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M-1950 basket cases

Discussion in 'Military' started by presscall, May 23, 2012.

  1. presscall

    presscall United Kingdom Subscriber

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    I say 'basket cases' but they're retrievable. (Mouse-click the picture and it should fill the screen)

    1337804095-1.JPG


    The one on the left, a Fiesta branded example from 1981, I'd had a notable repair session on once before ...

    M-1950 and Wile E. Coyote moment


    1337804216-5.JPG

    Now, it was up for repair because of incontinence - wouldn't switch off - telling me I really should have replaced the nitrile 'pip' in the regulator on/off control mechanism, having gone to the trouble back then of removing the valve and stem from the tank.

    I'd since also managed to get hold of a new-old-stock windshield/pot rest ...

    1337804110-3.JPG

    ... so while I had it on the repair bench I could swap the new one for the badly-mauled example it came with

    1337804103-2.JPG


    The other one's of Wyott manufacture from 1974

    1337804208-4.JPG


    On Coleman 500's, getting the fuel/air valve stem and regulator control out of the tank is easy enough - clamp the control valve in wood-lined jaws of a vice and twist the fuel tank anti-clockwise.

    On these, the smaller diameter fuel tanks offer much less torque and the thin-walled steel makes them prone to denting. Something of a hassle and I daresay playing a blowtorch on the valve first (having purged the tank of fuel with soapy water) would help break the thread lock

    (Again, mouse-click on the picture and it'll enlarge to pick out the details)

    1337804223-6.JPG


    Curious that the Wyott tank has tapered threads cut into the whole depth of the mounting boss but the Fiesta's doesn't

    1337804231-7.jpg


    Jeff (Knight84) has posted some masterly details of the 'internals' of these stoves, but here's the valve and fuel/air stem

    1337804241-8.jpg


    Users tend to focus on the non-return valve 'pip' as safety-critical and they're right, since a failure of the seal there sends pressurised fuel up the pump tube and if that happens when the stove's lit, a fireball is inevitable.

    However, the sprung-loaded shut-off valve operated by the control knob (all the way to the right to spike the jet with the cleaning needle and shut off the fuel supply) is a vital seal too. If the seal fails with the stove lit and at operating temperature, so shut-off isn't possible, it's just a case of running the stove until the tank's out of fuel - a two or three-hour wait. If it fails when the priming charge is lit but before the stove's hot enough to vapourise the fuel, hopefully it would get into its stride before engulfing itself and its immediate surroundings in a lit pool of fuel, but that's a possibility too.

    On these examples, the seal on the Fiesta was rock-hard and on the Wyott, was spongy and breaking up. On the grounds that I wanted to 'fit and forget' these components I used viton replacements

    1337804249-9.jpg

    I used viton replacements for the non-return valves too

    1337807872-9a.JPG


    Pump assembly, with a replacement seal

    1337804257-10.jpg


    A recent post about M-1950's queried that gap between upper and lower pump cap components. This picture sequence shows that with the gap closed up, less threads are left exposed to grip the tank mounting boss and make the seal, so it's best to keep the gap as intended

    1337804266-11.jpg


    For now, the Wyott gets assembled and fired up. A fuel and airtight seal isn't dependent on the thread sealant ...

    1337804278-12.JPG


    ... the tapered threads take care of that - but it lubricates the joint when it's being tightened up and helps in orientating the control spindle to the right location mid-way between two windshield/pot rest mounting bosses

    1337806802-12a.JPG


    Niggles about the non-return valve not being bullet-proof like the lockable Coleman pattern are more than made up for by the sheer satisfaction in operating one of these stoves.

    Perfect!

    1337804288-13.JPG

    1337804298-14.JPG

    1337804309-15.JPG

    John
     
    Last edited by a moderator: Jul 2, 2015
  2. Rick b

    Rick b United States Subscriber

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    Hi John a good turtorial and interesting post as always. I missed this
    "A recent post about M-1950's queried that gap between upper and lower pump cap components. This picture sequence shows that with the gap closed up, less threads are left exposed to grip the tank mounting boss and make the seal, so it's best to keep the gap as intended" guess I have to look more closely at mine.

    (Also, we have an Army surplus store here that has the pot supports, not sure of the price but if anyone else needs one just let me know and I can find out).
     
  3. linux_author

    linux_author United States Subscriber

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    Excellent work and photography as usual! thanks!

    willie
     
  4. DAVE GIBSON United States

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    Super!!..i was lucky enough to get one that worked right out of the can.replacing a pump leather is a big deal for me---
     
  5. presscall

    presscall United Kingdom Subscriber

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    Got the other one (the Fiesta) reassembled this evening. Unlike the Wyott, this had the pump rod/tube storage space kitted out with a spare generator, pump cup washer and pump to tank seal.

    Washer and seal are unusable but the genny's handy to have

    1337974513-16.JPG


    I'd loosened a lot of sediment in the fuel tank wrenching at the generator body and swilled it out with methylated spirits. Looking at the flame colour, I guess it'll take a couple more tanks of white gasoline to clear out the residue

    1337974522-17.JPG

    1337974531-18.JPG

    John
     
    Last edited by a moderator: Jun 26, 2015
  6. geeves

    geeves New Zealand Subscriber

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    Sorry to open an old post but my SMC made m1950 has started to play up. It ran dry on me but when I refueled it it wouldnt run right. Indications are that air is getting mixed with the fuel at any setting except off. ie fuel spitting out the jet cold and if you do get it running you have to pump constantly. It not a leak at the fuel cap I left it pressurised for a week with no noticeable drop in pressure.
    Looking at the picture well up this thread it looks like the issue could be in the fuel pick up but I cant get it to budge. The stoves also full of fuel which possibly doesnt help. How do you empty these stoves?
    thanks
     
  7. 8R Pete

    8R Pete United States Subscriber

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    Any source for the valve? Would a Coleman 500 fit?
     
  8. presscall

    presscall United Kingdom Subscriber

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    Ah, the joys of the new forum's 'alert' facility!

    @geeves
    Your post back in 2013 got overlooked. Don't know if it's still an issue or maybe you sorted it ages ago? I found it tough to remove the valves out of those two, but they budged eventually - clamped valve, turned tank with an improvised strap wrench. Sounds like a fuel pick-up issue.
    @8R Pete
    The Speedster valve? Different design altogether.

    image.jpeg

    John
     
  9. fyrwokr

    fyrwokr United States Subscriber

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    Great information. I have a handful of these great stoves. The only one that gives me grief is the Fiesta 1980's model. That contractor had some quality control issues. It really never worked good and it of course is used for display.