I’ve recently been working on a nice little 1939 (AD) Primus No 4. As received it was missing both burner caps but otherwise seemed in good condition. Closer inspection revealed that it had been dropped or had something dropped on it as there was a bend in two burner tubes, the burner spigot had been pushed into the tank and it was leaning at an angle. I straightened the burner and spigot but the tank retains the character giving depression. After flushing, replacing the seals and pricking I fitted borrowed burner caps and lit it. It burned strongly with reasonably blue flames but something was amiss as there was flame coming through some of the holes in the bottom of the burner top ring and it would frequently ‘blow out’, become a roarer and turn the outer cap red (unless I was quick releasing the pressure). Nevertheless it was enough of a success to warrant further restoration as I thought de-coking the burner would cure the burning problem. My usual procedure followed of soaking small parts in vinegar, painting a vinegar/flour mix on the tank, electrolysis and a re-spray for the windscreen, heat/quench for the burner then polish all the brass. Unfortunately the brass fount didn’t respond very well as there were green blotches all over it which, when removed, revealed pitting. My guess is something in the past seventy one years has leached the copper from the brass. I polished out the worst of it but had to draw the line with what you see before you here: Despite being slightly disappointed with the finish I was expecting it to be cured of the burning problem so lit it and again it burned well: Alas, it still wasn’t right and replacing the jet nipple and fitting a different outer cap (with a more flared bottom) were in vain. Indeed post fettle the escaping flame could even be worse than before as are the ‘blow outs’ – I can’t even get it to burn long enough for the tea-test: So, I have a nice little stove that’s as polished as I feel I want it to be and doesn’t burn properly. Not my most successful fettle and all I can think of now is to keep trying different inner/outer caps (those used came from a 55 so are they too big?) and flush the tank again. Any thoughts?
I have had problems with underburn and here is what i did: https://classiccampstoves.com/threads/14750
Hi John, It looks as though you have the wrong burner caps! The No.4 burner uses smaller caps then the No.5 stove. https://classiccampstoves.com/posts/52575 Base Camp had Con-branded No.4 outer caps for a bargain £2 or so. Unfortunately the inner caps are very hard to find. Hope this helps. Best Regards, Kerophile.
Hi John I very much like the way your stove looks! It has more character than a flawless polish. Nice! I'm guessing that a proper set of (smaller) Primus #4 caps will set you straight. The outers in Primus metal are available from Base-Camp. Part #P4204. They have the brass versions, too, though the Primus metal burn better in my opinion. The Cons kerophile mentions are nice, too, and a bargain. Inners are extinct, though I'm thinking you may have a PT on that subject soon. Cheers, Gary
Thanks guys, a combination of a call to BaseCamp on Monday and a generous PM I received and the problem of my ill-burning stove is solved. It must be the size of burner caps that's the issue rather than a mis-aligned jet as the 'underburn' (as I now know to call it) is fairly even and not just lop-sided. Good tip on straightening a jet though. Shame about the pitting but at least it's obviously old with character and not fresh from the factory. It's also such a pretty little stove I'm inclined to forgive it. Cheers, John
Hello John, I totally agree with Mr.Dawg on the looks of your Primus No.4 stove. Not only make the imperfections for a true vintage look, they also set it apart from those Primi that are polished to original specs - making them look like eh...the rest! Mind, there is nothing wrong with a clean and shiny classic stove, but personally I 'go' for character, and yours has plenty! Great fettle and good to read a solution might be underway; thank you for sharing! Regards, Mike
Primus-metal cap for my No 4 just ordered from Base Camp - their last one and I've got it - hooray But they're busy so won't send it out until Wednesday next week - boo Cheers, John
I should rename this thread to: "Primus No 4 - fettled and now WITHOUT problems" Thanks to Gary (BernieDawg) for supplying an excellent ‘Made in the USA’ inner cap, Base Camp for the correct size outer cap and all you helpful people for telling me I was using the wrong caps in the first place and my lovely little No. 4 is back in service and working well. Here’s the proof: No underburn now: The Burner Caps: Compared to No. 5 caps: I have bigger stoves and I have smaller stoves but the proportions of this one just seem so 'right'. So, a very, very nice little stove is brought back from the brink. Thanks to all. :smile: :smile: Cheers, John
Hi, John, WELL done, Sir!! I'm so glad you kept at it, and sussed out the problems, as your stove is definitely special and a "keeper"!! I also agree with Dawg in his comments about the way your great old stove looks. It's earned it's appearance, and that patina just makes it all the more special!!! Again, congrats on your hard work and efforts, and a tip of the hat to all those that offered help and bits, along the way! Well done, Mates! Take care, and God Bless! Every Good Wish, Doc
Hi John, I am so glad that you have your No.4 stove working well. These burners are really special IMO and look great. Well done, Best Regards, Kerophile.
