Hello, I have a 1200 (M I believe) that I cannot seem to get a consistently good burn with. I had been getting a decent burn, blue flames at the burner with no mantel or glass, but invariably over time the mantel darkens, light lowers, and the flames are orange, often with a halo outside the mantel. I _now_ have a brand new jet & needle and "J" tube from Fogas, new burner and burner cup (not sure of the names for these but both are newer white/high-temp ceramic) from elsewhere. The burn is worse than ever, with large flames outside both Valor 200/300 and 300/400 mantels. And in some cases the J tube is getting red hot. I've tried 14mm between jet & tube as well as the 250/300 setting on the petromax wrench (think that might be 12, don't have it in front of me), there doesn't seem to be much difference for me with those. To me it seems like somehow too much fuel is getting to the burner. I have tried lighting with valve open, no pressure and spirit pre-heat (I like this way a lot) and then a few pumps once the alcohol is almost gone- so a low pressure in the tank generally. And I've tried full-on 40 pump use the pre-heater lighting as well. Neither gets a good consistent burn. For fuel I'm using the Harald Nyborg "gold" kerosene in Denmark, I have seen elsewhere that it should be adequate. I know this level of inconsistency might make diagnosis impossible, but I'm happy for any thoughts. I'm writing this away from the lamp for a couple of weeks (I know, how could I leave it??) but have plenty of pictures I can share. Thanks for any input. -ben
Welcome aboard! The usual cause of that problem is that the hole in the jet is enlarged or the jet is loose or both.
Unfortunately I don't have much helpful advice but will just mention that if the J tube gets that red you should turn of the lamp immediately. At that temperature it is getting close to damaging the brass. A long shot could be that the preston loop is blocked.
You can try smaller needle/jet set - 150CP instead of 250/300CP etc. To verify this issue try this: Have fun
I think the clue lies in the J-tube glowing red. I've had similar issues with an Optimus 930 in the past. It would glow at first, but after about 10 minutes it would go dimmer. When I removed the top hood, it started glowing again. The problem was the J-tube. When I put a problematic J-tube into a working 930, it went dimmer, so the J-tube was definitely not good. I then replaced it with a new J-tube and it was fixed. To determine if the problem is with your lantern, try removing the top hood when the J-tube glows red. If you remove the top hood and let it light for a while, and the glow subsides and the glow returns, I recommend replacing the J-tube. If not, the suggestions from others may be effective. I hope your lantern lights up properly.
I too have had this issue with an optimus 350. No amount of messing would fix it, but a new j tube did the trick. This for me is one of the mysteries of these lanterns.
Thank you all for the responses. For the record: The J tube is brand new. The jet is brand new (though not a 150 size- I'll order one) I have quadruple checked that the jet was tightened well since I also thought maybe air was getting in or vaporized fuel was squirting out of a gap. I also tried copper grease since I saw that mentioned elsewhere on the site. No change with extra tightening or with the use of grease. I'll try the "under water" test when I get back, that sounds like a nice easy one. If it were a blocked preston loop, would the only fix for that be replacement? Thanks again, ben
@ben hall Copper grease does not work as a sealant - ask me how I know "Under water" test indeed works when performed as described above. I used blue (medium strength) threadlock to seal the leakage and it worked. A muffler cement recommended by others, may be a better idea, but I have not used it so far. Cleaning Preston look - you have a nice, new thread regarding that subject here: How to clean a Preston loop? "Fire ball" and "red hot J-tube/mixing pipe" is not an unusual problem and it has been written quite a lot on the forum about it. Seems there may be many reasons for it, but the most obvious were listed by Jeff in his post above. Sometimes it is even enough to put the inner casing a bit askew and problem occurs. There may be other reasons - check that thread for example: Ditmar MAXIM Type 506 -Problems and solutions-
