In 1999 I bought an Optimus 8R by mail order from a well known London retailer. I'd wanted one since 1975! Apart from a few test burns, it hasn't been used.

When I got it I was struck by how 'roughly hewn' the brass work was. It looked like it had been made by some worker the worse for aquavit. The tank itself looks like Optimus has played a staff football match with it and in any case it is made up of two quite irregularly shaped parts: the seam (with less overlap than I've seen in any pictures of an 8R/99/199) falls obliquely across the tank, rather than at a tidy right angle to the tank's axis. The angle of the seam stands out all the more because the smaller 'half' of the tank varies in depth by a good eighth of an inch from shallowest to deepest part. This variation in depth is more than is needed to true the overall proportions of the tank, given the oblique cut across the main part, so it just adds to the distortion. Then there's the jet and spindle housing, which joins the fuel tube at a good bit less than 90 degrees. Don't they use jigs when they're brazing these components together?

At the time I did wonder whether or not to send it back. But then I thought I liked the 'character' of it: after all, the hand made look is all part of the charm of these things. Were I interested in Mars probe technology I would buy a Whisperlite, Nova, Himalaya or some such gadget - perish the thought.

Now however, my 8R is teething. Firstly the flame lost its guts, so I removed the jet to check for blockage, only to discover that the cleaning needle was bent back on itself. Then when I opened the tank to drain it, I noticed that the wick was floating free in the tank, nowhere near the fuel tube! It wasn't like this when I bought it so I assume that either it wasn't pushed fully home from the outset, and has since come adrift, or that maybe it has been forced out of the tube with pressure from boiling fuel in the spindle housing, when I've inadvertently blocked the jet by trying to clear it with a bent needle!

That's not all: I have some spares and checked the existing jet, once removed, with a new needle. The needle passes through the jet less easily than it passes through a brand new jet, so to avoid a repetition of the same problem with the new needle I'll be using the new jet as well. But the jet remover on the regulating key won't fit over the new jet unless I either file the jet the down a bit, or open up the hole on the key! It's a good job Optimus never made rifles. This is probably a timely reminder that it's best not to use the regulating key as a spanner anyway as it's likely to cut into the soft brass. I normally use a very small shifting-spanner for this sort of job which gives better purchase.

To get the wick back in I'm going to have to remove the fuel tube from the tank. I assume that the wick should go in with the copper wire twist pointing back towards the tank, and I also assume that the head of the wick should be pushed as far into the tube as it will comfortably go (and ideally all the way?). The copper wire twist on the wick (which itself looks as good as new, and so it should) is only five-eighths of an inch long - the twist in the 8R schematic suggests that perhaps it should be longer. Maybe this was another casualty of aquavit! Does anyone know what sealing compound I should use when I remarry the fuel tube with the tank? Optimus have used some kind of sealant during manufacture. I'm familiar with the usual gas (I mean the domestic gas supply here, not petrol or gasoline) jointing compounds used in the UK but suspect that hot heptane-naphtha mix under pressure may require something different. Something which might be used in a petrol or diesel engine, perhaps?

This is not the end of the story. I bought a Midipump to use with the stove, and the cap valve which comes with this won't even retain the pressure of a single stroke of the pump: with this cap on the tank, therefore, I doubt that the tank is holding any pressure created by warming when the stove is in use.

To paraphrase one of the Collectors, I couldn't see me kicking this stove all the way to Scotland: I don't think I'd get it past the garden gate. However as it took me 24 years to get my 8R I'll keep trying.

I'd be grateful for any advice about relocating the wick and suitable sealants for the tube/tank join, and I'll bear in mind the 'five tooth rule' when reassembling the spindle and needle.

By the way, an 8R tank plus spindle housing and spirit cup, stripped of all its remaining parts, makes a very good desk ornament (I have it in front of me) and, owing to it being very tactile, is an excellent stress-buster.

Many thanks

Patrick

Since 1975? That would be 24 years.

Allow me to chip in my couple of red cents.
It appears that your 8R was made by a drunken apprentice on his first try, 5 minutes before 5PM, on Friday. Here in the States, we used to have cars from Detroit roll off the assembly line that way, until Japanese cars began to outsell American cars. But I digress.

8R's cleaning needle can be synchronized by skipping 4 teeth. I use 4 teeth skipping, all my 8Rs work perfectly that way. Maybe 5 is good, too.

Your 8R seems to have the wick that should belong to Svea 123. You are right: the wick stem must be slightly longer than the fuel tube, when inserted all the way. I make my own wick with cotton twine, and every one of them perform admirably. I do unravel the twine, in order to increase the absorption area. I would suggest that you try making your own, before dropping a few pounds for a new wick.

The sealing compound I use is alcohol based. It dries soft, but hardens when fired up. When cools, it hardneds again. Then high heat from the burner seems to soften up a little. Anyway, there may be better ones, such as teflon tape the plumbers use, but I used alcohol based one, thinking the white gas would not dissolve it.

There is a maintenance kit for 8R (for Svea 123R, 111, and Nova, as well), and you might find its contents useful. If your jet is giving you a trouble, the kit may have the one with the correct orifice. The old 123s have tighter orifice than 123R, as I found out.

As the far as the cap is concerned, there are only two things that need to be checked. The washer-shaped seal in the cap, and the small button shaped rubber seal hidden in the little tube that houses the check valve assembly.

Sometimes the rubber hardens up over time, and loses its ability to form the airlock. Press it with a pointed instrument to check for its serviceability. You can make it yourself, if you can get a piece of rubber sheet that is impervious to pertoleum product.

The check valve--the button seal--that is located within the short tube, is pushed up by a tiny spring. It may not be giving enough force to keep the hole closed. Then again, it could have hardened over time. Remove the tube by twisting counterclockwise. Inside, you will find a tiny spring that holds a tiny rubber seal. Stretch the spring just a little (I DO mean JUST a little; it is very easy to over-do it) and reassemble the cap and pump it up. Repeat until you are satisfied with its tension to keep the air in. If you over stretch it, you risk deforming the spring. Or, pump will not overcome the resistance of the check valve and will not pump air into the fuel tank.

Good luck, and look forward to hearing from you good news.

There is no sealant at the connection between the tank and burner. It is a metal to metal joint. The diameter of the mating surfaces tapers and this forms a gas and liquid proof joint. A sealant could make the burner difficult to remove if this was needed later.

Thanks for your reply. Since posting my query I have unshipped the fuel tube and it looks unlikely that I'd get the wick all the way as far as the spindle housing even if the wire twist were long enough to facilitate this. Other than for the length of the thread and nut (which corresponds roughly to the five-eighths of an inch length of the copper twist), which has a bore sufficient to accommodate the wick, the tube itself narrows by about one-sixteenth of an inch. This is barely greater than the diameter of the loop binding the wick together, never mind the girth of the wick itself.

Of course, it could be that I've been supplied with the wick for a 123R (but surely they have separate production lines?) if it is the case that the proper 8R wick is not as stout as the one I have.

As for the button seal on the fuel cap for use with the Midipump, I can't really examine that until I get hold of the right type of key (being a five sided Allen key). I don't really want to chew up the head by using pliers on it.

Apologies for griping about the quality of my 8R. I'm looking forward to buying a Manaslu 121 very soon so maybe I'll wax lyrical about that.

Patrick

Thanks for your response, after reading which I unscrewed the fuel tube from the tank.

I'm sorry if I sound impertinent, but on my stove a sealant has been used in manufacture, even if this is not the usual practice. It has been smeared into the thread and around the shoulder surface. Not only that, the sealant appears to be a product widely available in the UK from DIY stores and plumbers' suppliers. It looks like 'Boss Super Green' (or similar), a non-setting, fibre impregnated pipe jointing compound with PTFE. I have a tub of this and I note that it is supposed to be safe 'on water, compressed air and oil to 21 bar and steam to 14 bar' and hot water up to 7 bar at 200 Centigrade. Given that a stove like the 8R probably operates with a tank pressure somewhere below 2 bar (even with a pump) and that the tank never gets too hot to touch (therefore staying well below 200 degrees), the use of this compound is plausible. Even if the temperature where the fuel pipe joins the tank exceeds the average temperature of the tank, it still looks like this compound could have been used, as the variables probably work out to lie within its performance envelope. But I'm no engineer so who am I to say - it's not the sort of gamble it's wise to take!

Patrick

I too waited over 20 years before getting around to buying the stove I always wanted. In the interim I used an altogether different classic stove which served me very well over the years, but that's another story.
The long term object of my desire was and is an Optimus 111 and I successfully bid for one on eBay at the second attempt. It arrived in lightly used condition and apart from fitting a new pump cup needed nothing doing to get it working as God & Optimus intended. It is, or rather, until yesterday was, most pleasing to the eye (it's a bit singed now but thats another different story which may be found elsewhere on this page) and has functioned in a first-rate manner for the few months which I have owned and regularly run it. I cannot fault it.
So, it would seem, stoves are in the same barrel as any manner of other manufactured apples - there's a bad 'un in there somewhere. B2M is right, you are a patient man indeed. Given your stove problems I would have had it winging its way back to the well-known retailer PDQ with a heavy dose of "what-for-and-what-are-you-going-to-do-about-it?" hot on its heels.

Could it be...a mutated 8R?

Well, the fuel tube that connects to the fuel tank should be a straight pipe, inside and outside. At the deep end of the pipe you should be able to see the small hole that meets the tip of the spindle. You may even be able to see its tip, as you turn.

But if you are correct in your assessment, the tube seems to be tapering inside. If so, I would not know what to do with a tapering fuel tube. Maybe, if you know a competent machinist, he could rebore it to the proper caliber.

In the past, I have laid both wicks of 8R and 123 together, and I noted that the wire length is about twice as long on 8R. A small portion, say, 1/4 inch, protrudes from the end of the pipe. That way, you can grasp it, when you want to remove it.

Here, I am assuming that we are talking about the cap that receives the pump, not the one that comes with the stove. This cap has a short tube on the side that goes into the fuel tank. If you do not mind, just use the channel lock or visegrip to loosen the tube. Proceed with caution. Do not put too much force. You need just enough force to grip the tube and not slip and damage the brass. It easily turns, and you can finger-loosen it.

Inside, you will find the black button seal stuck in the tiny spring. If the arrangement is not this way, it is the sign that someone had been there before you.

Inspect, and make sure the seal is soft. It may have a circular indentation from the relief hole. It becomes an issue, only if the rubber is hardened. You might want to stretch the spring, if you suspect it is compressed too much over the years.

But at this point, your main problem is with the wick. Compounded by the tapering inner wall of the fuel tube, you may not be able to insert the wick far enough. If the wick is not inserted all the way to the end of the tube, the stove may develop surging and/or weak flame. Then again, whoever inserted the short wick may have chosen to do so, since the proper-length wick would not enter.

It may help to make your own wick, and see if that will aleviate the problem, if you do not have an access to a new one immediately. Find a length of wire of similar gauge, and fashion is around about 8 strands of cotton twine, according to the model of the original wick. You can determine how many strands will give you the snug fit. Too thick, fuel will have trouble reaching the jet; too thin, air will escape along with fuel. You can observe this at the jet, as you pump up the fuel tank, with the fuel level below the connection point. The fuel comes out bubbling.

Hope you get some results.

Mutant? You're beginning to make me wonder!

The easiest way for me to describe the fuel tube is like this: the outer diameter of the tube beyond the nut is 7mm; it is bored out to slightly more than 6mm to a depth of 14mm (effectively the depth of the thread plus the nut) beyond which and up to the spindle housing it is bored out to 5mm. I know this because I've inserted drill bits (tail end first) of these diameters into the tube (sorry to have gone metric, but most of my drill bits are metric).

Does this sound right? It would tie in with the short length of the copper wire twist on the wick, enabling the wick to be inserted all 14mm of the 6mm bored section with a little of the twist protruding for handling.

Either this is how it was intended (so that fuel would be transported into the 5mm section of the tube where it can form a pool for vaporisation) or otherwise the whole tube is meant to be bored to 6mm, and the gent or lady on the Optimus production line has trimmed the copper wick twist at 5/8" (16mm) because that's all they could get in! The wick certainly fits very snugly in so far as it will go - I can't see there being any chance of any air getting into the 5mm section from the tank when there's sufficient fuel in the tank. If anything I would say it more likely that vaporised fuel would be forced back into the tank from fuel boiling in the fuel tube and spindle housing. Indeed this is how I think the wick may have become dislodged.

I will add that when the stove was working, it appeared to be working properly, with a hearty flame, especially when used with the pump. Boiling times for 1 litre of water corresponded with Optimus' own performance specs for use both with and without the pump.

As for the Midipump cap, yes I am referring to the cap with the extended tube which comes with the pump. I can picture the button seal arrangement inside the tube, held shut by the spring. Only it isn't held shut by the spring, as it rattles about! So either the seal has hardened and shrunk as you say, or the spring has been compressed somehow. I think seal shrinkage is more likely, although if true I'm peeved as this shouldn't happen to a seal that's only 5 or 6 six years old and has spent most of its time on a shelf in my house!

You've given me plenty to work on.

Thanks again.