to the limit, as can't say I've noticed it at lower power air pressure levels.

    I read that the wheel adjuster only really for full power over 12 ftlb countries, as it doesn't do much at all at UK power levels. I think that's from the Kral manual I'll try and dig it out.

    I haven't had mine apart so AT brass bung still in place, had mine brand new so lifetime warranty from shop, so can't comment on internals.
     
  5. Wayforward

    Wayforward Engaging Member

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    Is the full power setting actually full power on yours? When I was fettling mine I noticed that the port was fully open 1 position back.
     
  6. stevew71

    stevew71 Well-Known Member

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    yes. based on threads I've read I was quite surprised that all the ports line up
     
  7. Wayforward

    Wayforward Engaging Member

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    I guess a chrono test will tell for sure.
     
  8. ZAKDINGEL

    ZAKDINGEL Busy Member

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    The power adjuster dose nothing on a 12flb model it only is adjustable on the Fac models I was told this by range right when I bought one mine was back a forth with leaks and accuracy issues more than stripe on a tiger :rolleyes:
     
  9. willo1962

    willo1962 Big Poster

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    Yes it does. My friend brought his around to mine and it went from 11flb to about 3 if I remember, could have been a little less. It was a new model with the improvements
     
  10. ZAKDINGEL

    ZAKDINGEL Busy Member

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    Maybes they do now but I had one of the first ones and it done nothing then again I had nothing but trouble with it so maybes it was knackered ?? it would even move that's why I asked range right they reply was that's because its not a fac model as they were a brand new gun to the uk market I had to take they word on this --it was sold after the fourth time back from them the leaks
     
  11. Peddy

    Peddy Busy Member

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    I had same problem with a puff of air from the adjustment wheel. Replaced the seals with a coating of silicon grease all over the adjuster, not had a problem since. Maybe try a harder seal day shore 90. Size wise I can’t check if I have any spares for a week.
     
  12. Peddy

    Peddy Busy Member

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    1.6x3.1mm from a quick search
     
  13. stevew71

    stevew71 Well-Known Member

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    Cheers @Peddy - I'll delve into the "box o' spares" and see what I have amongst the o-rings. I was considering going up a notch on the thickness to see if it helped
     

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