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Optimus No:8R First Steps: Filler Cap & Wick

Discussion in 'Fettlers Master Class' started by Ian, Oct 28, 2007.

  1. Ian

    Ian United Kingdom Subscriber

    Jul 26, 2004
    West Riding of Yorkshire
    Optimus No:8R First Steps: Filler Cap & Wick by Ian Marson

    You have your Optimus 8R in front of you, so what now?

    Open the case and the contents should look something like this. The filler cap may be different, there may be a control knob instead of a key, the flame spreader may be slightly different, but all in all it should look something like this.

    Remove the working parts from the case. This is only a spring fit on the flap so it should be easy enough. Remove the heat deflector too; another spring fit. Also disconnect the key & chain from the case. It will be easier to attach the chain to the pot rest than attach the key to the chain.

    Remove the filler cap and empty any residual fuel into a suitable receptacle. It is quite awkward to get all the fuel out as the filler tube extends into the tank to prevent overfilling, but a good shaking about will get most of it out. Put the tank etc. to one side and turn your attention to the filler cap. Look at the seal. It will doubtless have a circular indentation caused by the rim of the filler tube. Prod the seal with a small screwdriver. If you can feel it give slightly under the screw driver it is probably ok but prise it out all the same. If the seal is hard and/or cracks and breaks when you try to prise it out, it will have to be replaced.

    If you can flex the seal like this, the chances are it is ok. It is good practice to replace the cap seals on stoves new to you as a matter of course. If you don't have a spare you can obtain one from Base Camp in UK or A&H in US. Alternatively if you have some suitable material, 1.5mm nitrile rubber jointing is the ideal, you can punch a replacement out yourself using suitably sized punches or even short pieces of tube as punches. If you don't have nitrile to hand, the soft plastic of a washing-up liquid bottle will make a passable stopgap.

    I didn't have any of this but as my seal was soft and flexible I settled for refitting it upside-down to the way it was.

    Screw the filler cap back onto the tank and then ensure the valve is fully shut; turn it clockwise until it stops. If it won't turn clockwise it is already (most likely) shut. Remove the burner basket/cup by unscrewing it from the body of the valve:

    Open the valve fully by turning the key as far anticlockwise as it will go, and then look across the top of the nipple. You should be able to see the cleaning needle sticking out of the nipple like this:

    Close the valve and you should see the needle withdraw into the nipple.

    Now remove the burner assembly from the tank. The correct size spanner (wrench) is far and away the best thing here and what I would call an open ring but in US is called a line wrench is better than a bog standard open-ended spanner.

    I didn't have either to hand so used a small adjustable and care. Incidentally, in the field, a small adjustable and a multi-tool will serve for almost all your fettling needs and many other jobs too.

    When you have unscrewed the burner assembly withdraw it and the wick from the tank with a gentle wiggling motion. When you can get hold of the wick with your pliers or finger and thumb do so and gently pull it out to avoid leaving bits of old wick in the tank. (These are not easy to remove). When the wick is out if it is still wet with fuel squeeze it with a rag or paper towel so it isn't dripping fuel all over the place. Now is a good time to rinse out the tank with clean fuel. If the tank contains grungy residues, and it may, something stronger such as carburettor cleaner or engine cleaner may be required. When you can rinse your tank with clean fuel and it comes out as clean as it went in, it will do.

    Going back to the burner assy. Separate the strands of wick close to where it enters the delivery tube. There should be a piece of wire sticking out. This one has a loop but often they don't and sometimes you can't find any wire at all.

    Grip the wire and wick with your pliers and, holding tank in one hand and pliers in the other, exert a steady pull with a little twisting motion so that the wick and wire withdraw from the delivery tube.


    Unravel the old wick and you should see that it is nipped in the end of the wire. This wick looks pretty good.

    I use strands of ordinary cotton domestic mop-head for stove wicks and find that they are just right. This one is 14" long but ⅔ of that would do.

    Unbend the nip in the end of the wire, remove what's left of the old wick then middle the new wick and nip the wire around it. If the wire isn't going to be long enough to protrude about ¼" from the delivery tube when pushed up it as far as it will go, you will need a new wire. Any thin stiff copper or brass wire will do. An opened out paper clip will do but non-ferrous is better. If you have enough length of wire to form a loop, or even just a small dog leg, do so as it makes the next bit easier.

    Hold the wire by the loop and twist it so that the wick spirals closely around the wire.

    Continue this until the wire is covered with the wick then grip the loop end of the wire and the wick with your pliers and insert the wick and wire into the delivery tube until it stops. If it is difficult to insert, the wick is too thick. Take it out, unravel it, un-nip the wire and reduce the thickness of the wicking. A mop strand is made up of three yarns, so take one out and try again. If the wick slides into the tube freely, it is too thin so take it out and add a yarn. You don't have to use mop strands - any suitable natural fibre will do. Twisted gauze bandage works well in my Russian 8R clone.

    When fitted your new wick should look like this:

    Now, set the burner assy. close to the tank so that the loose ends of the wick can be pushed into the tank, then moving the delivery tube closer to the tank, gently prod the wick into the tank with your screwdriver until the threaded portion of the delivery tube will screw into the tank.

    Screw the burner assy. into the tank. This is a tapered thread and hand tight should just about bring the axis of the valve spindle parallel to the axis of the tank. If it screws too far it will stand being loosened a touch. If needs be use a little thread tape or instant gasket so that the burner sits square. Avoid, at all costs, forcing the burner assy. round for nearly another full turn as this can permanently damage the threads.

    Refit the burner basket & heat deflector to your stove and the guts back into the case, then take your stove outside. Place the stove on a firm level surface and remove the filler cap. Fill your stove about two-thirds full, i.e. up to the bottom of the filler tube. It doesn't take much to fill an 8R so something that offers a degree of control is better than just sticking a funnel in and slopping it in. In UK Coleman Fuel or panel wipe are the ideal fuels and in US, Coleman fuel or white gas. Auto fuel should be avoided, although it will work for a time, as it contains additives which will clog up your stove.

    When you have filled your stove to the correct level, screw the filler cap on. Finger tight should suffice.
    You can prime your stove using its own fuel; Open the valve and warm the tank with your hands until fuel bubbles out of the nipple and into the priming cup. Alternatively, if you have the mini-pump and its associated cap you can use that but bear in mind that, on a full tank, you will only need a single pump stroke of half an inch at most to get the fuel moving. When the priming cup is full close the valve. If you wish to prime with spirit there are any number of droppers, squeezy-bottles, etc. to facilitate getting spirit into the cup but I find that gently dribbling spirit over the top of the burner until the cup is full works as well as anything. When your priming cup is full ensure the valve is shut then light the prime.

    When the priming flame is all but done open the valve a quarter turn anticlockwise and your stove should light satisfactorily.

    Put the coffee on.
    Last edited by a moderator: Jun 26, 2015
  2. colemanblues

    Jul 7, 2011
    Thank you for this info, It was most helpful in several ways.I received this link from a fellow CCS member trying to help me out. I am starting to fettle with a Optimus 99 mini. And was asking for advice.

    I just cannot get the idea in my head of building a fire in the cup, before lighting the stove.Yes,I am a newbie to the forum and these little jewels. Got hooked quick. Just been it to it about a mounth, and aquired several stoves already.

    You seem to be the goto Guy for parts. I saw you have some listed on the bay also. But i did not see what I an needing. I am in need of a rebuild kit for my 99 mini first. Also need kits for 2-8R's, and a 111B.If you can help wth these let me know, and we will work out getting you the $$.

    Thanks again for all of your advice on the forum, and helping us newbies.

    Best Regards, God Bless
  3. Spiritburner

    Spiritburner United Kingdom Admin Subscriber

    Jul 23, 2004
    N.E. England
    Don't thank me! :lol:

    This was written by Ian Marson for our old site & I just transferred it here.

    Thanks Ian! :clap:

    I only do the 'software' - washers & seals. For hardware I recommend Basecamp.
  4. colemanblues

    Jul 7, 2011
    Thank you for the info on Replacing wicks on these stoves. This Info was on an 8R, but has helped me with many stoves. I have just been fettlin with my stoves, I have never lite a stove yet. And I still cannot get it in my head to build a fire under the TRUE FLAME, to get that FLAME. But Thank You.

    I was givin Ross all the credit for your work, and I thought he was going to take the Credit, But he Manned up and told the truth. Joking with ya Ross.

    Thank you all, God Bless
  5. fuzzy

    Jul 14, 2011
    Thanks for this article, I recently acquired a 8R with the mini pump, the 8R was taking 2 bowls of meths to prime before it ran and when I tapped it little sparks shot out the burner. I've taken the wick and it is pretty much burnt sold at wire end.
    Thanks again
  6. collarandhames

    Jun 16, 2014
    This has been the best thread I've ever come across and answered so many questions about my optimus 99. Clearly I probably need to address the wick issue. I have fiddled with this thing a lot, and get it running, but always sort of , and never full on flame. I will replace the wick, and hope that this solves many of the issues. Question: with white gas camp stoves, can you replace leaky o-rings with regular off the shelf hardware store 0-rings? I have so many leaky fuel filler caps on so many pieces of equipment, and recently purchased a o ring assortment kit. I await a response before I rebuild my treasures. Thanks for this website, and thanks for being there. I am in peterborough ontario canada.
  7. geeves

    geeves New Zealand Subscriber

    Sep 29, 2009
    Wellington New Zealand
    hardware o rings might be made of anything so I would want to know what they are.
    Viton is best if you can get it but good nitrile rubber is just about as good although some stuff sold as nitrile is not as good as it needs to be
  8. ruck up

    Dec 24, 2014
    :content: Many thanks for your skill & expertise. I now have the confidence to fettle up my new to me 8R.
  9. Templogin

    Templogin United Kingdom Subscriber

    Jul 28, 2015
    Shetland, UK
    This is really useful. Thanks a lot for taking the time to produce this.

  10. Pstm13

    Pstm13 United States Subscriber

    Oct 27, 2015
    Upper Snake River Valley
    This helped me a lot. I just picked up a 8R the other day and really like it.
  11. Tony Press

    Tony Press Australia Subscriber

    Jun 8, 2013
    I'm "bumping" this thread because someone recently said they were about to fettle an Optimus 8R or a 99 (I can't find that post now), and they needed advice.

    This thread is a very good start for both stoves.



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