Optimus 111b - fuel tank bubbling after shut down

Discussion in 'Fettling Forum' started by docnicky, Jan 13, 2022 at 9:21 AM.

  1. docnicky United Kingdom

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    I’m new to classic stoves ad the forum so please forgive me if this is a stupid question.
    I have just stripped down an Optimus 111b and it seems to be operating well with a nice blue flame, good control and no leaks. I replaced the NRV with a new one from Juliands. I used the Fettlebox service kit for the rest and the BD excellent 3 part video.
    When I shut down the stove I can hear bubbling in the tank which stops if I release the fuel cap. It’s more noticeable if the tank has been more pressurised before lighting or running on full throttle.
    Is this normal?
     
  2. itchy

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    I think something similar has been described for hot stoves running on petrol. I assume this is only when the stove and tank are hot. My hearing is not as good as it once was so I may just not notice it.

    As long as it is not leaking anywhere it is likely ok. I am sure you are careful but I'd just let the stove cool off after shutting it down and not risk releasing pressure at the fuel cap. A glowing ember of soot could easily ignite the vapors.
     
  3. docnicky United Kingdom

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    Thanks for your reply itchy, it is just when the burner and tank are hot. I am using Aspen 4 which seems to have a lower boiling point than Coleman fuel from the data sheets I can find. I assume that vapour is bubbling back into the tank from the hot burner supply tube when the valve is closed off.
    I take your point about not releasing the fuel cap until the stove is cool. I have serviced both the NRV and the SRV and I will not pressurise it as much with the pump. It doesn't seem to need it.
     
  4. hikerduane

    hikerduane Subscriber

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    Some of my smaller stoves do that if run for a bit and are pretty warm.
    Duane
     
  5. tretrop

    tretrop Subscriber

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    I would be carefull with the NRV from Juliands, I had some with bad threads in mine that killed an Op 111 and Radius 21.
     
  6. hikerduane

    hikerduane Subscriber

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    I never could get his to thread in, just use them for parts, throwing out the brass "shell".
    Duane
     
  7. tretrop

    tretrop Subscriber

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    Yes, that is what I do now also.
     
  8. snwcmpr

    snwcmpr SotM Winner Subscriber

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    Mine I got were a total QC nightmare.
    I had to finish them. The threads had burrs and were not machined with a lead on the threads. They were oversize too.
    Maybe made to fit the current Asian stoves.
    I have a post somewhere, here, with photos and clear descriptions of the failures.
     
  9. hikerduane

    hikerduane Subscriber

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    I got lucky a few years ago and found some NOS, just use those for really vintage stoves, I try to reuse the old, originals when I can. Got another stubborn NRV in a 45 from the 20's, only weeps a tiny bit so will leave it.
    Duane