Hello All, I recently added this Optimus 1550 to my collection, the lever style preheater really sealed the deal for me. Is it safe to assume that the lead seals for this lamp should be the same as a Pmax or clone, or at least close enough that they would work? I really like the looks of this preheater. The operation is simple enough but how does the thing actually work? From my uninitiated eye it appears to be a flat plate on the inside with no sign of the semi-microscopic holes I'm used to on the Pmax. It operates pretty good but as there was a bit of buildup in the tank and it sputtered about a bit so it'll need a deep cleaning. I've yet to pull it from the tank and cannot find any actual pictures or drawings of what I'll find inside.
There is a hole at the very centre of that flat area you mention. Or atleast it should be. It might be totally blocked, and since it's so tiny, any obstruction might make it look all solid. The cleaning needle provided for this quicklighter is 0.19 mm, so the hole is around 0.20 mm. That's not so small, and generally you can see it if you look closely. I'll attach a drawing below that might help. If you remove the piece called "P" in it, you shall definitely see the hole if you hold it up against the light. The function is such, as when you turn the lever counter clockwise, the tapered end of the burner head is un-seated from the rotating piece ("P" in the drawing) and the orifice in it is opened. This allows the pressurised fuel and air exit through it where it's atomized so you can light it as a small torch. The two positions marked "T" in the burner head is just to point out where you might need further pricking if it wasn't enough to just prick the centre orifice. What this "T" marks is actually the two points where two small channels exits respectively; One for the fuel, taken from the bottom of the tank via the long, thin tube. The other is where the air comes out. This is taken from the very top of the tank, so also pressurised. You can also see that there's an o-ring at the burner head to keep the rotating piece "P" sealed against it. Perhaps it sounds complicated, but it all comes clear once you start to fiddle with it. I wager that all you have to do is to prick firstly the centre hole, and if that doesn't help, just unscrew the rotating piece and prick the two small holes in the burner head below. 0.19, or slightly smaller, will as said do the job. (The original one looks like a stove pricker, but those are generally much larger.) You can use a regular, loose lantern pricker if nothing better is available. Not just the same as for this lantern. That one is too large. You'll need a needle for a smaller lantern. 300CP, or perhaps even a 200CP. If not even this helps, you might need a better clean of the lower parts. There are e.g. a fine mesh at the bottom of the fuel pickup tube, and sometimes also at the higher point where the air channel starts (you will see it inside the threaded part close to where the fuel pickup tube is soldered to the burner base.)
Hello Christer, Thank you for the pictures and explanation. Mine is very dirty indeed but like any other new toy I just couldn't help but try it out. The lower part of the setup is very familiar and it's a straightforward design, the o-ring is a novel way to seal the handle.
Excellent description. My 1550 preheater has a leak when the lantern is pressurised and working. Your diagram seems to indicate that the nut holding the preheater on the tank should unscrew. I can move it at all! Is there a seal other than the O ring? When I tried to light the lamp using the preheater I got a fine stream of fuel which made a hole in the mantle. I didn't immediately notice the hole and escaping gas distorted and marked the new Scott glass! When opening the preheater should it just be a mist of fuel? The lamp lights easily on methylated spirits.
This sounds like there is something wrong with the preheater. It should give an atomised spray of fuel/air mixture which gives a blow torch effect. This shouldn't be strong enough to damage the mantle. I can see now from the drawing that the Optimus preheater has a straight thread, so would screw in using a lead washer as a seal. They should screw out. Maybe you should take a picture of it. Sometimes there is something that a picture reveals that is difficult to explain in words.
It's not leaking from the seal to the tank. Does something unscrew in order to replace the rubber O ring?
From the "Classicstoves" site: "That part is different than part that they use in current kerosene lantern preheaters(f.ex. Petromax & Optimus 1551). Same preheater is used also Heinze/Geniol military stove. In that 155 preheater flow of fuel is stopped by turning the nipple/jet. On those current Petromax(, Optimus 1551) and Heinze/Geniol military stoves flow of fuel is stopped by turning rubber pip into the front of the nipple/jet.". This implies that there should be a pip inside the housing?
Crossed posts. The preheater seals using the cone at the top of the lower fitting. This mates with a corresponding section inside the upper part. It is a brass to brass seal.
Prise the O ring over the top of the fitting and down over the threads into the groove! Got it! Now...where do I get a suitable O ring for this lamp... This lamp fettling is addictive! Thanks for all your help.
Can anyone provide the thickness of the o-ring & the internal diameter please? I'm looking to see if I have one for Seamanjive.
@Seamanjive I wouldn't mind betting that the O ring is still serviceable. How hard are you pushing the lever to close the rapid pre-heater ? I have an Optimus 1200 which has the same pre-heater as your 1550, I've had it in bits, cleaned it and polished it to try and get two perfectly mating surfaces which will make a positive seal but unless I use some force when I move the lever to the 'closed' position, it will leak. The hole in the centre is for fuel - which you say provides a strong stream of kero so is obviously clear - the air hole is on the side of the conical piece, to give you a clue as to where you should be looking, here is an image of a 250cp cleaning needle in the air hole. Ignore the black spot, it is a trick of the light ! Henry.
@Seamanjive Apologies, I've made a mistake. It's a long time since I took that image and my memory failed me. . WRONG ! In the image I posted, the hole with the cleaning needle in is indeed meant for fuel, the 'black spot' is in fact the hole for air. For a cleaning needle, look here: www.base-camp.co.uk/Petromax/Petromax Spares Price List. you need this item: 180 Cleaning needle, pre heater £ 0.90 Henry.
Thx for the update. I gave it another going over this morning...I just cant see the air hole. I might rub a bit of wire wool over it and see if it appears! I also had another go at undoing the whole assembly from the tank. Used proper fit ring spanner but cant shift it. The effort required damaged the mantle. This is a great lamp but its challenging me! I'll order the pricker and some mantles....
Decided to give it one more go. Success ! Put a box spanner over the nut and gave it a sharp tap. Pretty much wrecked the mantle but it had a hole in it anyway. This was enough to break the seal and I easily extracted the preheater assembly. Now I can see how it functions ! Cleaned out both holes with an .008 guitar string (I'd just restrung one of my Telecasters !)...perfect fit. Light tap on the filter gauze at the bottom of the fuel pickup tube to clear out some crud. Used another bit of guitar string (a wound D string since you ask) to clear some green crusty stuff under the cone and poke out the hole again. Rinsed it all out with some meths, tightened it back into the tank and reassembled the rest of the parts. Pressurised the tank. No leak ! Applied a flame to the tube and opened up the control. Stuttered a bit and then its away ! Closed it down and repeated a few times to clear out any gunk. Its working like a bought one! Easy to start the mantle...which is a bit ragged ! Thanks to all who chipped in. . .amazing forum this !
Well done there @Seamanjive you have the tenacity of a good fettler. It’s so satisfying to overcome the challenges that our lamps throw at us as we bring them back to life. Cheers Pete
Resurrecting an old thread, to thank everybody who contributed. I've a Optimus pre-heater that doesn't seal correctly and needs work on. It is the first time I have worked on one of these. A quick search, and the answer is here. What a great resource.
I’m having A similar issue here, with my Optimus 1350/350CP. It’s just blowing (or sucking, not sure) air. No petrol. I have cleaned all the parts of the pre- heater, except the small hole for petrol. Even the cleaning needle was too thick. I’ve ordered the picker tool, so hopefully it will do the trick. I’m a piano player, not a guitarist, and piano strings won’t work.
