Fettling a Optimus 80

[johneliot]

Before I decided to do this write up, I searched to see if it's been done on this site. I didn't find anything so I'll go ahead and post. It's long and picture heavy. I've done about 8 or 9 of these little guys, mostly 123's, but they're all the same. I got this stove because it came with the Optimus cook set. It's similar to a Sigg, just a little smaller. Everything was $45 shipped, so it was a good deal. The case has been burned. Probably why is was cheap.
First, take the jet off. I have a jar I put carb cleaner in. Toss in the jet;

I use an oil wrench and a 12 mm brakeline wrench to get the vaporizer/stem off. The oil wrench will keep the fount from turning while you use the 12mm wrench. The rag keeps the wrench from scratching the brass.


Here's the valve with it's wick. You can see the wire that helps to insert the wick into the stem.


The bottom of the wick which is in the tank soaking up fuel usually looks fine. It's the part that's in the top of the stem that get burnt and crusty and won't let the fuel "wick" to the top of the stem. You'll never see it until you pull out the wick. This is one reason for a weak flame.

Here's the stem without the wick, packing nut and valve stem.


This is the time to pick out all the old graphite packing. Various dental picks work great. When it's all out, the nut, valve stem and vaporizer all go into the jar of carb cleaner to soak.
Now for a new wick. The strands of wicks are just twisted onto the wire the last couple of times. Use small pliers to untwist and remove.

Here's the new 100% cotton strings from a mop head I bought. I got enough forever!

I unwind a couple of strings until I have 5 of them.

What happens most of the time is when you go to put the strands back into the wire, one of the ends break when you go to twist it together. Now you have to make another one. I use this:

I have a small punch I use that is the same circumference as the old one and I just twist. I make it longer than the old one and then cut it to size.


Open the end a couple of twists and then lay the mop strands, and twist it closed and the wick is done. I measure from the folded end to the tail and cut it at 4 inches.


The next step is to take all the parts out of the jar of carb cleaner and make sure all the crud is out. Pipe cleaners work good for this.

You should be able to plug one end of the openings and blow through the other two. If not there is still a blockage. I found out why this particular stove did not burn well. When I plugged the valve hole I could not blow from the bottom of the stem to the top. More soaking, shooting carb cleaner and compressed air finally got it open. I've never had this much blockage before.

Take the wick and insert it back into the stem. I found that "screwing" it in works great. Put it all the way until you only see the little hoop.

Next comes the graphite packing for the valve stem. This is what I use. I got it at McMaster/Carr for under $20 shipped. This will last forever too!

I cut it in half and wrap it tightly around the stem.


Put it into the opening and screw the nut back on. If the packing is too much the nut won't screw on. If that happens I'll cut another piece only this time a little shorter or a little narrower. When you can't get the nut on, the graphite won't be compacted so it's easy to get out and try again with the new piece.

Stem done.

Stuff the wick into the fount. Again, dental tools help here or a little flat head screwdriver. Anything that can help stuff the wick will work.
Just so I don't have to worry about it, I use a little of this Hi-Temp thread sealant from Permatex. Sorry for the fuzzy picture.

You counted the rotations and the clocking when you unscrewed the stem, right?

Light that little sucker up!

[hikerduane]

Nice tutorial. Emphasis on 100% cotton for replacement wick.
Duane

[dday]

Great write up John and it will help a lot of folks here. I've also done a few, but never took the time to take photos and document like you did here. Gotta love those little brassies!

[rescout]

Very nice. I've got one of these; if I need to take it apart I'll have this file. Thanks.

[Deanofid]

Well done on the write-up John, along with plenty of pics to show us the work. This will be
a handy reference for us guys who like these little stoves. Interesting and informative.

Just for guys who may not find that kind of graphite ribbon locally, Mike at OCP has it in
handy small rolls, too. Enough to do a number of valves.

John, if you'd like we can put this in the tech archives so it will be easier to find. Give it a
week or more here so guys can ask questions or make comments, and then if you want it
archived, send me a PM.

Thanks for the repair tips!

[Chucker]

Great tutorial. My Svea 123R is a reliable little stove.

[Gasman64]

Very well done, John, thanks for all the helpful pictures! You have educated me well. I have a 123, and this information will come in handy some day.

[johneliot]

Ken,
You are right. There are all levels to get these stoves going. I have gotten some from people who have taken care of them and all I needed to do was fill and burn. Some all I did was replace the wick and clean the jet. It will depend on how well the stove works. If I pull the stem and soak it in carb cleaner, I'll always replace the packing. Fettling the stove in the way the pictures show is something I'll always do when I get a new stove, whether it runs well or not. It usually takes me an afternoon and when it's done I never worry about a stove being ready for another 50+ years of service.
I always replace the cap gasket too. I have only had one stove get a little flame out of the cap. I opened it up and replace the pip inside and that cured the problem. I got this wrench from Bernie Dawg to remove the penta screw. I tried modifying a torx bit but it just chews up the screw. Just like the tool for removing check valves on Coleman lanterns, the right tool makes the job so much easier.

[johneliot]

I use this:

It's some cord I got from McMasters/Carr. It's Viton, 5mm wide. I use a sharp razor blade to cut. I have not been able to get the pips with the shoulder for the caps that are used with the pump. I think at one time Bernie Dawg or the Fettlebox made a cup that replaced that shouldered pip. I have not been able to get any.

[johneliot]

I use this spare bracket I have from my 69 VW. The hole is the right size for the cord. I put through the length I need and using a sharp razor, slice right along the bracket. It makes a clean cut. So far, the ones I have replaced seem to do the job.

[Chucker]

johneliot wrote: I use this:

It's some cord I got from McMasters/Carr. It's Viton, 5mm wide. I use a sharp razor blade to cut. I have not been able to get the pips with the shoulder for the caps that are used with the pump. I think at one time Bernie Dawg or the Fettlebox made a cup that replaced that shouldered pip. I have not been able to get any.

Tis the same type of Viton I'm using for all my PIPs now, maybe #65 hardness? I use a plier's style leather punch to get the PIP. It gives me a shoulder on the PIP and I like the broader surface.