Pmax 500HK desperation

Discussion in 'Fettling Forum' started by Tonskulus, Oct 28, 2020.

  1. Tonskulus Finland

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    Ok, I've been fettling with my Petromax 829/500HK, chinese model and I'm almost out of ideas.

    It does not burn right or bright enough. There is some flaming outside the mantle but not much. Tested different mantles, Helox, luxor.. same thing.
    Changed many necessary parts: all seals, brand new generator, needle, jet, burner head.. except the J-tube.
    Turning the valve open (pressurezed tank) without top hood, it shoots staright jet of petroleum up to 2 meters or so.
    I also cleaned the J tube, sealed the ends of fine tuning screw which is at vertical position.
    There is no leaks. Used exhaust paste for jet and mixing chamber/burner head.

    One thing I noticed: it burns clearly brighter without the top hood. I also had to adjust the air gap up to 18mm so at first it seems like running rich but why? This lantern would propably be fine using 250HK jet and mantle.

    So the last thing im concerned is the actual J tube. It seems to be fine, but is it really? Well there is tiny dent caused by the tightening screw but could it be causing such a severe burning problems?
    Also I have seen J tubes with and without restriction somewhere beetween 2-3cm from the fuel jet end. What is the actual purpose of this restricted part of J tube? Chinese J tubes has only very sharp edge around there, inside the tube. I removed that small edge and I thing it went even worse..


    tubes.jpg
     
  2. Adrian Romania

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    Inspect closely the J tube and see if it doesn't have a "strangled" area on the inner side of the bend. That could very well explain your problem. Also look very attentive to see if the "hat" assembly that holds the J tube sits correctly (as in stable) on the frame. Some clones have the "hat" cut very poorly where the two spaces for the blocks holding the handle need to fit, resulting in the hat bouncing back and forth and therefore changing the air gap.
     
  3. Tonskulus Finland

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    The hat sits well enough, I actually lifted the whole hat/burner assembly while lamp was lit to add even more distance to the jet. I could lift it about 5mm before mantle was getting dimmer.

    J tube is a bit more restricted at inner side of the bend and overall it did not sit very well in the position. I had to bend it a little to make sure the jet is centered to the middle of J tube intake.

    Poor quality lantern compared to original german made petromax. I have seen some other chinese clones too and they were actually better!

    I'll remove the J tube to take some pictures of it :)
     
  4. Adrian Romania

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    If the J tube is not bent correctly the volume of air is restricted. If the lamp a Sea Anchor? Their quality is the worst I've seen in Chinese clones.
     
  5. Tonskulus Finland

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    This one is "original" petromax, just made in china. Well, maybe I need to get new J tube then. This one also has older style (bigger) ceramic mantle holder and mixing chamber. Those sold today does not fit.
     
  6. Adrian Romania

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    Try to take good photos of the J tube and of the mixing chamber with the ceramic nozzle and post them here.
     
  7. Tonskulus Finland

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    Here you go :)
    I broke the ceramic nozzle while disassembling. It seems like the J tube is out of shape :/


    IMG_20201029_014045.jpg IMG_20201029_013740.jpg IMG_20201029_013617.jpg
     
  8. Adrian Romania

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    Tbh it's not as bad as I expected it to be. The longer straight part is strangled a bit just as it starts from the bend. It also looks like the two straight parts are not parallel (the J is closing a bit, so to speak).

    I'd try with another (good) J tube and see how it goes.
     
  9. Tonskulus Finland

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    I will try, thanks!
     
  10. Adrian Romania

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    You're welcome. :) Let us know the result.
     
  11. JEFF JOHNSON

    JEFF JOHNSON United Kingdom Subscriber

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    Good luck with your fettling!:thumbup:
     
  12. Fireexit1

    Fireexit1 United Kingdom Subscriber

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    This sounds like a probelm I have on a Hipolito. Eventually I worked out that there was a fracture in the J tube - in my case just above the threads for the gas chamber. Try inspecting the inside of the cap for any tell-tale signs of gas burning where it should not ?
     
  13. Graham P

    Graham P Australia Subscriber

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    Are you using petroleum (as in gasolene) or kerosene
     
  14. WimVe

    WimVe Subscriber

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    Send picture to the petromax company in germany and make complain babout quality.
    Then get an old NOS real petromax J-tube.

    I see that after the bend your tube is restricted also the threads are burned away at the burner end, which may indicate that there was a bad fit. Air in/flame out.

    Then with the new part make sure to file of the point of the fastening screw. make sure the clamp holds the tube more then the boltpoint, make no dent.

    I do not understand what you have done with the adjustment screw.
     
  15. Fireexit1

    Fireexit1 United Kingdom Subscriber

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    Good tip @WimVe and answers a question I have had for a while.
     
  16. WimVe

    WimVe Subscriber

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    Well it is somewhat contradictory: there is a screw which interferes with the flow of the mixture so why bother about a dent or shape?
    Well the screw is a way to mix the air/fuel at the start of the tube. The rest of the tube should make a more or less laminar, even flow.
    At least that is my theory.

    Sometimes the mix paddle is gone which changes the noise also dramatically.
    While writing I think about the size of the J-tube. I never measured if there is a difference in size for the different CP between 350 and 500.
    I never bothered because I never downsized a type (500>350).
     
  17. Alex Smith

    Alex Smith United Kingdom Subscriber

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    @Tonskulus I vote a problem with the J Tube. I've had the same experience with a new Chinese Petromax, took me ages to get it to light and run correctly. The problem was only resolved when I purchased a 1970's model and swapped the inner and outer hoods over from the old Px to the new Px. This cured the problem and I was able to then narrow it down to the J Tube being faulty.

    Hope you get yours running correctly.
     
  18. Tonskulus Finland

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    Just got some older petromax parts and there are three different mantle holders/burners. All are bigger threaded ones (old style) and the white one has largest diameter at the tip. The green one has some green paint disaster :D

    Is the white one real original petromax burner? IMG_20201102_123018.jpg
     
  19. Tonskulus Finland

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    I changed J-tube and burner head+mixing chamber to original german made ones. Now it works and is bright enough :)
    IMG_20201102_140815.jpg

    IMG_20201102_203509.jpg

    IMG_20201102_203617.jpg
     
  20. Alex Smith

    Alex Smith United Kingdom Subscriber

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    That's more like it, nice to see! Well done, good effort, you must be pleased with the result.
     
  21. Adrian Romania

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    It was clear since you posted the picture of the original J-tube. :) The original mixing chamber was the one with a rim towards the ceramic burner, right?
     
  22. Tonskulus Finland

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    Yes, the very original mixing chamber is more angular shaped. Well now I need to find another good J-tube. I took that one out from Petromax 523/500..waiting for refurbish.

    So indeed one thing is clear: never underestimate the J-tube being just a hollow tube. I has to be in a good shape! Deformed or otherwise bad J-tube is not going to give good results, it has indeed some important role for overall performance.

    The inner radius of german J tube is also much smaller compared to new "chinese" one. Much better bent to keep the inside diameter constant through the curved part.
     
  23. Fireexit1

    Fireexit1 United Kingdom Subscriber

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    A good effort - persistence normally pays dividends. It looks very good !
     

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