Hi all, I have an original Optimus 8r which I inherited and it is practically in as new condition and had only been used for a couple of fishing trips and at the time not used for over twenty years ( I am sure I posted about it on here a few years ago but I cannot find the thread so maybe I didn't ? ) When I got it, seeing it had been stored for so long, I followed the excellent tutorial on here and gave it a thorough service including replacing the wick and putting a new rubber seal in the fuel cap. I have used it probably half a dozen times over the past seven years ( guessing here ) with no problems. Recently I took it away for a weekend camp and after about running for ten minutes a flame just like an old gas cooker pilot flame ignited out of the brass fuel tank screw on cap. Is this normal i.e. a safety feature or is there a problem ? I duly turned it off but it was a beast to try and snuff the fuel cap flame.
There are two possible scenarios here- If the stove overheated, that would be the normal. The safety release valve in the tank cap (SRV) vents excess pressure, and as it is a flammable vapour, it ignites and burns. Overheating occurs with too large a cooking vessel used for too long on the stove- this doesn't sound like the case here as you were only using it for 10 minutes. There is a possibility the rubber seal inside the SRV has hardened with age- this happens regardless of how much the stove has been used. Oxone in the atmosphere, etc. This affects the ability to make a proper seal, and the SRV will release at lower pressures than standard. The SRV seal can be replaced, a search will show up various threads on the subject. The SRV is similar to that used on the Svea 123R, so search for that too.
That is the safety feature: a pressure release valve (STV) built into the cap. It sounds like you need to service it. There are plenty of posts here about that process, but a photo of your stove and with a clear indication of where the flame was coming from would be useful. Edit: crossed (again) with @Blackdog Edit #2: SRV service is shown in here (different stove; same SRV): Svea 123 Disassembly Cheers Tony
Petrol/white gas/ naphtha etc stoves are self pressurising through thermal feedback, rather than pumped. The fuel is also more volatile than paraffin/kerosene. The centre of the fuel filler cap contains a safety release valve (SRV) to prevent over pressurising of the fuel tank. This has similar workings to the NRV, i.e it contains a rubber pip with a calibrated spring behind it, although it is less easy to access it. So your "pilot type light" sounds to me like the rubber pip needs replacing as it is leaking a little. If the tank had overpressurised and activated the SRV, you could expect a jet of petrol vapour under some pressure. I just did a quick search in the search box (top right) for SRV service and it returned two pages for that reference. You will need to check the design of the valve to work out what tool you might need - all my 8Rs and equivalent need a penta key (a five sided allen key) to service it, you also need to make note of the number of turns of the key in order to load the spring to somewhere close to factory settings as this is a definite safety item. A Viton replacement pip would be recommended.
Many thanks for the quick replies they are very much appreciated . I did a search but turned up no results but probably inputted the wrong terms I think Blackdog has probably nailed the problem but will take all the advice onboard many thanks. Ps I will try and get a photo/s uploaded later.
Everyone did, I just got there first! Well done for searching first- many people don't bother. It was clear from your post that you didn't know the abbreviation 'SRV' commonly used here- without that knowledge, information is much harder to find for beginners and we all need to be mindful of that!
Does Optimus currently sell parts, e.g. the brass caps? As you may know, the 123R is still in production. The cap is the same, at least physically. Open cap surgery and replacing parts within is not always within everyone’s skill level or capabilities. A new cap sure would be a lot easier!
Does Ford sell parts for the 56 Ford? Sort of along the same lines. After market reproduction. New Old Stock. Learn to fix it. Pay to have it fixed.
Depends on what you value your time at, pip replacement is a pain in the you know what. First, care needs to be taken not to bugger the oddball screw. Special tool required, or near enough. There’s no way to know what the pressure will release at with the new part installed, unless one takes the additional step of actual measurement. Not a show stopper for inveterate tinkerers, but. If we could buy a whole new cap for 12 bucks or something like that, I’m confident many if not most would think this preferable in a lot of ways?
Fettler, great suggestion. I never thought of that! Just looked at Base Camp's site. They list : 2044 Tank lid, T88 stove £14.95. The T88 is a Hiker plus and when I checked the fitment of the lid from my Hiker (don't know the model number but black tin, green tank, Nova burner), on one of my 8R's, yes, it fitted and looks just the same as my original 8R cap with the penta fitting. I am sure Mike would be able to advise on compatibility. Might be a more expensive option but if someone wants a working stove and not a fireball and doesn't have the confidence to play with this safety critical item, then that could be the way to go. If I had a 56 Ford, there are service parts that I would still expect to buy new if I wanted to keep it running, although I have never had a Ford, but have had 50's Austins aplenty.
Ha! Touche’. But I’m simply pointing out, while you or I may see this kind of thing as routine or fun or a labor of love, other folks don’t want to make a deep dive into stove arcana & fiddly bits, they just want to get Gramps stove going again with the least hassle. I am a card carrying member of the DIY club, but sometimes, I my favorite tool in the toolbox is my Special Checkbook Tool.
If you're going to do that, I would toss the defective caps you're replacing into a jar or something. I don't know if Base Camp's lids are still being made, but it's only a matter of time until they aren't. ....Arch
Might be a neat little cottage industry for someone who could turn them out. I’d buy one. The Svea 123 and the 8R have a loyal following, there are some “aftermarket” parts offered by hobbyist vendors on eBay, as far away as South Korea. Maybe he is making fuel caps too, have to look. A “discharged” safety release valve is kind of a show stopper, albeit one of the only parts that will ordinarily fail. The other being the cap gasket.
“Easily” you say, though not for most people. That’s the only reason for suggesting this option, it’s always nice to have alternatives. If anything, buy one to have a spare for future use or repairs.
