Hi Ken, Not me that is for sure. @presscall, John and I has some lengthy conversations about the Muka pump. John is the one who did the work and discuss the short falls of such a complexed pump. He is the one that deserves all of the credit. Cheers, Norman
@presscall , Hi, John, Well, whilst down in the HH looking at my Prabhat stove, I dug out my Muka Soto, too. Just affixed it to the fuel bottle, and gave it a try. IF I left the control knob in the down position, when turning between stop, start, run, air, no leaking occurred. If, after having pulled up the knob, and set to the start and run positions, no leaks occurred. If I pushed the knob down, before turning it to "air", then pulling it up, again, no leak occurred. It was only when I kept the knob in the up position as I switched over to "air" that the leaking took place. I wonder if it would be best to always pop the control knob down, before moving it to "air", then pulling it up again to engage and allow the air to escape? Did you, and/or Norman have leaks whilst actually running the stove? Did you test it again with the knob down before moving to "air"? Unfortunately, I cannot locate my Muka instructions, at this time, and thus don't recall if stipulation was made for popping the knob down, before moving it to "air". You comments will be eagerly read, later on today, or tomorrow! Take care, and God Bless! Every Good Wish, Mark
@Doc Mark Hi Mark. No fuel seepage is acceptable whatever the control knob sequencing or setting. It simply shouldn't leak in any circumstances, period. The 'air' setting is the severest test of the seals in the fuel/air barrel assembly since full bottle pressure is released in a very short period of time and it's then that what I believe to be the 'weak link' seal that I identified on the barrel spindle allowed a fuel haze through in the pump I worked on (Norman's) and, I suspect - though I haven't yet dismantled it - in my original pump also, which displays exactly the same phenomenon in the same circumstances. It seems small comfort to know that the fuel leak occurs when 'air' is selected and shut-down of the flame is imminent, or for that matter that the leakage is small and vapour from it is perhaps unlikely to ignite at a hose-length distance ... unchecked, in the way of seal failure the leak could worsen and progress to one that does ignite, surely. John
@presscall , Hi, John, I agree with you, and will put the Muka on hold, until this is sussed out, and a good, reliable fettle is discovered. You, my friend, as the perfect person to undertake that, as you have, and I'm very happy about that!!! Well done, all around! Take care, and God Bless! Every Good Wish, Mark P.A. John, I may have misunderstood where your leaks are taking place. Is the pump actually leaking, or is the fuel leaking from the stove? If the fault is from the pump, mine is not leaking, at all. The stove, however, leaks fuel when the knob is placed in the position you have shown. Right now, it's cold, windy, foggy, and raining outside, but as soon as this storm blows over, I'll retest my Muka, just to make sure mine is also leaking from whence yours are. Thanks for clarification on that. I may have misunderstood.
@Doc Mark Mark, I took some photos of the leaking pump to clarify. Fuel bottle pressurised to the point where the pressure indicator red line appears. Control knob pulled upwards, ready to turn to 'Start'. No leak yet. Started up without a leak, set to 'Run'. Still no leak. Ah, now there's a leak. Safely shut down. The stove hadn't been lit, I placed it in a shallow bowl to catch the fuel out of the jet during the test as I suggested you do when testing your pump. What's noticeable is that the leak appeared when the control knob is very slightly 'rocked'. Now that's not misuse, since it's inevitable that the knob takes some sideways, and not just axial, finger pressure in use. Nothing more than that, and it leaked. Not acceptable. Therapy after that. I indulged in enjoying the relative simplicity of my MSR Firefly to brew up with. 'Dog bowl' windshield removed for the photo. John
@presscall @snwcmpr @hikin_jim @Doc Mark @teckguy_58 I just wanted to add my similar experience with the Muka pump. Last year while testing a stove I bought on ebay I noticed the fuel puddeling around the control knob as pictured above. It was during a simmer test with the control knob between low and air. Not having experienced this before I called Soto and they sent me a replacement pump which happens to have the new aluminum knob. About the same time another pump became available on ebay and now resides with the stove. I've saved the replacement as a spare if I ever need one. If someone would like to play with my original pump which I had disassembled let me know. Mike
Please forgive the thread resurrection. First of all, I want to add my congratulations and thanks to John for figuring out + solving this issue and documenting it in his usual exemplary fashion. Next, thank you to CCS as a whole for being the incredible, generous, kind, sharing folks that you are. Tangentially related to the control knob on the Muka, the same basic idea of the axial movement of a shaft through an O ring is used on many diesel fuel lift pumps. A similar O ring rides on the rod that actuates the pump, and separates engine oil and diesel fuel: (Couldn't the photo I took when I rebuilt my lift pump, instead I borrowed this one from Greazzer on the Peach Parts forum: http://www.peachparts.com/shopforum...-rebuilt-lift-pump-fuel-pump-om616-om617.html) Properly implemented, the basic premise is very sound. It's a shame Soto didn't consult with Bosch or with John before putting their pump into production.
Hi everyone, I have a soto muka with the metal control knob. Purchased Feb 2017 and used when new a few times and worked well. Went to use for a trip about a year or so later and didn't work, no fuel or air would run to the stove and could not release pressure in the tank. At the time I checked warranty and it was out so opened up the pump and found the two small air and fuel line o-rings had no hole in them (I think they flattened out and blocked the hole), but did not have any spare ones and for some reason soto do not sell spare o-rings. I put the stove away in disappointment. I have now got it back out and trying to find if soto will replace it for me even though it is out of warranty. Anyway I have opened it up again and going to try get o-rings online and see if i can repair. I have posted a few pics for reference with o-rings sizes I have measured but. If anyone has brought o-rings for this pump and knows the correct sizes that work please let me know.
What an interesting and educational post! Thanks to John and all the others involved! I own a Stormbreaker since 1 year (obviously with the new, aluminium knob-pump) and use it regularly, I put around 15 litres of automobile petrol through it in this time. Are there any more observations on the leakage with the new pump? BTW. When not in use, Soto recommends storing the pump clean, not in a filled bottle. They say it wears the parts out. If anyone has use for it, I could scan and post the manual for the Stormbreaker.
Oh, another observation: I just went off to test that simmering tweak on a position between Min and Air, which John and Norman have stated. This does not work on the new Stormbreaker pump! The gap is too large, when the air strats streaming there is absolutely no fuel flowing. So obviously yes, they have slightly changed the design.
Just wanted to chime in. I have a new Soto liquid fuel pump and I tore it down cause the o-rings havent been lubricated since leaving the factory maybe 8+ years ago and I noticed some resistance when actuating the Control Dial compared to my other soto pump. Mine is the new variant with the metal knob. Surprisingly enough, mine has 2 o-rings per fuel/air inlet. Also, the best way to remove the spring stoppers is by threading in a long machine screw with the correct thread pitch and pulling it out vs. using steel cordage. My biggest issue is the "wax seal" they put on the air/fuel inlet tubes. You need to break this seal to remove the air/fuel components. So potentially if you dont reseal it the same way, you may have terrible leaks of fuel in your airway or vice versa.
This is pretty unacceptable as it makes servicing it even harder than it already is as you need to melt a fuel safe wax* around the tubes.
Hiya Soto Stove owners, I am in possession of the Muka, Windmaster and Stormbreaker. Upon contact with Soto by email, I have experienced very good customer service, meaning supply of spare parts on request. I was happy to pay for parts and shipping, I was not asked to pay anything. If that is not good customer service, then I am lst for words at least. Cheers Simon Foxxx New Zealand
hi all, have just purchased a stormbreaker for motorcycle camping, just used a couple of times so far and no issues yet reading here i see the pumps for the muka and the stormbreaker are interchangeable but there do seem to be improvements in the later, silver-dial, stormbreaker pumps, so here are a couple of pics first is a close-up of the production date stamp on the back of the silver-dial in the left of the pic above you can see the 2 clear pick-ups exiting the black plastic here is a close-up of the 2 screws securing the tubes into the body by contrast in the earlier photos of the break-down of the black-dial soto pumps, it seems the pick-up tubes are glued into a slightly different
just bought a 3rd? hand muka that was missing the fuel pick-up tube in the pump the plan was to use a fuel pick-up line from an old MSR pump took a bit of pulling but eventually the line came out of the MSR pump and was pushed into the muka pump at this stage hoped it was good to go, so put pump into filled fuel bottle and pumped until red pressure ring appeared then started unfolding legs of burner head and pulling off black caps etc. looked back at the bottle and noticed pressure tit had disappeared and fuel was dripping out of bottle, seemingly from the back dial base hmmm....looks like the pump needs to be at least partially pulled apart, fortunately great pics in this thread.......soto seem to suggest complete pump replacement with pump needing more work decided to test burner head so took old muka pump out, put new stormbreaker pump in, pumped up bottle again and connected muka burner during connection noticed that the free turning hose to burner connector was quite loose...... turned pump valve to start and fuel started leaking from the generator joint.... tried to tighten but it was already tight seems the 3 o-rings on the generator connector are too worn....soto seem to suggest changing the whole part along with the generator the fuel-line to generator doesn't really need to pivot and it on the newer stormbreaker it doesn't at this stage have packed it all away until i find my o-rings, fully read this thread and then find the time to have another go
