Optimus 96 Flame Issues

Discussion in 'Fettling Forum' started by Cookie, Nov 29, 2019.

  1. Cookie

    Cookie United States Subscriber

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    I recently got this newly acquired stove running and replaced the fill cap and tank seals, nrv, and pump leather. The stove fires right up after the usual pre-heat but never gets a blue flame and it appears as though I have something going on insofar as one section of the flame is larger than the rest or more appears to have more yellow in the flame at times. I suspect that the slightly enlarged intake holes in the burner bell from a previous removal attempt and the slight warpage of the bell (midsection of the bell) may be the culprit there but am unsure. I have tried shimming the bell higher and it gets worse. I have also tried rotating the flame spreader in an attempt to make the location of the excessive flame move (checking flame spreader) and that did not help. When rotating the burner bell the flame in question seems to follow the bell. I can't seem to locate another burner bell to try on the stove to rule it out.

    I tried to check the lipstick burner with a prickler for excessive wear only to discover that all of my prickers were undersized when measured. The lipstick burner has some old metal screen in it and I'm eventually going to replace it with some new screen.

    The following pictures represent 2-7 pumps after warming it up. The flame pattern does settle down with a pot on it to an almost acceptable level but there is a evident area of about 25% of the flame that is leaving heavy soot all over the pot. Lastly, the stove does not "roar".

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    Last edited by a moderator: Nov 29, 2019
  2. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi, the brass mesh is important as it helps with fuel heating/vaporisation. Have a look at this post:

    Vaporisation Gauze for No.96 and No.100 stoves.

    You have given the stove very few pumps but you have a big, lazy, fuel rich flame. It is likely that the jet is bigger than the 0.23mm (9 thou) diameter specified. You should also ensure that the tank is never more than 3/4 filled.

    An easy test to see if you are suffering from too much fuel exiting the jet is to get the stove running, then grip the flame-plate in a pair of snipe-nose pliers and carefully lift it upwards by a few mm. If the flame becomes blue (because of better air mixing) you have confirmed an over-rich mixture.

    Hope this helps.
    Best Regards,
    Kerophile.
     
    Last edited: Nov 29, 2019
  3. itchy

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    @Cookie

    The screen inside the burner is easy to clean. Pull it out, and if it looks dirty, unroll it. Some use a solvent to clean it up but I just heat it with a propane torch to burn off the crud. You might be able to clean a little carbon out of the burner tube as well. Hopefully that will help a little.

    The bell looks ok to me. I'd guess that if your prickers are all smaller than the jet, the jet is likely worn and a bit on the large size for this stove.
     
  4. Cookie

    Cookie United States Subscriber

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    @kerophile and @itchy Thanks for the info. I had pre-cleaned the brass screen in my initial fettle and ensured that it was in salvageable condition for initial firing. I also wanted to make sure than it wasn't smaller than normal in case someone before me had trimmed it just in case. I raised the bell off of the lipstick burner while running and it got better when raised very high above the burner. When I initially tried this I apparently didn't raise it high enough to see the change. For some reason I was thinking that the jet needed to be .32 and that my .23 prickler was just undersized. I now remember which was which and agree that the burner hole is too large...On to more fettling

    @kerophile I saw your old post on the mesh. The fettlebox didn't have any listed. What mesh size should I buy for the 96 ? Thanks
     
    Last edited: Nov 29, 2019
  5. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  6. Lennart F Sweden

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    I don't know the mesh size but it is a quite fine brass mesh.
     
  7. hikerduane

    hikerduane Subscriber

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    Mesh can be cleaned in hot vinegar for half an hour, then brushed with a brass brush. Sounds like you need to peen the lipstick. I've found even younger stoves need that.
    Duane
     
  8. hikerduane

    hikerduane Subscriber

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    I should add, a couple flame plates were off, messing with the flame direction. Using another flame plate corrected that issue. I have numerous Primus 96's and a couple Optimus 96's.
    Duane
     
  9. Cookie

    Cookie United States Subscriber

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    @hikerduane Thanks for the tip

    I cleaned the screen and was amazed at what came off it. I peened the lipstick burner twice going gently using a 1/4" socket extension and a small brass hammer that I use on firearms. I added a aluminium shim made from a soda can to raise the burner height. Also, as a note I had to apply a small amount of copper anti-seize to the burner and bell because they will not come apart after one firing without the use of my break caliper bell removal tool. It still has a little yellow at the odd flame side but disappears mostly when a pot is placed on the stove. There is now zero soot on the pot and the flame marks look rather even on the base of the kettle. Lastly, I noticed that the bell glows at full throttle after about thirty seconds but is only noticeable in the dark. Is that normal ? Thanks



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    Last edited: Nov 30, 2019
  10. hikerduane

    hikerduane Subscriber

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    I can't get all my 96's to run perfect, wish I could see a very magnified image of the orifice. Some run red hot, some run good but dont make the parts red hot or slow to get there. Just the way they are, I dont believe all run as we are lead to believe. Can't always get the peen job perfect, but it is much better.
    Duane
     
  11. Tony Press

    Tony Press Australia Subscriber

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    @Cookie

    That looks good. :thumbup:

    No soot is the best test.


    Cheers

    Tony
     
  12. Cookie

    Cookie United States Subscriber

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    @Tony Press Thanks Tony and thanks to everyone who offered advice on this en-devour :content:
     
  13. snwcmpr

    snwcmpr Subscriber

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    Is there a reason that the lipstick was only used for a few stoves? Not a successful design?
     
  14. Ed Winskill

    Ed Winskill United States Subscriber

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    Well, when Manaslu brought back the 96, it had a 'standard' burner.

    How many threads and tutorials have we had over the years here about fixing the jet aperture on the lipstick burners? Many....a bit more complex than screwing in a new jet!
     
  15. hikerduane

    hikerduane Subscriber

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    I was disappointed when I got a Manaslu 96, failed to notice it wasn't a lipstick as I wanted another brand of lipstick to go with my others.
    Duane
     
  16. Ed Winskill

    Ed Winskill United States Subscriber

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    Puts me in mind of the 2005 Telegraph obituary of Air Commodore Sir Archie Winskill, a Spitfire ace in WWII and later Captain of the Queen's Flight. I had the honor and pleasure of spending several hours with him in 2002; something I've told about here before.
    He was a close friend of Queen Elizabeth the Queen Mother. The obit closed with the following words, as I recall them: "Archie Winskill was a man of great charm and courtesy. The Queen Mother was once heard to say of him, 'It's for men like Sir Archie that makes it worthwhile to put my lipstick on in the morning.' "

    Something charming about the lipstick burner; practicality isn't everything.
     
  17. Simes

    Simes Subscriber

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    I'm on the way....
    Perhaps the configuration enabled it to be a far more compact kit when boxed, possibly.

    I've found a stove leg through the bell slots when still warm and give a quick twist loosens the bell before it gets a chance to get too tight.
     
  18. Javerjayal

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    mixture of kerosene and gasoline helped me with the problem like yours.
    the gas outlet is enlarged to .030 mm
     
  19. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @snwcmpr You asked:

    “Is there a reason that the lipstick was only used for a few stoves? Not a successful design?”

    Lipstick burners are a simple form of vaporising burner and they are easy to de-coke if your are dealing with low quality kerosene, as was the case with early stoves.

    However the design is power-limited by the vaporising surface area you have for a given lipstick size. If you want a compact, powerful burner you need to go to a multi-tube vaporising burner such as the 4-tube design which became the industry standard quite early.....1880s?

    It is a similar logic to the move from simple kettle type boilers to multi-tube boilers for steam production.

    Best Regards,
    Kerophile.
     
  20. Twoberth

    Twoberth Spain Subscriber

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    Great explanation George. Simple and easy to understand.