Hello All, What a pleasure to find a forum dedicated to pressure lamps! It is marvellous to see these great old lamps getting used and looked after! I have a couple but my question is regarding my Optimus 930 that I have used in my hut for years but of recent times it is giving me some grief. A little while ago I brought it out of the bush for a birthday, cleaned tanks, replaced pricker and a few bits but was unable to get the correct jet for it. The one I obtained from a camping shop in Christchurch has 300 stamped on it and since fitting it the lamp seems to be over-fuelling (mantle does not turn incandescent white and gets black from the yellow flames on the outside of the mantle). It is a 300CP lamp but I am not sure that is reflected in the number on the jet. The original jet I have for it is almost completely blocked. Could it be chemically cleaned as I can’t imagine a jet drill down to that size. In fact, what is the correct bore diameter for this lamp? Anyway, I would like to buy an original jet to be sure I have the right one. Can anyone point me in the right direction please? cheers, Zap.
Welcome, @Zapper. Your lantern sound like it is running too rich. 1. Have you checked that the nipple is not loose? 2. Your original jet can be cleaned. First soak the nipple in acetone, thinners or brake clear (or similar), then use a very fine wire (0.15mm) to clear the jet. See if replacing your original jet fixes the problem. Cheers Tony
I know they do call the 930 a 300cp lamp, but in reality the burner parts are all the same dimensions as for a 200/250cp lamp. Therefore a jet of this size will often work better. Are there any markings on the original jet? For reference, a 200cp jet size is 0.17mm and a 300cp jet size is 0.20mm.
Both of my optimus 930s have 200 marked on the jets and both work very well. As Tony said try and clean the original jet and see how it runs. Ian
Apart from chemical cleaning, heating a jet nipple to a dull red heat usually makes the blockage easy to remove.
Many Thanks for the replies and welcome. I'll lyk how I go on cleaning the original jet. Thanks for the specs as well. Will try straight acetone and wire (hmm 0.17mm is small) and if no joy then try heating it as well. Cheers, Zap
I have learned from this site that the smallest guitarstrings can be used as cleaning wire for the jet. So I use that to clean 150CP jets and preheaters on the bigger lanterns with preheater. Matti
That is a very thin guitar string <0.007" The lightest Top E string is usually 0.008" You might find a 0.007" as the Top G in a 12 string guitar set. 0.006" is specialist. What about acupuncture needles?
Acupuncture needles are cheaper than guitar strings - plenty on ebay sizes there are typically 0.12 to 0.3mm in increments.
Acupuncture needles also used as pricker needle replacement in various lanterns. Pay attention to correct diameter per lantern jet cp rating
Cleaned the original jet in acetone and replaced it. Same problem with over fuelling/cold kero giving a lazy yellow flame on mantle and subsequently carboning the mantle up. If it is cold/excess fuel then it could be the pricker shaft could be a loose enough fit in the gas generator tube as to let cold fuel past it between the in,et and outlet of the gas generator spiral. I doubt that is the case though as it does not have a seal fitted and so to be able to move the shaft through the tube easily it cannot be a fluid-tight fit. I am guessing there is always some leakage there but with the fuel taking normally taking the easier path of around the spiral and vapourising before getting to the jet. When I first disassembled the lamp there was a fair bit of burnt carbon like crap clinging to the pricker shaft and so would not be surprised if the whole gas generator was contaminated. So I am now focussing on the spiral part of the gas generator. I removed gas generator from lamp, fitted a blocked jet to it, inverted it and filled it with acetone. Left it soak for a few hours and then tried pushing a zip tie through from the top but a narrow enough tie does not reach the bottom end around the spiral. Also tried lockwire and similar but will also try piano wire as it may be stiff enough. I also then thought I may be able to burn the interior of the spiral clean so heated it with direct flame from a MAPPGAS torch. I will now try an acetone soak and refit the GG and try it again. Next step is to get the oxy/acet gear and debraze it from the shaft, clean it out and rebraze it I think. These are simple machines and have no moving parts except pricker shaft mechanism so should not be this hard to fix. This lamp has served me for years in my hunting hut so I am not surprised it needs a little TLC. And it is fun to try and solve the mystery.
I use an old bicycle brake cable to clean the spiral of the vapouriser. It's not easy to get it started in the spiral but once there it can be worked around while rotating either the cable or vapouriser. A blockage in the spiral is a common cause of poor vourisation of the fuel.
Excellent suggestion. Kids bikes are now in jeopardy. much prefer this to de/re-brazing. Again thanks. A great boon of the Internet is the sharing of information and good ideas in community.
And..... The Bowden cable (bicycle brake cable inner) went in with a bit of effort and I eventually got it all the way to the lower end of the spiral tube of the GG but I could not get it to actually come out into the vertical tube so that I could see it. Measuring the cable off against the outside of the spiral I am thinking there is a strong blockage just where the lower end of the spiral GG tube joins the vertical tube. I tried spinning the Bowden cable to act as a bit of a drill but had no luck as the spring in the cable only lets it rotate so far then jams. There was a fair amount of crud came out of the spiral tube though which helps prove the hypothesis Looks like I am still going to have to separate the spiral tube to get at the blockage. All part of the adventure ....
Good work so far and good luck with the rest of things if you decide to un-braze .. be great to see some pictures of that Not unheard of for hard to see hairline cracks in vapourisers also, I believe? Best regards pb
Have you tried "heat and quench" ? The thermal shock causes heavy carbon build up to fracture making it easier to remove.
>>> The Bowden cable (bicycle brake cable inner) went in with a bit of effort and I eventually got it all the way to the lower end of the spiral tube of the GG but I could not get it to actually come out into the vertical tube so that I could see it. >>> That might not be a problem, since it may be caused by the brazing of the loop inside the generator. I usually block the straight way by a fitting screw or a piece of a tube, and blow through the generator so that the air will find its way through the coil only (if not blocked). That also blows out the loosened carbon if everything went well, so it won't block the jet later on.
