An unexpected problem on Optimus 324 Rider

Discussion in 'Fettling Forum' started by john_ger, Jun 19, 2022.

  1. john_ger

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    The symptom:
    The stove started to burn ineffectively, progressively demanding very high pressure inside the fuel chamber just to achieve a low burning.

    Searching the web, i studied pages like this:
    Optimus 324 Rider ridden hard
    trying to understand where the problem might be.
    The problem seems to be inside this tube, shown in the image...

    I was surprised to realize that, blowing with the mouth the one end of the tube, air does not pass to the other side freely.
    I do not understand, what could be the reason of this clog.
    Should not this tube be empty?
    Should not the fuel pass freely inside the tube over the flame to be preheated?

    What might be inside the tube? It seems to be something very hard and of a metallic nature. Any help to understand this puzzle will be much appreciated. Not being a mechanic of any kind, i just gave up!

    img1.jpg
     
    Last edited by a moderator: Jun 20, 2022
  2. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @john_ger The tube has a sintered metal plug inside it at the pre-heater end, presumably to act as a damper for fuel flow.

    Hard to photograph, but you can see it here.

    94F2D2F1-1464-4AAF-BFA1-22718233363D.jpeg


    First question I’d ask is what fuel have you been using? The progressive nature of the problem could be due to the gradual deposition of hard residue from pump gasoline additives.
     
  3. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Also check:
    • that the non-return valve (bottom of pump tube) and the pump washer are working efficiently together - with the stove unlit and the fuel cap removed hold your thumb over the fuel cap opening, pump and feel the pressure developing in the tank (or not!)
    • that the jet is clear and that the jet pricker tip appears when the fuel control spindle is screwed fully clockwise
    • that the jet orifice in the pre-heater is clear …
    … here’s the pre-heater

    EE52B2C3-43AC-4510-A272-4011D359C237.jpeg


    This component. The generator tube pushes into it, making a seal with an internal O-ring. The component screws off the pre-heater.

    F58CD66B-BEA5-489C-AE75-8B2D0BB46ED7.jpeg


    The conical tip of the pre-heater is to the right.

    9410D73E-2CE6-4EBA-80B2-F60D1862F59C.jpeg


    The fuel jet orifice is the one in the centre, at the tip of the cone. The larger hole in the surround below feeds pressurised air into the generator during the pre-heating phase - may as well check that’s clear also.

    55450C39-A1D7-4B24-B785-A85500A0FA1A.jpeg


    Last but not least, and particularly if the fine jet orifice in the pre-heater is obstructed, check that the filter in the base of the pre-heater fuel pick-up tube isn’t clogged. It’s quite possible that that’s the cause of the trouble if it is. Same symptoms occur with contemporary ‘bottle’ stoves like Optimus Nova, Primus Multifuel and the rest if inline fuel filters become clogged, such that replacements are included in kits of spares. Take another look at my original post on the Rider where I adapted another stove’s fuel filter to fit - a Rider spare being unobtainable.

    John
     
  4. john_ger

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    John, thank You very much for your answer, i appreciate!

    A bit crazy but i might say, using this great device for more than 3 decades, i have faced problems included the ones you mentioned. But the technological marvel still works.
    For example - and since experience must be shared :-) - let me show in a picture how i replaced the pump:

    3.jpg 4.jpg

    The pump has severely deteriorated because of hard use. Being a bicycletourist and knowing bicycle tech quite well, i used parts of tube_valves and such and with a pump (this is my spare pump, by the way) the thing works just perfectly.

    OK back to the point - trying to detect the disease.

    I feel forced to the conclusion that the sintered metal plug is clogged.
    ... By what? ...

    A couple of times, i had to clean the "fuel jet orifice", and the "filter in the base of the pre-heater fuel pick-up tube". As for the fuel use historically, i have been using a liquid called here as 'clean gasoline' or 'white gasoline', which is chemically hexane. Compared with car gasoline sold in road stations, it is very clear and leaves no residues. But many times in remote places, i was forced to burn car-gasoline simply because that was what i could find. I always noticed some dirt accumulated inside the tank in the form of rust, and occasionally this dirt clogged the filter or the orifice or the flame regulator. This was not necessarily due to the fuel itself, since i have been in really wild humid places, i must say.

    Now it seems that the dirt has accumulated in that metal plug. I already tried a chemical cleaner, but no success. I really have no idea what to do.
     
  5. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    You say not, but you’re to be complimented on what you’ve achieved in checking things out. I like the bike pump adaptation. Amish folk use a fuel cap incororating a shraeder valve to pressurise Coleman stove and lantern tanks with a separate pump, so you’re in good company.

    70381EC2-CBF7-4218-A9D7-12549D6A32CB.jpeg


    It’s possible the occasional draught of pump gasoline has messed up your Rider’s generator but I wouldn’t despair. Firstly, I’d try heating the generator up to a dull red heat (off the stove!) with a blowtorch. My reasoning is that any additive residue ‘stuck’ to the sintered metal plug could well have the bond loosened at that sort of temperature. Then, tap that end (gently so’s not to distort the metal) on a hard surface to dislodge the residue. Ideally, with an airline blow through the generator from the valve end (temporarily install the jet nipple to block off that outlet).

    If that doesn’t work I’d drill through the plug with a 1.5 mm drill. I doubt it would upset fuelling and the alternative would be a non-functioning generator.
     
  6. john_ger

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    John, you come as my saviour for the second time. The first time i had a leakage in the regulator - i could not find graphite sheet but i found a relevant heat-resisting material named permanite, which did the job.

    I burned the tube on flame till it got dark red. Worrying to not deform the tube in anyway, i waited a few minutes till it got cold, and tapped it softly on white surface, to my joy seeing a bit of dirt falling out! That was it! I repeated the process 4 times till no dirt came out.

    Strangely now the priming of the Rider changed a bit, but after one minute or two the thing burns absolutely charmingly.

    5.jpg

    Thanks to You, and thanks to the guys who made this page! ;)
     
  7. john_ger

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    Oh, and thanks for the idea for the pump to be attached directly on the tank lid. ;)
     
  8. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    I’m glad that resolved the problem. Combustion’s looking good.
     
  9. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Well it works for Coleman because of their failsafe measures to prevent fuel leaks - NRV (check valve) that can be positively locked shut; NRV not immersed in fuel but inside a jacket around the pump tube.

    On the Optimus you’d be dispensing with the Safety Release Valve in the fuel cap and that’s worth retaining.
     
  10. Majicwrench

    Majicwrench Subscriber

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    My 324 sprung a leak a year or so ago, you are inspiring me to get it out and get it fixed.
     
  11. john_ger

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    I believe this problem was the last for me on this technological marvel.
    I want to know that i can fix any possible problem on the field.
    For me reliability is the most important in the middle of nowhere.
     
  12. john_ger

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    Additional information:
    to prevent any distortion of the tube's end (where it inserts into the preheater's O-ring), i hit the tube strongly with a metal object (screwdriver) and more dirt came out...!
    Now i can say the tube is ready to fly for 3 more decades... ;)
     
  13. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Huge respect to you for seeking (and achieving) that with an Optimus 324 of all things! It wouldn’t be the first choice of most stove enthusiasts to rely on in remote locations. That said, it’s well made and easily dismantled. The two O-rings in the pre-heater are potentially a source of a fuel leak and with the unavailability of a service kit of spares, fuel-resistant equivalents would have to be found.
     
  14. john_ger

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    I wonder if i can have spare ones for these O-rings. Are not ordinary ones?
    I am not sure, because i am thinking that at this spot the temprerature is not very high.
     
  15. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Getting the right size would be the first step. Durability and fuel resistance the second and third. The pre-heater rotates through a small arc on them, hence my comment on ‘durability’.
     
  16. john_ger

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    For the history, in my town i found the two O-rings, at about the same dimensions.
    Strangely enough, now the Optimus burns like hell, just like a brand new one!
    :D/