Soto Muka gasoline stove

Discussion in 'Japan' started by presscall, Oct 10, 2014.

  1. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Doc Mark's video tests of this model caught my attention and inspired me to try one out myself but not being too eager to fork out the full market price for a new one I held out for a good used example.

    Eventually one came my way, barely used, with stuff sack, instructions and box and with an unmarked, undented 700cc fuel bottle, sold separately when the stove is bought new


    1412974169-1.JPG


    The instructions warn that the burner vapouriser's performance worsens over forty or so fuel bottle-fulls of burning time, so I stripped the generator to see what might degrade.

    Here are the component parts. That up-tilt of the jet-end of the vapouriser is an intentional offset to induce fuel/air mixture swirl in the combustion chamber and isn't due to my heavy-handedness during dismantling

    1412974178-2.JPG


    Here's where the jet nipple goes, a fine brass gauze strainer in place. This view shows the air inlet openings too, enabling the air to scoot in past the jet, which seems an efficient way to go about things

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    There's a tiny component, an Archimedes Screw sort of thing, that fits inside the jet. At first sight I fancifully imagined it rotating at high speed, turbo-fashion, then realised it stays put and creates a whirlpool effect on the vapourised fuel stream, contributing to better mixing with the air and more consistent combustion - presumably.

    I thought of that dodge to empty water out of an up-ended bottle quicker than just letting it glug out, by giving the bottle a quick flick-twist to rotate the water in the bottle to create a whirlpool in the neck, speeding up the exit of the water considerably

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    The vapouriser/generator has a coiled steel wire core

    1412974215-6.JPG


    Other end of the vapouriser is this component, which is a swivel joint ...

    1412974223-7.JPG


    ... fitting in this banjo connector on the flexi-hose

    1412974233-8.JPG


    On the other end of the flexi-hose is this connector ...

    1412974250-9.JPG


    ... which pokes into that connector on the fuel pump ...

    1412974264-10.JPG


    ... a quick-lock fitting arrangement. Very smooth action, very secure and - as long as the O-rings in there hold out - fuel tight

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    Ah, the pump. More complex, by quite a degree, than a simple Ergo pump from Primus. But then, by means of a clever rotary valve arrangement (demonstrated on the Soto website HERE ) the pump creates a suitable fuel/air mixture for starting up the stove with minimum flare and offers an air purging setting to clear fuel out of the fuel line when the burner's been shut down. Additionally, the control knob pulls out on a click-stop to operate it and this provides a safety feature whereby pushing in the knob to its stowed setting, whatever the flame setting, shuts off the fuel

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    The pump non-return valve and gauze filter in the pump housing for the valve

    1412974306-14.JPG

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    I'm not too fond of pump cup washers that aren't oiled leather ones to be honest, but this is a big improvement on those Optimus 111T O-ring versions

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    The control knob

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    An indicator, here with the fuel bottle depressurised ...

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    Emerges when the bottle's pressurised and reaches optimum pressure when the red line's reached

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    Wide-mouthed fuel bottle

    1412974390-19.JPG


    MORE TO FOLLOW - AND FLAME SHOTS
     
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  2. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    With the vapouriser removed from the stove, these are the only remaining components

    1412977151-21.JPG


    Fuel/air inlet

    1412977161-22.JPG


    ... and outlet in the combustion chamber beneath the burner rose

    1412977170-23.JPG


    It's an alloy casting, which gets warm in use but is sufficiently out of the burner blast so that there's no molten pool of ally during a firing, thankfully

    1412977181-24.JPG


    The burner rose and mounting arrangement

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    With the jet and air inlet housing inserted into the inlet tract of the stove body, the vapouriser is clamped in place with just one set screw

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    The instructions with the stove explain that though securely held in place, the clamping arrangement allows for a degree of movement to cater for thermal expansion of the vapouriser in relation to the stove housing

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    A quick and easy start-up with no priming and maximum output is a scorcher, followed by a medium setting and what passes for a simmer

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    I said, "... what passes for a simmer". Well, there is undoubtedly a wide range of output settings to be had with this stove but you've to bear in mind that the range is from excessively hot (do I need a litre of water to boil in half-a-minute? Don't think so) to a 'simmer' that's more like a moderate setting on another stove.

    In fact it's possible to tease out a simmer lower than the example I've pictured, but it's a bit of a fiddle to get it to stay stable.

    That might be a big no-no for some people, but the way I'll be using the Muka is as a water boiler on hikes and tended-to with regular stirring, heating up soup on the lowest setting.


    Cooled and stowed. The flexi-hose, helped by that pivot joint of hose to burner, is amazingly flexible. No spring in it at all. I'm reminded of those techie garden hoses that roll up to nothing compared with conventional hoses. Very effective

    1412977317-36.JPG

    1412977334-37.JPG

    John
     
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  3. theyellowdog

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    Fantastic post Presscall.
     
  4. snwcmpr

    snwcmpr Subscriber

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    Thank you John.
    Nice photos, as always, and a nice description.
    I got one when REI quit selling them, and it was priced way down.
    I think I will keep it in the box, unfired, for now.

    Ken in NC
     
  5. Doc Mark

    Doc Mark Subscriber

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    Hi, John,

    Excellent post and photos, as usual, and much appreciated! Like you, I found the Muka to be an excellent performer, and well designed in lots of ways. However, I was able to coax a simmer out of it, but as you say, it does require quite a bit of fiddling to make it happen. I've not had much time for stove testing, for quite a while, so I've not seen how that simmer will last in actual cooking situations. I am pretty sure your comments will ring very true, when I finally get to cook something on my own Muka. To me, this stove is WELL worth owning and using, and it's very light weight, and amazing power, should make it a favorite with the "gram weinies" out there. Don't know how easy it will be to get one, as it also seems to be in the "close-out" bins at REI, and other places. Thanks, again, for another of your top of the line reports, John!! Take care, and God Bless!

    Every Good Wish,
    Mark
     
  6. jbf

    jbf Subscriber

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    John
    great post and pictures. :thumbup:
    thank you,
    John
     
  7. kerry460

    kerry460 Australia Subscriber

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    G,,day John .
    I have never been a fan of this style of stove .
    for no obvious reason .

    this appears to have a lot of very well thought out features incorporated into it .

    very well detailed write up and photos .
    thanks .

    cheers,
    kerry
     
  8. mr optimus

    mr optimus Subscriber

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    Hi John outstanding, pictured tutorial of the Soto Muka stove.

    I have seen and Doc's video on youtube, which I was very impressed with through out, the performance quality and performance.

    The Soto Muka is a superbly engineered stove, with its many components. This is a fantastic post for all of us who acquire one and need to strip it down to service.
    Well done John as all ways
     
  9. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Hi All, good to hear from you.

    I'll be using the Soto over the weekend, undoubtedly with the foil windshield and ground disc if the wind keeps up. I'll persevere with the simmering capability, with burnt food the penalty for failure!

    Back to that vaporiser/generator life issue flagged up in the instructions that I mentioned but didn't give my thoughts on. The manufacturer encourages the use of unleaded pump petrol (gasoline) as well as Coleman fuel or equivalents.

    It seems to me that in spite of the assurance that the stove is designed to take pump petrol, the generator's bound to suffer a reduced life due to the deposition of residue of fuel additives. I suspect that Soto have put that warning in with that in mind. I'll be using Aspen 4T exclusively and expect to get an extended life out of the generator, as has proved the case with my other gasoline stoves.

    Generator aside, I believe it's the profusion of O-rings in the design that will kill off the stove if genuine Soto spares sources dry up and equivalents can't be found, given that the stove relies on precision machining and approximations aren't likely to be good enough.

    Certainly I'll not be dismantling the rotary valve in the fuel pump in a hurry but reckon there are at least six O-rings in that, plus spring-loaded plungers that look difficult to reassemble. Then another three on the hose swivel-joint, probably three more on the quick-release hose connector on the pump, two in the non-return valve and the pump to bottle seal of course.

    John
     
  10. kerry460

    kerry460 Australia Subscriber

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    John , a suggestion .
    if a parts kit containing all the o rings is currently available at a sensible price .
    i would buy one , and get the sizes and hardness of the o rings checked out for availability .
    much easier with new ones than to try and figure it out from old worn ones .

    just a thought .
    cheers,
    kerry
     
  11. snwcmpr

    snwcmpr Subscriber

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    John, have you tried to simmer with less, as in a minimum, pressure in the tank? That works with the MSR remote tank stoves.

    Ken in NC
     
  12. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Hi Kerry, Ken.

    Very good thinking, Kerry, and I'm with you on that, having ordered a spare generator, which comes with the pivot bolt and O-rings. The only other spares kit is to service the non-return valve in the pump and includes an O-ring for pump-to-bottle.

    There's the problem, apart from the NRV the pump's not user-serviceable, so the outlet connector O-rings and the rotary (Soto call it a 'drum') valve in the pump is forbidden territory. That wouldn't put me off delving in there if it stopped working, but it's an unknown quantity on the O-ring sizes until I do.

    Ken, turns out I was wrong, the stove simmers. Doc was perfectly right and it's not fiddly at all. Although as you point out reducing bottle pressure on other bottle stoves helps, on the Soto it doesn't. It messes up the fuelling big-time and leans out the mixture to become unburnable - poof! and the flame's gone.

    I put it through it's paces today, not on a hike, but on the patio at least.

    First off, I was too quick switching from 'Start' to 'Run' and un-vapourised fuel pooled in the burner combustion chamber.

    Sooted-up outside ...

    1413035055-38.JPG


    ... fuel-wet inside

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    And here's the simmer, with the setting. Beauty of that dial with its obvious markings is that the setting's repeatable, once remembered

    1413035077-40.JPG

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    The 'Start' procedure depletes bottle pressure quite rapidly, the rotary valve taking air from that upper inlet pipe (above the fuel when the bottle's horizontal) and neat fuel from the lower pipe, then mixing the two as a Coleman quick-light has been doing for decades. Like a Coleman, it's necessary to keep pumping during the start-up phase to keep the pressure up

    1413035360-42.JPG


    It helps that provided the fuel bottle's not overfilled, setting it vertically for easier pumping action still keeps the air inlet pipe above the fuel ...

    1413035379-43.JPG


    ... then laying the bottle horizontally again when the fuel pressure's restored and 'Run' is selected

    1413035446-48.JPG


    A moderate setting here, enought to get my 1 pint capacity kettle boiling pretty quickly

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    Heading for a simmer now ...

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    Simmer

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    Real test was cooking lardons and onions to go in a cornbread bake. Perfect control, I'm glad to say

    1413035481-50.JPG

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    Simmering at the bottle pressure the manufacturer intended

    1413035518-51a.JPG


    Cornbread mixture (actually, 'wheatbread' made with cous cous since I'd no cornmeal in the store cupboard) ready to go into the oven

    1413035535-52.JPG


    Although I daresay I could have got the Soto to power up my Coleman oven - oven on bricks, Soto at maximum heat to achieve the required 400 degrees Fahrenheit oven temperature - I opted for my Taylors paraffin stove

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    Soon got up to heat

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    Once arrived at, the fuel pressure could be dropped to maintain a steady temperature, other wise it'd send the oven dial off the gauge

    1413035652-56.JPG

    CONTINUES
     
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  13. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    While the bread was cooking, I used the Soto to boil up a kettle of water to wash the preparation dishes - a four-pinter stainless steel Thekla (Germany) kettle this time

    1413037260-57.JPG

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    Fuel pressure still as recommended and good to note that it didn't drop during the time the kettle took to boil

    1413037287-59.JPG


    Bread's done

    1413037306-60.JPG


    Glasses of red wine, spot of mixed salad to accompany

    1413037318-61.JPG


    John
     
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  14. Doc Mark

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    Morning, John,

    Excellent addendum to what you originally posted, and I loved seeing the Muka cooking up your lardons and onions!! With such clear and sharp photos, it's easy to see just how good the simmer can be on the Muka, and you really did the stove, and yourself, proud, John, by the quality of your photographs in this report!!! Well done!! Another thing about this Muka that I love is the soft flexibility of the fuel hose, as you have mentioned. Hard to believe just how small and light the burner is, when all folded up, and the fuel hose coiled around it!! Slip it into it's bag, and then into your jacket pocket, then put the smallest fuel bottle offered, and pump, into your day pack, and you're off on a nice day hike adventure!!

    I also agree with you about the dearth of spare parts available for ready purchase, and second the recommendation to get spare parts kits whenever they are found. Thinking back to the little Sigg Fire-Jet stove, for which you very kindly cobbled up a better fuel line/connector setup for me, I remember that Sigg did not offer spare parts, back when the Fire-Jet was first offered. That was a real problem for many owners back then. Later, when a small parts kit WAS finally offered, the stove had already fallen from popularity, and those kits became very hard to find. Luckily, Trojandog found some in Germany, and now my Fire-Jet stoves can have a nice, long life, should I need spares in the future!! So, as you have so rightly mentioned, getting spare o-rings, and other spare parts, is of paramount importance, when thinking of helping our Muka stoves to have a nice, long service life!

    Finally, I absolutely agree that the dire warnings published in the Muka paperwork, about the generators not having a long service live, are pointed squarely at those who choose to burn unleaded auto gas in their Muka stoves!!! I will NEVER do such a thing, as I already know that, at least in the US, unleaded gas will clog up most any stove in which it is used, especially if used on a regular basis! So, like you, I'm sticking to Coleman Fuel in my Muka, and thus far, I've not had even a tiny hiccup from doing that.

    Thanks, again, John, for this most excellent report, and very, very well done, my friend!! :thumbup: :clap: :clap: :D Take care, and God Bless!

    Every Good Wish,
    Mark
     
  15. Metropolitantrout

    Metropolitantrout SotM Winner Subscriber

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    There are several reports of this stove with photos of the body (which appears to be cast) cracking and breaking when used in cold weather.

    You can dig up the customer reviews on REI.com and scroll down to the bottom for one review with photo.

    http://www.rei.com/product/815135/soto-muka-liquid-fuel-stove#reviewsTab

    Even though its no longer for sale you can still read the reviews. Said review is almost at the bottom of page.
     
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  16. Doc Mark

    Doc Mark Subscriber

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    Hey, Metropolitantrout,

    Interesting comments, but I, for one, put very little stock in many reviews of that nature. Having seen far too many people try to use stoves in the wilderness, who don't know their elbow from their baby toe, it's pretty easy to see how they do things wrong, and in so doing, almost always blame the stove (lantern, gun, pump, bike, or "fill in the blank"!)

    Both Presscall, and myself, have proved that this stove can, indeed, simmer. But, look at all the reviews that emphatically state that it cannot!! For those who say that Soto needs to "completely redesign the Muka, and it's pump", I say, "Let's see the stove and pump that YOU can design, Dude"!!!! The Muka is an outstanding design, and BY DESIGN, it requires lots of pumping. So what!!?? Anyone who has owned and used Coleman products know all about pumping their stoves and lanterns, and it's no big deal, for goodness sake!!!! I'd bet that the early Polar explorers did not sit around the Primus stoves, and grouse about having to pump it to get it up and running!!! NO, they LEARNED how to used it properly, and then were thankful when it do a great job for them!! SHEESH!!

    There are far too many "armchair/internet experts" out there today, pontificating about just about any subject you can name, and I'd wager a good many of the negative reviews for stoves, etc., have come directly from such know-nothing "experts"!!! :roll: :roll: :roll: :thumbdown: [-X [-X =; =; :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: Just my 'tuppence.... Take care, and God Bless!

    Every Good Wish,
    Doc
     
  17. DAVE GIBSON

    DAVE GIBSON Subscriber

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    wonderful post with just not a total break down of the stove but a cooking lesion tossed in.
    i do wonder with all those bits that looked like they are machined down very close and the O rings everywhere that it's really worth it in the long run.
    will it perform better than a 123 or a three leg kero burner when it comes down to making dinner?
     
  18. gunsoo

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    Great posting ,John !!

    :thumbup: :thumbup:

    Because of your kindness report about soto stove,

    i'm more learn operation about it .

    thank you !!

    Gunsoo
     
  19. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Thanks Gunsoo

    I learn a lot from your wonderful stove and excursion postings and always enjoy them very much.

    All the best,

    John
     
  20. snwcmpr

    snwcmpr Subscriber

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    Back here again, a very good post. Thank you John.

    Ken in NC