@Larry_R I do have one more question. Did you try different jets? I've found the Polaris is very picky. It pulses more on an old Optimus Nova/Polaris jet more than one that comes in the updated service kit (the updated one has the sintered fuel filter instead of the white foam one). I actually fished out the old jet and there's a slight bevel on the topside of the newer one that's absent in the old jet, which is simply a hole. I can't imagine they just opted to add the conical exit for no reason!
@paultee Hi Paul, I didn't try any other jets; don't have any other than for my own stove. Interesting your comment about the bevel or chamfer on the newer jet. Thinking that the sides of the screwdriver slot adjacent to the orifice might be somehow affecting the jet of gas, I ground some of the metal away with a small burr but not getting near the orifice itself. It didn't make any difference. I wonder if the following relates to the Polaris being picky about jets: to the best I could tell, the orifice was clean and perfectly round, seemingly all OK. But I decided to check the diameter of the hole using short bits of stainless-steel wire, 12 mil, 13 mil, 14 mil and 16 mil. I didn't want to have the wire damage the jet so after nipping the sections off I spun them up with a small collet chuck against a hard honing stone to create something of a bullet shaped tip. When I got to 14 mil what seemed like a hard little ring of crud popped out. (I didn't clearly see it however.) After that, the 16 mil wire went in easily but still with a fraction of slop. A 17 mil drill bit seemed to want to go but I did not want to press my luck. This is an old stove that has had a lot of use without much maintenance. After doing that, fewer pumps were needed to get a nice flame.
Here's a pic of the newer vs old jet. The newer one is the one that's a bit off centre where it hits the spreader, but it also looks like the chamfering is uneven. I consider that a much lower-level issue than the pulsing which is consistently more prominent on the older jet with years of use. NEW JET: Old jet: I'm glad cleaning helped. I am curious about whether your jet looks more like the newer or the older one.
My sister's stove has the older style jet per your pics. However the orifice does not seem to have any chamfer at all unlike your picture above. My guess is that the purpose of the chamfer is to prevent damage to the opening of the hole which would disturb the laminar flow as the gas exits.
The chamfer in machining serves several purposes. 1) A firm and solid center drill is used to start the hole so that the smaller drill has a place to go, and does not 'walk'. A more precise location is obtained. 2) If the depth of the center drill is set deep/wide enough, a chamfer is left, and the hole is clean, as in without burrs. 3) It 'breaks' the edge so it is not a sharp edge. I am not sure why the chamfer works in a stove jet, but I imagined it is a cleaner (no burrs) exit of vapor, and thus there is less turbulence. It would be an added expense in the manufacturing process. Unless needed, it would not be performed or designed into the part.
I don't know where I picked up 'mil' for thousandths of an inch. Maybe in my dreams? I think I got it from my Dad.
I don't know what the size of the jet is as manufactured. As a check I found that 0.012" SS wire was a close but not tight fit in my spare Optimus 99 jet. Once the wire was through the hole, the jet would spin easily on it with no wobble. The old Polaris jet would wobble some on 0.016" wire. This is an old stove with a lot of use, including a lot of melting snow in a humid environment. And my sister lives next to the salt water. Could it be that the jet is really worn and or corroded? (It is corroded on the outside, unlike my Optimus jets.) Can anyone suggest a source for a new jet? (A late Xmas present maybe.)
I bought an optimus polaris omnifuel back in November and ended up here because of the pulsating issue with mine as well. Ive used an msr dragonfly for years with only a few complaints but was attracted to the polaris because of its flexible fuel line, metal pump and tighter pack up. I did like the idea of not changing jets switching to kerosene as I fly helicopters in the bush and there is no shortage of jet fuel at my disposal should I run out of naptha or Aspen 4. Ive noticed the polaris is much dirtier than my dragonfly was after significantly less use using the same fuel. The pulsing started on mine after a short while and so I pulled out the jet to give it all a good clean. That was when I discovered the super flimsy burner plate and have struggled to keep it even and centered since. I have noticed mine has the chamfered jet. Looking at the jet when its pulsing occasionally a sideways flame would shoot directly out of the orifice and would only go away if the valve was lowered then brought back up to keep the flame on the burner plate. I decided to pull the jet yet again and this time noticed that although the cleaning needle easily fit through, the orifice was not perfectly circular looking through. I scraped away at it with the needle and I think I got it rounder by cleaning some carbon or something off. After reassembly its sounding much better. I have noticed a bit of flame shoots out the side of the burner though where the slot for the burner plate is. I also overheated the stove when I first bought it, testing isobutane inside with the warm bottle inverted. The whole thing was bright red and it looked like gas was burning from the sides of the jet when I shut it off :O worked ok after but that wasnt long until the start of my pulsing. My quest for the perfect stove continues. I wish the soto stormbreak was both more reliable and available.
I’m glad the jet was the likely culprit for you, too, but equally sorry you had to go down the same road. My biggest issue now is that Optimus spare parts are hen’s teeth in Canada (possibly beyond?!). That disqualifies it as a serious option long term as I can’t easily acquire a backup jet or flame spreader by walking in MEC or any major Canadian outfitter. As for perfect stove—there isn’t one, but I’ve settled on the perfect STOVES: Backpacking: Simmerlite ideally, but Whisperlite INTL otherwise, and any good canister unit like a Crux or Pocket Rocket pro for cooler weather. The combo still weighs less than a Polaris alone. Canoeing, especially with a bigger group: Dragonfly and the Vega as secondary. I’m a huge fan of the Vega and will happily take the 100g hit backpacking sometimes too if I know someone who hates liquid fuel is joining me. These are just the stoves I landed on through a combo of subjective experiences and the fact that in Canada we have cheap Coleman fuel everywhere, and canisters keep shooting up in price. Nearly all will do the trick if you know how to field-maintain and bring backup parts, but MSR wins in North America for simplicity and access to those. In fact, some of the best prices on spare parts I’ve found on MSR kits and pumps were on dusty shelves of northern outfitters. It’s funny you mention the Soto, which I once dreamed could do it all, then saw the teardown of its pump on here and that dream died. Soto also doesn’t have distribution in Canada so you’ll basically be importing a stove you’ll never be able to find quick access to parts with (anything here is from third party sellers importing from Australia or its origin country, Japan). This is especially worrying as it has a limited service life generator (though apparently very long, but still, who wants that question mark). The only thing that never comes is a Jetboil. I had one melt entirely (later recalled so I got a replacement I never use), and have seen my other smaller Jetboil perform hopelessly in wind and cold while an MSR Windburner aced it. Many here have more experience with stoves, but that’s just my take! And if it sounds like I don’t like Optimus, absolutely not true: my favourite stove is a Swedish-made Nova I simply like too much to subject to the abuse of a long trip but will happily take on a low intensity weekend!
