Optimus 8r Flare Up

Discussion in 'Fettling Forum' started by E.B., Dec 4, 2021.

  1. E.B.

    E.B. United States Subscriber

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    I recently purchased a 1980s Optimus 8r for a reasonable price. Cap gasket was good so I fueled, primed, and lit it. A new stove does not officially have a home with me until it has brewed some coffee, so I let it warm up and set on the pot. Once it got hot, with a nice blue flame, I would get random shots of liquid fuel through the nipple which of course flared up.
    I am more familiar with the vaporization process of my 96, 00, and Coleman stoves so this is a mystery to me. I have looked at the parts diagram and wonder if the wick is not doing its job?
    Any suggestions?
     
  2. hikerduane

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    Try it a second time, I wonder if the wick gets a slug of air and needs to work itself out. I've had a couple do like you describe, even one for a little bit when I had done nothing and it had run perfect 6 months or more before.
    Duane
     
  3. E.B.

    E.B. United States Subscriber

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    I took your advice. I filled the tank to minimize the possibility of air and lit it off. As you well know, 30 year old stoves that have received minimal maintenance soon let you know. The flame was weak and soap solution showed a leak at the relief valve. I imagine the pip is toast, so I have to borrow my friends penta wrench and see about that.
    Come to think of it, maybe a full tear down and cleaning is in order…
     
  4. hikerduane

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    Leave some space for air so it will gain pressure.
    Duane
     
  5. Majicwrench

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    I've had stoves do that ----spit a bit of fuel?, orange yellow, rich-- and pondered if there wasn't a bit of something else in the tank or in wick. But just guessing. None have seemed to do it after running a good while.

    Let us know how it goes w new pip.
     
  6. snwcmpr

    snwcmpr SotM Winner Subscriber

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    I would add that you could have given time for the wick to get saturated before lighting it.
    Any wick stove let to dry put will need that saturation time.
     
  7. E.B.

    E.B. United States Subscriber

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    My description was quite abbreviated. When I fueled it, I left it over night for the wick to become saturated. When lit, it burned with increasing strength as it warmed up. I heated water and enjoyed a cup of coffee. When I lit it, and got t running at full strength, a second (and subsequent times since) it displays the random shots of raw fuel and flare ups. This is a minor annoyance that the fettler in me wants to correct.
     
  8. BradB

    BradB United States Subscriber

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    Yes, replace the pip in the cap. While you are at it, why not replace the cap gasket so you don’t have to think about that for 10 more years. And I never fill more than 2/3 full.
     
  9. snwcmpr

    snwcmpr SotM Winner Subscriber

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    Ok, understood.
    If, after replacing the gasket and pip, it still does it, I would look at the wick.
     
  10. Majicwrench

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    @snwcmpr is that in the 8r instructions?? Always wondered......it doesn't take long at all for CF to flow an inch on a cotton wick.
     
  11. hikerduane

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    I've had the flaring with a wet wick, but I've also had the vaporizer out of the fount sorting out the issue. At times seems selfhealing. Position of wick? Mystery.
    Duane
     
  12. E.B.

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    Well, everything appears to be ok now. I tore it down and the wick was quite discolored at the burner end. I didn’t have any mop strands (or was too impatient) so I cleaned it with carb cleaner and put things back together. I used the filler cap off my 123 and fired it up. One pot of coffee later and it is running like a champ and even seems to be more robust than before.
    Thanks Duane and everyone else for getting me on the right track.
    Now on to the cap overhaul.
     
  13. Majicwrench

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    Excellent. It will certainly seem more robust now if the other cap was leaking, being airtight is huge on these
     
  14. ArchMc

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    I had something like this happen with a Svea 123 that someone gave me to repair. Would burn fine for several seconds, then either flare or blow itself out. (It could be relit if I was quick.)

    I asked the guy what he had done to the stove, and he said after using it camping, he had rinsed the tank out with rubbing alcohol.

    My “repair” consisted of running the stove (with a lighter handy) until it repaired itself and began burning normally.

    ….Arch
     
  15. hikerduane

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    I've had no trouble with my 8/8R's, just a couple like the Primus 71 and once with my Primus military 7 which initially ran great. The one 71 gave me fits, worked itself out some how, wick thickness and insertion depth are supposed to affect things.
    Duane
     
  16. snwcmpr

    snwcmpr SotM Winner Subscriber

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    Just said what I would do. I don't read instructions. I am a guy.
     
  17. E.B.

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    After watching a Bernie Dawg tutorial on 8r repair I can’t help but wonder if part of my flare up problem might have been a wick inserted too far into the valve body.
    The tutorial showed the wick being inserted all the way and then withdrawn slightly to provide a gap for vaporization. Seems to make sense.
     
  18. BradB

    BradB United States Subscriber

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    Slightly withdrawing the fully inserted wick has made my Svea 123, Optimus 8R, and Optimus 99 all burn a bit stronger.
     
  19. Majicwrench

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    I shove wicks in all the way