I was thinking to change the jet in my Polaris. Does the MSR K Jet for the Dragonfly work? MSR part 419836
The jet thread pitch and diameter is the same as the XGK EX's XK and D jet but the MSR jets are too tall by at least 1/4"/6mm if not more.
I've tried them. Both XGK GK jet #419266 and X jet #419267 fit. You can find them in MSR XGK-EX Expedition service kits. GK jet aperture is the same or little bit larger than Optimus 0.32mm jet aperture. X jet aperture is just a little bit smaller. Yes, it burns a little better, like Primus Omnifuel. The jet cleaning needle fits thru the X jet but probably won't work while the stove is in use. I thought about filing down the X jet so it sits lower and also filing the cleaning needle just for the proof of concept that you can modify the Polaris but never just got around to it. As a sidenote, I agree with Odd, I think it defeats the stoves purpose. With Berniedawg or Korean silent cap it burns quality kerosene very very cleanly.
By chance have you tried the X/diesel jet in the Polaris with the greater height and seen any differences? It was something tempting just to hear about the results. I experiment with my stoves and seeing the Polaris is a little bit of a less than optimal performer in some conditions drove my curiosity as well, along with looking at silent cap performance variations: I have a Nova cap I tried using with the Polaris and found that it needed some time to heat up and still burned with a bit of yellow in the tips at some settings unless the burner bell was red hot. The cap also could get hot to the point that it glows a dull red but only under certain circumstances at high settings. I also have the Korean UFO cap but I have yet to test it with liquid fuel. It is as usual a bit sensitive to underburn but especially so at super low simmer settings. I will have to procure a BD Polardawg 2 cap later...
Yes, I tried it and compared boiling times and kerosene consumption with the original and the X jet but didn't record the exact findings. The X jet was slower but that's understandable: less fuel = reduced power. Here they are side to side: As with the original Nova, Nova+ and the current Nova, besides changing jet aperture, the only possibility seems to be raising the flame plate to try to optimize the clean combustion. Here's a few pictures, unfortunately I don't have videos. Both stoves are Polaris, the one in Trangia has original jet. X jet is in normal Polaris. Kerophile posted a thread where made a smaller jet for Nova, my experience is similar with this XGK jet. With PolarDawg2: And with original flame plates that have been adjusted (raised) for kerosene: Both have equal amount of fuel and pressure and are cranked to max, as was with PolarDawg2. The Nova cap, Dawg-A-Nova, has mass and it shows. It works best with white gas or similar fuels. With kerosene I wouldn't bother with it. Although, just for science I tried adding pure heptane to kerosene 10%-25% and it made a big difference using Dawg-A-Nova. The flashpoint was still acceptable, so it wouldn't ignite with a hot spark. As far as I know, all the Novas, past and present have had the same jet as the Polaris. The current Nova has the exact same bell dimensions as the Polaris but Polaris have smaller fins in the burner bell. Thus you can file down the Nova fins and have a Polaris clone. I like the PolarDawg2 so much that I converted one of my Hiker+ stoves to Polaris. Here's Hiker+ with PolarDawg2: The UFO cap was a little bit disappointment. The one for Polaris works better. The Korean version flame is bluer but I think the red hue from PolarDawg2 comes from the metal, Korean version is solid steel. It's more finicky and when properly adjusted, I think the combustion might be cleaner than PolarDawg's. Both are good. To arctic I'd take PolarDawg, Korean cap takes a little bit longer to prime. And couple more things I've noticed but haven't seen mentioned in any forums. The current Optimus jets have a quality problem. If your stove won't burn kerosene cleanly, try changing the jet also. The first jet I had was too large, the aperture was oval shaped. This was clear when looking through dental loupes. 3D printing services aren't producing exactly the same dimensions every time either. I have three PolarDawgs with different finishes and they have subtle differences, this shows somewhat in those above pictures. Hope this helps, I think with silent cap this stove really shines.
Much thanks for your detailed reply including all your findings! I was looking at the X jet and thinking of trying to somehow source a non-shaker jet after doing a quick test fit. I thought it was a bit of a disappointment that the expedition kit didn't include the non-shaker jets and had thought to contact MSR but seeing that indeed the X jet will happily run in the Polaris is a good sign. The pure blue flames coming off of those is a bit better than what I found with my new Polaris but my fuel was around 80% kerosene with a bit of white gas, charcoal lighter fluid and a tiny bit of alcohol in it. Weirdness of the mix aside that I'm trying to use it up. I was a bit disappointed by the performance on the Polaris since the same fuel had produced "pure blue" flames on a Primus Omnilite Ti with the Primus silencer. With the Polaris it seemed to need a bit of heating or I will see yellow streaks or yellow in the tips when it is running flat out and just finished with warming up for a few seconds after a preheat with the Nova silencer. From what I saw from your photos and your reporting it seems like the X jet definitely will yield good results. I thought the raised height would mess with the air mix ratio by causing it to run richer but it appears not to with flames that blue. I found that an alternative is a mix of white gas and charcoal lighter fluid does the trick in the US for reducing flammability for white gas as the CLF is some form of heavy naphtha here rather than kerosene. I will have to try out a new mix to see if the Nova cap does any better but I'm likely to get a Polardawg cap given the praise for it. I like the idea of it, especially with the centrally focused flame and I had originally gotten it out of curiosity for my Omnilite Ti which it was too big for. It fits inside a XGK EX but the burner bell isn't very round ("trigonal" is the best way I would describe it, it is still "round" but not perfeclty circular) and it would go into underburn easily at low power settings and stay there due to the bell not sealing well. Strangely enough the Korean UFO cap seems to be best paired with the Polaris aside from the issue with underburn on gas at very, very low output. Ouch. I did find that the "build" of the Polaris is a little less nice than all of my other MSR, Primus and Soto liquid stoves. Little things like the green paint chipping off the control valve and pump handle end were not too confidence inspiring. Worse comes to worse I may have to try the hypodermic needle method to "salvage" the jet into a smaller one if it is very oversized. I'll have to check with a macro lens or a microscope later to see if I have a problem jet which may explain the sight yellowing even with the cap under certain conditions. Again much thanks for your post, it was extremely informative.
This thread prompted me to check the approximate jet aperture sizes of older XGK kerosene jets and compare them to current Optimus Nova/Polaris jet. I used steel guitar strings as a gauge. MSR XGK shaker X jet, Optimus Polaris and MSR XGK non-shaker K jet Somewhat surprising but non-shaker K jet (#419251) has the largest aperture and it's not worn or enlarged, I tested two of them. 0.011" string was a tight fit to shaker X jet.
