Just received an old 1928 Primus No.4 (S13 stamp) in sorry state. The tank riser joint, filler mount joint and air release screw mount joint all leaked. The outer cap had a 2mm hole in it and there was no inner cap. Leaks were identified with soapy water and re-soldered. The outer cap hole was filled with a small piece of 2mm diam. copper electrical wire riveted in place and filed flush, then sealed with Silflo 30 braze. However, the lack of inner cap was the main problem as I don't have one, and can't seem to be able to buy one. A makeshift inner cap was made from a plumbing fitting with the outside rounded and domed, then polished to aid gas flow, (I remember polishing engine ports). The result is fine, and will do until I acquire a genuine replacement pair of caps.
Hi @Twoberth https://classiccampstoves.com/threads/fettling-a-primus-4-inner-cap.8768/#post-88194 And from Base Camp: P4196 Outer cap in Brass for burner 4126. Stove 4, £5.75 Best Regards, Kerophile.
@Twoberth I must have a weak spot for those No 4 stoves and the small silent burners, have got a couple and played quite a bit with them. I am a few hours away from my parts boxes right now, but I just might have an inner for that little burner, pm me if you feel like it. All the best, e
@Toad of the Cape The Primus No.4, as shown here, takes a 4125 or 4126 silent burner. It might also take a 4127 roarer burner. Tony
@Twoberth @Toad of the Cape I too have made inner caps for some of my No.4's, and some Juwels which use similar, from copper pipe blanking caps(here). Works perfectly well as also shown by Kerophile's BD link above. I wonder if the heavier brass coupling version requires more pre-heating? Ian
@igh371 Hi, the coupling cap didn't require any more preheating. Its a normal size spirit cup which I filled to just above the washer line and the burner lit first time after the meths had burned out. However I will try the blanking caps just for fun until I get pukka replacements.
Made my inner cap out of copper pipe end stops, drilled and shortened. Working very well. No extended pre heating time, I use a pilot tube fixed to the burner and it also works very well.
