NRV replacement

Discussion in 'Fettling Forum' started by donv, Jun 10, 2013.

  1. donv

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    Hey all, how tight should i go when putting the new NRV in Optimus 111? This is a brand new NRV and I don't want to overtighten and damage it.
     
  2. SMolson

    SMolson Subscriber

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    Hey Don - First, make sure you use a washer when replacing the NRV back inside the pump cylinder. I tighten them down lightly, meaning not hand-tight as far as she'll go with hand/tool pressure, but a few steps back from that. I use either a lead washer or rubber washer, I personally never replace an NRV without using one. Makes removal so much easier and protects the metal surfaces/provides a better seal. Most new NRVs come with a washer.

    Whether you use one of Stu's NRV removal tools, the generic T-grip ones or the Optimus Hiker spindle (or equivalent), I don't tighten them down too tight (there's still enough play to do another 1/4 turn).

    Once it's screwed in I always test the pressure to make sure it's seated and functioning properly. Replace the pump and fuel cap, turn the fuel valve to off, then generate pressure via the pump. The NRV should let air pass through easily (don't have to pump too hard), that pressure is being generated in the fount (unscrew the fuel cap to hear the pressure release) and that no air is returning into the pump chamber from the fount: visually watch for the pump reversing on its own as pressure mounts in the pump chamber and/or let the stove sit under pressure for an hour then recheck the fuel cap to ensure pressure remains in the fount (audible hiss).

    You should keep the 'old' NRV - why could you not just fix your existing one - was it a formed plug and no brass cup to hold a pip? You can buy brass cups, and of course easily find springs for them and cut your own pip, or buy a new molded pip.
     
  3. NP4-8-4

    NP4-8-4 Subscriber

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    SMolson's reply to donv's question serves another reminder why CCS is such a wonderful forum. It seems that I learn something new about stove maintenance nearly every time I log in. I've replaced a couple of NRVs over the past year or two and had assumed that "finger tight" was enough. SMolsons advice has been printed and will soon be in my growing 3-ring binder of "useful fettling" information. Thanks again all. Perhaps this is the time to open a "Spotted Cow" and retire to the garage for a bit of NRV testing. PWW.
     
  4. donv

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    Got a new one because A&H had them and I figured a spare couldn't hurt. Comes with a lead washer. Thanks for the tips.
     
  5. SMolson

    SMolson Subscriber

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    Hi Don - sorry, I wasn't aware of your Optimus 111 Hiker issues, which as I understand it, is the reason for the NRV purchase. I just read that post so I'm updated now, sorry.

    The fuel in your pump cylinder is most likely due to a dried out pip (plug). I'm guessing, because she's the Hiker model, she has a molded rubber pip with a tapered end that fits into the spring (e.g. no brass cup). Other failures within the NRV is that the spring is no longer sufficiently flexible or has completely dissolved (unlikely in your case due to it being a more recent model of stove). Whatever the case keep that original NRV, they are easy to fix and you (or a stove buddy) can always use spares.

    For reference, this is the inside of a 'typical' NRV (this one an 'older' style, with the brass cup + cork pip). They have not changed much over the years.

    1370837160-IMG_3323_NRV_opt.jpg

    If you're at all interested in opening one, place the head (thicker end, that sticks into the pump chamber) into the NRV removal tool. At the slotted cylinder-tube end that houses the spring/brass cup/pip (e.g. sits outside the pump cylinder and into the fuel tank) place the back (non sharp edge) of an exacto blade (or something similarly thin, long and rigid). Carefully and firmly twist both (or one held firm) hands in opposite directions and the NRV should screw apart. If it does not come apart with hand pressure, let the entire NRV soak in Liquid Wrench overnight, then try again. If again it does not unscrew, there are instructions on this site on other means (leather/slip-joint pliers). DO NOT force it too hard - you can strip, crush and damage the NRV beyond repair (hence the need for spares...). I've replaced close to 50 NRVs now in the last year (including 4 from Hiker model stoves), and have yet to destroy any of them (thanks in large part to Stu's NRV removal tools).
     
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  6. Andy BB

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    Where do we get these removal tools? ie - how to contact Stu? Ah - loco7stove I believe! Found his article...
     
  7. snwcmpr

    snwcmpr SotM Winner Subscriber

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    Best to send him a PT. I, too, will add to the comments of the great quality of his NRV tools, I have both sizes.

    Ken in NC