Hi, I have a Svea 123. My dad bought it in the 80's, and it was the stove that came on all the backpacking trips I went on as a kid. It was always finicky and fussy, and often it didn't seem to have enough oomph, especially if it was getting to the freezing temps outside. And in the Canadian Rockies that happens 12 months of the year. So I recently acquired from my dad. He had retired it over a decade ago prefering to use a canister stove. I've played with it a bit, and in the house it performs great. But outside it is certainly anemic. So I bought an optimus pump and cap from Ebay. The first run with that setup in my yard earlier this week was great. It worked perfect, and even in just below freezing temps the pump made that thing into a rocket. So I took it ice fishing today to heat up some hot chocolate for my kids. It was windy out, but I got a bit of a wind break and tried to light it. It was taking FOREVER to prime, and took 4 priming cycles to get it warm enough to actually get a bit of a blue flame. I kept pumping that pump, and it would help for a few seconds, and then it would just go out. I fussed with it for nearly an hour, but I couldn't manage to keep it lit, let alone keep a good cooking flame. It was only a few degrees below freezing. My kids were pretty disappointed that they didn't get any hot chocolate. So once home I left it out in my back yard to cool the system down, and I tried again. With no wind I was able to see that flame kept on coming out of the pump cap. On the cap there is a piece right on the end that looks like it should take a allen wrench, except it's a 5 sided recess, not a 6 sided hex. So the one-way valve of the pump cap is letting out pressure, and that's why the stove wouldn't stay lit. Can this valve just be tightened? I don't have a 5 sided allen key, nor do I know where I could get one. Can this be fixed at all, or is this pump cap just defective?
So after doing some google searches on this website I found some pics that gave me a bit better understanding of how the valves in the pump cap work. So the long skinny piece that protrudes into the tank screws off. I screwed it off and I came to realize that the little rubber stopper in there wasn't returning up where it is supposed to be in order to hold pressure. The spring in there isn't strong enough to push it back in to place. So I cheated. I pulled out the spring and stretched it. That makes the spring a bit stronger. The temp outside is only zero celcius... right at freezing. But I left the stove outside while I cleaned the fish I caught today. So 20 min later I went outside and tried the stove again. It worked beautifully. The pump cap held pressure and not only did it light up, but it had a rocket of a blue torch flame. So now the stove and pump is in the freezer. I'm going to leave it ther until morning, then take it outside and see if I can get it to be a rocket again. I really really want to love this stove. I'd like it to be a go-to stove for winter outings, like cross country skiing, ice fishing etc. I know lots of you guys do use your sveas as your go-to stoves, so I hope I can gain that kind of confidence in this one. Next time I go ice fishing I'll have a back-up stove. Probably my soto micro-regulator canister stove, or if it's really cold, my whisperlite.
Yep. You discovered a major reason these stoves (not just the Svea) show the symptoms you describe. In addition to the weak spring you found, the "rubber" pip at the end of the spring will get hard with age and the washer in the cap itself can harder and not seal well. If the cap is an older used one, you might want to consider replacing both of those pieces as well. With a good cap you may find that the pump is seldom necessary.
My freezer is at -18C. I took the stove out of the freezer this morning [where it spent all night] and took it outside where it's a balmy -3C. The fuel took FOREVER to get warm enough to be vapour, but kept spewing out of the jet as liquid, so priming took a long time. But once it primed it worked very well. The cap held pressure and the stove was a rocket with a very strong blue flame. It was great. I might go out ice fishing again later today. If I do I'll try another "real world" test.
Same thing with a 8R here, when all the seals and springs are spot on, they're a delight. But self-pressurizing stoves have their cold weather limits, it's why I love my M1950 and Coleman 530 for witch's tit cold temps, a nudge or three on the pump, and lunch is served! Murph
Rubber tends to become rigid at freezing temperatures. (Remember Prof. Feinman's conclusions and demo of why the Challenger shuttle exploded?) You want to be double sure that both the valve rubber pip and the tank cap seal are made of Viton, and are new and fresh, if you plan on using the 123 in sub-zero temperatures. If weight is not a limitation, and you want to use a classic stove, try the Optimus 111B or 111T, running on kerosene (and use meths for priming). As far as I know, that is the stove of choice in Antarctica. Yonadav
Because the 123 is self pressurizing it is sensitive to ambient temperature and is more suited to warmer weather, above freezing. That said, replacing the fill cap gasket and pip with Viton ones, available easily on E-bay from "The Fettlebox" AND putting an insulating base under the stove and a windscreed around it will improve performance. For years I used a 1/2" thick by 8" octagonal piece of marine plywood as a base for mine. Don't paint or varnish it as bare wood is much less likely to slide on snow. The Optimus Mini Pump was not designed to pressurize the stove, only to assist in priming. Do not add more than three pumps when starting the stove. More than that risk overpressure and pressure release, bringing life to the 123's cognomen, "Swedish Hand Grenade". Which is quite an exciting thing to experience. Some of the symptoms you describe are those of a perished wick. There are myriad descriptions and pictures of 123 wick replacement on this site. Again an inexpensive and easy task. If you attempt this, note the position of the valve stem in relation to the lettering on the fount. It is important. A wind block is helpful as well, mine is a three sided alumin(i)um one hinged in thirds and acquired so long ago the information on it is in hieroglyphs. Almost any means of blocking the wind is helpful, from purpose made screens to a hiking companion laid on the ground upwind and the stove set close to him/her. I've also used a recently killed deer, my pack, and a pile of rocks cleverly placed at different times. All work, but I prefer my alumin(i)um one. The very best solution is using the 123 in conjunction with a Sigg Tourist Cooker. I've used the Sigg Tourist with my 123 for many years and use the plwood base under it for even more insulation from cold ground, ice and snow. No longer in production, the Sigg Tourist is to be found on Craigslist, in second hand stores or E-bay, usually at extortionate cost but sometimes a bargain presents itself. Keep looking and good luck. Gerry
