Primus nickel 71, I'm at a loss. Of pressure

Discussion in 'Fettling Forum' started by hikerduane, Dec 9, 2019.

  1. hikerduane

    hikerduane Subscriber

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    Discouraged over this. Put back on my shelf, but today drug it out a few minutes ago. Like I mentioned previously, getting different scenarios/ results, mostly suspicious about lack of pressure, but do get a very slight hiss after running. Also, suspected coked up, plugged, wick too tight, too loose, pushed into tube too far, not far enough, so many things. Stuck the old wick back in but without the original wire, but another wire, tight fit. Took right off but surged some, then surged yellow flames. Shut down and messed with the wick some. Same results, but this time added alcohol to the priming depression while the stove ran and had a great flame for a few minutes, then back to surging of yellow flame until flame was adjusted low, but that caused the flame to go lower on it's own. I had previously cleared coke from the vaporizer and even burned it out, allowing me to blow and suck easily. Maybe not cleared completely? Frustration. Sounds like Mark had mentioned in a above post. I don't have a tiny brush to run all the way thru, just the lower portion.
    Duane
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  2. snwcmpr

    snwcmpr Subscriber

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    What do you mean by that?

    You seem to be losing pressure when hot. I had a crack on a Preston Loop of a Petromax that only showed when hot. I had quenched it. Could not see it.
     
  3. hikerduane

    hikerduane Subscriber

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    I've tried every trick I have learned here over the years and have tried chasing down the reasons for whatever the stove throws at me. When my Optimus 8 or 8R's get going good, after they have run for a while, the tank gets warm and when shut down, when releasing the fuel cap, can usually get a pretty good hiss, some only have a slight hiss, barely heard, harder to hear when rain is hitting the metal roof on the garage.
    I think the next thing to do is remove the wick yet again and see if putting that little brass mesh cap back in, in front of the wick and see if that adds enough thermal feedback to help vaporize the fuel. If that fails, can try what Optimus did on some 8/8R's and wrap the wick in brass mesh. A good soak in hot vinegar might help loosen coke, I usually do that with the mesh from my Primus 96 stoves.
    Duane
     
  4. Marc

    Marc Subscriber

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    What about oil to show leaks, instead of my soapy water idea? Oil wouldn't bubble in the presence of a leak like soap would, but it would give some indication of a leak and not evaporate off until much higher temperatures than soapy water.

    Obviously there are some significant risks to this idea. Mostly just mentioning this so no one calls me out on it, I'm confident you know how to not burn your house down.

    You mention both copper grease and graphite grease on the vaporizer threads. Just to make sure I'm understanding, is that the threads between the tank and the valve assembly, or on the burner bell? It would seem that either of those materials, and graphite in particular, would be an insulator and limit thermal feedback to the burner if on the burner bell threads.
     
  5. hikerduane

    hikerduane Subscriber

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    I'm now thinking more like poor thermal feedback or still some carbon in the vaporizer. I was able to touch the flats on the bottom of the vaporizer shortly after shutting off today. Give it a go tomorrow. Bell is making good contact, plate gets red.
    Duane
     
  6. goldwinger11

    goldwinger11 United States Subscriber

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    Is there a difference between a full tank and a half full tank? I'm thinking that the fuel pickup tube might be cracked or leaking at the top near the threads inside the tank.
     
  7. snwcmpr

    snwcmpr Subscriber

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    I went back through your posts.
    Did you run it before you fettled it?

    When I was a machinist we had a focus group to solve problems that we had. Brainstorming was one method. Listing all ideas and things we had tried. A bad idea often gave rise to a good idea.
    With so many things you have tried. Maybe put all of those in a list, on paper, to keep track.
    I know you are frustrated. I have an Enders that underburns. It now sits on a shelf after many hours of effort.
     
  8. hikerduane

    hikerduane Subscriber

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    I'll look the pickup closer, didn't notice anything the last few times I've worked the wick over, the fuel still has to follow the wick. I had to clear the vaporizer when I got it, only had a really low candle flame the first time I tried to fire it up, tried poking the crud out, that didn't work, that was when I used my torch to burn out the carbon. Maybe this does need that little bit of fine mesh before the wick. It was like a little cap. Some of the Optimus 8/8R's I've worked on had the wick wrapped in mesh, but stoves ran fine without it.
    Working on my gear room/man cave.
    Duane
     
  9. hikerduane

    hikerduane Subscriber

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    @snwcmpr, brought this out again, per one suggestion, wrapped the inserted part of the wick in brass mesh, had to cut one strand off for it to go in. No change, ran a little then spit fuel or burned really yellow. More head scratching, I did not want to exchange vaporizers off a Radius 42 or Military 71, so instead exchanged a jet off one of my Radius 42's. Ran pretty much like it should, so tried to figure out the jet size, I had put a different jet in when the stove ran poorly at the beginning when I first fired it up weeks ago. Figured out what size jet looked like was proper size, stove ran with no surging or spitting yellow flames or fuel so the jet I used originally was too big. I may need to secure the burner plate better, as the bell doesn't seem to get even a light red, but the fount did warm up, so worrying about more thermal feedback may not be needed.
    As I said in previous posts, this stove threw me many different situation/scenarios, so was hard to narrow down what its issue was, so snwcmpr/Ken had a good suggestion to go back and see if something simple was over looked.
    I let the stove run about 10 minutes, no issue, I may go back and replace the wick with more strands.
    Duane
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  10. snwcmpr

    snwcmpr Subscriber

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    The only reason I said that is you are very capable. So something you did or missed needed to be looked at again.
    Yippee.

    Did I read that right, it was a jet change early in the fettle that was changed back?

    Ken
     
  11. hikerduane

    hikerduane Subscriber

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    Ken, yes. I had done a few things, then discovered a few more things as I went, mostly the vaporizer was carboned almost closed, also, would run with a good flame, then suddenly go way down. Hoping I figured this out, only stove I have that wasn't working. Still only a faint whisper when the fuel cap is released, but some of my old 8's do that too.
    Duane
     
  12. snwcmpr

    snwcmpr Subscriber

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    Can you heat the tank with a small torch and get a better flame?
     
  13. hikerduane

    hikerduane Subscriber

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    I had been double priming, will try later, make sure I have this fettled out.
    Duane
     
  14. hikerduane

    hikerduane Subscriber

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    That was short lived. Not maintaining a good flame for 10 minutes, even double primed it, though that helps, burner plate isn't getting as red. I have a new spindle, but it is too slender, so not sure the tip could control vapor. Tightened the jet up, had a candle flame there this second try.
    Duane
     
  15. hikerduane

    hikerduane Subscriber

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    Maybe figured out, fingers crossed. No pressure leak it seems, changed out the cotton cord and put in cotton mop strands which I usually use. Have run the stove twice now without it going out, but seems to like a double preheat. Set it inside the tin it is designed to be used with and let it run over 10 minutes, built up pressure so that the flame was pretty high when the valve was opened more. I think the wick can be tweaked a little, runs just a bit rich and the first run it wanted to spit yellow flame of opened up too much, so think too much fuel is going thru the wick.
    Duane
     
  16. Harder D. Soerensen

    Harder D. Soerensen Denmark Subscriber

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    Good work!
    Do you have a bit of distance (2-3 mm) from the wick to the end of the inside burner tube? Usually there is a small brass wire loop on top of the wick made with the twisted brass wire that runs inside the wick?
    Regarding double prime - my experience is that a good layer of carbon felt will save you the double priming - I’ll be happe to send you a piece of what I usually use?
     
  17. hikerduane

    hikerduane Subscriber

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    I'm out of the brass? wire the wick is knotted to, broke the piece I had today as it had been worked over a few times. Used some other wire I had. Most wicks I have pulled back just a little, this one I added a loose strand on my last try, still just a little loose. That's what I mean by tweaking a little.
    Duane
     
  18. threedots New Zealand

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    Hello @hikerduane .
    At a guess, the jet aperture size might be too large. You may require a jet with a smaller aperture to stop the internal pressure escaping too quick before thermal feedback to the tank can take over(creating more pressure withen than what the jet will let escape during use).
    Hope that helps. John
     
  19. snwcmpr

    snwcmpr Subscriber

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    On a side note.
    Warming the wire when bending can reduce work hardening. Heating after bending can anneal it. That can prevent/reduce breaking.
     
  20. hikerduane

    hikerduane Subscriber

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    John, I had installed a jet the size of my Radius 42's after originally had consulted Basecamp on what # is for the 71, had thought today to see if I can try to see if I have a smaller one.
    Good point to anneal any wire I can find.
    Duane