I think so. One jet for all fuel is... just a marketing point and it works as she declares but Not in efficient way, of course. Even the user does Less Throttle(reduced fuel supplying) using Kerosene, it still doesn't very good, the jet orifice size is still same, so the vapored fuel injection is not very in perfect condition. Butane with 3min is a way too boring, if you tried as inverted position, it might be better I am sure... Sum up, in my opinion, the oem jet has too big orifice for Kerosene, and other similar heavier fuels.
I find that in the case of the Nova+ I can close up the fuel bottle valve a little to prevent pulsation. On the Polaris I'd say it would be an issue of relatively "high" pressure in the tank causing oscillation, in my experience a little less pressure in the bottle helps if I plan on simmering with it given there is no valve on the bottle to control flow. Having very low fuel pressure seems to alievate any pulsation from it. You can gradually depressurize the fuel bottle by inverting it for a few seconds then putting it back into the normal position, letting some of the air out slowly when it gets fed into the fuel line without having to shut the stove down and do a messy depressurization of the bottle. In regards to burning kerosene in the Polaris with the non optimized jet: I've found adding a little bit of isopropyl alcohol can make it burn closer to the fuel air mix ratio of white gas. Perhaps this can be used in a way to trim back the fuel mixture from being a little rich. I also find that the Nova+ tends to be a bit of a better burner with kerosene without a silent cap in contrast to the Polaris. I've had good luck with this to the point that I can get super blue flames without a single bit of orange streak if a sufficient percentage of alcohol is added.
While I've managed to get moments of non-pulsating from the Polaris, the moment a pot goes on it's like a helicopter. Only canisters run smoothly. I've tried all the tricks (spreader height, MSR fuel tip, no fuel tip, teardowns, low pumping, high pumping, etc) and I just think the stove is a dud.
I think it was Odd who told us the trick of changing the flame plate height to change the fuel/air ratio. My Nova was helicoptering until I raised the flame plate for kerosene and lowered the flame plate for white gas. No more helicoptering.
Mine only really pulses when I over pump it and then I just turn down the fuel flow at bottle or on my older Nova's just let it burn a while and the pulsing goes away.
I might go back to it and give it another go, but I feel like I got the "full suite" of flaws that lead to the helicopter because no amount of tweaking has tamed it. I even tried swapping out the lindal connector with a Vega and popped in shaker-less XGK jets of various sizes. Works great on canisters, said nobody happily. light touch with flow didn't do it either. I suspect it has some kind of manufacturing tolerance issue that plagued Optimus throughout its pursuit of off-shore savings.
You know, a millimeter or so has made it more of a turboprop and less of a chopper. I can live with that. Is it fair to say that's more of its sonic profile than raw heat white noise of Dragonfly or XGK or is any "chugging" sound a sign of bad air-fuel ratios?
I never experienced a pulsating problem with the primus Omnilite. That had different jets optimised for the different fuels. I finally decided to spend some money on the Polar Dawg silencer and this has all but cured the pulsing as well as reducing noise and improving simmer control . Performance with canister gas has improved too, this used to take a full minute longer than other fuels to heat half a litre. Now the same as the rest. It also had poor simmer control with this fuel, having a tendancy to go out altogether when turned low. Not any more. The only drawback is the longer preheat time particularly with kerosene, this can be as long as a minute and a half to two minutes. By which time, your cheap gas stove would have boiled the water for your brew. The cap also takes a long time to cool. So has to be knocked off and quenched.
@Tacho D I have the Omnilite II and it runs beautifully, so that just makes the Optifuel’s performance more upsetting, but the reminder to try a PolarDawg is a good one. It’s just disappointing that one needs to find aftermarket parts to get the most expensive modern MF stove working respectably.
I did eventually put a Primus silencer on the Omnilite too. That benefited greatly from the conversion too. I wish I kept it.
Hello, just only my opinion, I think Optimus Katadyn's recent MF stoves are not quite well made in several point of view. Thankfully we still have some alternatives Primus and MSR. And Optimus might not want to keep the model line up for MF, she wants to reduce for that cost?, maybe the turnover is not happy for her?, Sustainability issue?, Idk anyway now only few models and Hiker Plus was discontinued. Hope Primus will have any of self-jet-pricker like other two's, but I don't think she will do. Jet prickering is insane (for me) in today's multifuel stove. MSR/Optimus does well, If I don't want that feature, can be removeds simply, but who doesn't? meh...
@Odd low throttle doesn’t change the pulsating, and seems to even make it worse, and good point about the full throttle waste. I’m never in a hurry, so the principle of a optimal fuel/speed sweet spot (just like with cars on highways) has always been in my mind, but it’s also always seemed more dramatic with the Polaris. Boil times are around 5:45-6 min/L anyway, so it’s never been a speedy one. Thanks for checking yours. I ordered the PD cap simply because I’m curious how great of an impact it might make! @Yun124 it does look like Optimus is cutting down on all MF stoves. They face still competition from … themselves. Who buys a new Hiker + when so many very good 111s still exist on eBay? You have a very small niche of people who want that nostalgia I imagine. I don’t even understand why they still make the Svea, except that some people don’t feel comfortable with a refurbished classic one. Before I started to love these stoves, MF didn’t matter at all. A Simmerlite was perfect for my kind of backcountry trips—light, quiet, could simmer with thoughtful pumping, and weighed half of a MF. That’s still the stove I take when I’m just being pragmatic about weight/versatility on a trip, and the saddest discontinuation of a stove in my opinion. As for Primus mine also had a flaw. The Omnifuel II (I mistyped OMNILITE above) I have warped at the bell from the spreader—not enough to send back, but I was upset after seeing that too and had to adjust the spring. You wonder how many people without a passion for stoves are willing to fiddle with things like this before jumping ship to canister-only.
I've also Omnifuel II, which is the last revision (afaik) - it has the modified spring, a little longer than revision 1. I read one web blog that described about it. Primus knew the spring was designed wrongly so it had too much tension. Very frankly I don't know why Primus did it wrongly, it was very easily found problem before launch the new model, but she had not relized it from the internal testing, if it existed. For the stove world, The elder the better... *regarding your distorted burner bell, you may need to email or contact Primus USA dealership so I am very sure she will send you free of charge, the new burner bell and spreader as the revision 2. Omni series has the lifetime (really? anyway) warrenty, and I think it works.b
I will defend Optimus for my late model Nova. Beautifully made, runs very well, and I like the much simpler bayonet fitting to the pump. As for customer service, the other day I finally actually opened up the expedition kit I bought a year ago. My inventory found it was missing two pieces. It was late in the evening when I sent an email to Katahdyn customer service. First thing in the morning I received a reply. Since they do not sell individual pieces, the next day they mailed off another full kit to me.
Hi folks, Well, it turns out that my previous post in this thread about fixing the pulsing of my sister’s Primus Polaris this last August was wishful thinking. But now I think I have a solution, albeit with a sample size of one. Who knows if it would work for others. In checking out an unrelated problem from our last snow camping trip I did a few test runs in the shop and the annoying helicoptering was still there. I tried most of the things suggested here but none really solved the issue over a range of flame heights. At least with this particular stove, paultee’s comment about some sort of manufacturing issue made sense. And Lennart F’s comment about fuel restrictors in old blow lamps gave me one idea. I’ll skip all the things I tried and just stick to the two things that seemed to have worked. I gather that one of the functions of wicks in Svea / Optimus burners is to dampen fluctuations in the flame. So I made the equivalent that fits inside the fuel line using Kevlar thread as the wicking material. (I’ve used the Kevlar wick I made for my Optimus 99 since July; it has worked well.) Here are a couple of shots: And here’s a shot showing how it comes out if it needs to be removed: grab the Kevlar thread with a hemostat. Just enough sticks out but not enough to interfere with the seal. I’ve removed and replaced it several times just to make sure. Just this addition modestly reduced the pulsations. It seemed to me that a peculiarity of the geometry of the burner was a primary cause of the pulsation so the idea was to change something that would influence the gas flow. A number of things I tried didn’t work. However, I remembered that in my recent experiments with flame spreaders, I found that the thin stainless steel one shown in this post caused some minor rapid pulsations when the flame was turned up full. Flame spreader design choices? The Polaris has a thin stainless steel flame spreader but it is almost flat. I got up the nerve to dap it into a modest dish shape as I had done with the one I made for the 99. That along with the wick nearly eliminated the pulsing. I began wondering if the material choice (stainless steel with its poor heat conduction) was also part of the problem. After my post above, snwcmpr said ‘try brass’ so of course I did and made one for the 99. I’ve been meaning to report on this too, but the result has been excellent. Compared to the stock 99 flame spreader, my latest one has a much deeper dish and is quite thin – 16 ml vs 40 mil. With this in mind, I made a similar flame spreader for the Polaris. It turns out that the center circular area is the same size (1.2” dia) so I could use the same mold for dapping. A couple of pics: The result, although not that mystical perfect flame, seems pretty acceptable but the proof will be during the next snow camping trip. There is little or no pulsation throughout a typical range of flame settings. Here’s a shot in operation. What’s interesting is that the cooler spot from the jet is now centered in the flame spreader whereas before it was pushed say 3/8ths of an inch opposite the control valve resulting in an uneven flame, why I can’t guess. With the brass flame spreader, the flame is concentric. And here's a short video
The idea of some sort of damper inside the fuel line makes sense as I think this is where fluctuations occur in fuel pressure causing the pulses. I think this is the reason for the rhythmical tapping I hear inside the fuel bottle during pulsing, probably due to the end of the fuel line hitting the side of the bottle. Wirth trying.
@Larry_R This is great! I was starting to feel like a nut for thinking there was something simply flawed in the design of the stove (while fuel tampons and spreader tweaking did a little it was never pulse-free). The Polar cap addressed the spreader issue, which I assume is why it seems like a fix for so many people, but your attempts to tackle the actual source of these nuisances is impressive. Mine shares the same slightly off centre (opposite valve) quirk yours has and it's also gotten under my skin (changing jet didn't help), but I won't be making a new spreader anytime soon. The kevlar wick, however, is a trick I'll copy from you! I also enjoyed that using Optimus' "old methods" of wicks and brass did the trick. One other thing: I found a slight improvement on pulsing with the newer sintered copper filters Optimus uses now instead of the white pips, so there's another old vs. new solution.
Hi guys, this just to mention that putting my wick in the fuel tubing in the fuel bottle did not help. it makes me suspect this scenario: when a pulse occurs and the flame momentarily increases, the pressure against which the jet must operate goes up. This slows the gaseous fuel flow slightly and the flame goes down. Now the pressure outside of the jet is lower and that allows more fuel to flow, creating another pulse. The wick near the jet probably dampens this more or less harmonic oscillation. But that does not seem to be the entire story in that the custom flame spreader helped a lot too.
I dropped in a spreader from an XGK II as it’s dramatically more concave, a decent size match, and also heavier duty. It created a more consistent flame. Does seem to support your reworking of your Optimus spreader. That’s just one anecdotal instance, but as it’s non-destructive maybe someone else with these two stoves could weight in with observations.
