Optimus 111T burner fault - A mystery solved!

Hi, I have an Op.111T which had similar syptoms to those described in a recent CCS Post and illustrated with photos:

https://classiccampstoves.com/threa...-shield-cobra-arctic-fit-a-111t-burner.38341/


1. The flame pattern is not symmetrical around the silent burner and the more powerful side shows a very fuel-rich yellow flame pattern.

2. I tried all sorts of remedies to solve the problem.

3. Fresh clean fuel made no difference.

4. I examined and cleaned the burner caps. They then looked fine so I re-fitted them. Didn’t help.

5. I cleaned the jet, tried new jet, applied copper slip to jet threads, etc. No improvememt in flame pattern and the over-rich flame remained in the same quadrant to the burner despite a new jet being used.

5. I then checked that the burner spigot and vaporisation chamber was undistorted and that the jet looked central under the spigot. I did see some minor damage on the top lip of the spigot tube...likely caused by localised melting during an under-burn incident, but the inner burner cap still fitted easily.

6. After each of the above potential “cures” I ran the stove.....with no success. I still had the very distorted flame pattern at all power levels, but particularly at full throttle..

7. Next I swapped burner caps with those from another Op.111T which I knew ran well. Again no luck! The burner caps I had removed worked well on the donor stove, so the burner caps were innocent!

8. I was stuck, I had tried everything and my sanity was at risk. So I fitted a spare roarer burner to this Op.111T, took some photos of the stove and posted them in the Stove Reference Gallery of CCS.

https://classiccampstoves.com/threads/optimus-111t-fitted-with-roarer-burner.31255/

9. More than two years later I was answering a question on CCS posed by a member whose multi-tool regulator spindle did not line up with the burner spindle of his Op.111T stove. I asked him to check the dimensions of the silent burner he was using, and dug out my now “Spare” Op.111 burner to take photos and make measurements:

https://classiccampstoves.com/threads/optimus-hiker-111t-multitool-handle.38153/#post-400090

10. After doing this work, I decided to revisit the problem. I refitted the silent burner to my Op.111T stove to see if the problem had gone away.....it hadn’t!

11. I decided to re-visit the burner cap issue. I set out two sets of burner caps and decided to carry out a hot-swap from one set to the other as I ran the stove. Run Stove - Shut stove off - Exchange Caps carefully using tongs - Re-start stove. If done quickly the burner head stays hot and re-lighting is no problem.

12. I carried out this procedure a few times but the non-symmetrical burn pattern persisted with both sets of burner caps and other combinations of inner and outer cap. Madness beckoned....

13. Trying once again, I happened to look down at the hot burner head just after I had removed both inner and outer burner caps. I saw a dark stain between the central spigot and the encircling vaporisation chamber. It was growing and produced a whiff of fuel vapour. This was on a shut-down but very hot burner! I HAD FOUND MY LEAK!

14. The underburn incident which I diagnosed as having happened before i acquired this stove had obviously done more damage than just partial melting of the top edge of the central spigot of the silent burner. It had opened up a small leak at the point when the spigot passes through the doughnut-shaped vaporisation chamber.

15. It seems likely that this small leak only opened up at operating temperature as I had tested the regulated burer under pressure, but cold!

16. I took the damaged burner off the stove and after thorough cleaning and preparation, silver-brazed the whole joint between vaporisation chamber and central spigot. It was not easy.

17. The repaired silent burner was thorougly cleaned of flux residues etc. then re-fitted to its parent stove. It worked as Mr. Optimus intended. I took some photos of the re-united pair and added them to the existing post on CCS.

Best Regards,
Kerophile.

 

Here are the images that monkeyboy posted in the above thread:

 

@kerophile

Excellent detective work on a very cryptic problem! Well done.

Cheers

Tony

 

Great example of a logical step-by-step process in investigating a fettling problem.

 

Mystery solved kero.

I had a near new silent 207 burner on an Optimus 535 that did the same thing(but not as bad as the one shown) and it had me bluffed as to what the problem was for quiet some time before I finally worked out the problem.

The burner was fully serviced to new condition again and checked for leaks, new seals fitted at the spirit dish but it still presented a distorted flame partially rich on one side even after trying to correct the problem using the much the same procedures as you did.

It burned perfectly blue on start up but after running awhile and getting much hotter it started to show the slightly rich flame always in the same position. No under burn though.

I played a small pencil blow torch on the affected side when the burner was running and discovered the leak when the fine blow torch flame turned from blue to yellow in the area.
It had a very fine leak that seemed to open up only when the burner was very hot.

It turned out that the vapor tube had not been brazed properly(but looked perfect) at the join under the vapor chamber of the burner.

Nearly drove me mad but I learnt from that experience so I now know what to look for if it ever happens again.
John

 

Hi @threedots I wish that you had told us of your experience at the time. It might have made my job a lot easier!
That joint between the vaporiser doughnut and riser/vapour tube is obviously a vulnerable point, be it for factory faults or damage in use/misuse.
Thanks for sharing your experience.
Best Regards,
Kerophile.

 

G,,day .
i like stories with a happy ending
this one has .
well done inspector .

kerry

 

Great work, thank you for sharing. My problem with cobra burners was dyed kero.
Duane

 

Hi @threedots. I'm interested in understanding more on this technique. Could you please elaborate on the torch flame turning blue to yellow and how a leak in the burner causes this? Jerry

 

Ain’t stoves (and certainly combined with CCS) a great hobby - Years of experience and we still learn something new!

 

Hello @kerophile and @Metropolitantrout .
About 2 months ago I mentioned on this topic
@Trouble lighting Monitor 2-pint silent (15?) Stove - about using a small pencil blowtorch to find small leaks at the joint where the burner riser to the burner spirit dish and the burner itself may be leaking. A useful way to find hard to find leaks on a hot burner and a trick I discovered some years ago.
I always try to get my stoves burning as blue as possible.

The butane fueled pencil blow torch can be adjusted so that the blue flame is small enough and not under too much pressure when being played where the leak may be.
Once the Kerosene vapor from the leak comes in contact with the butane flame, the flame turns from a pure blue colour to a yellowish colour therefore showing where the leak is.
Cheers, John

 

Hi @threedots and @Metropolitantrout . Same principle as using a Davy safety lamp to detect flammable and asphyxiating gases:

“ The lamp also provided a test for the presence of gases. If flammable gas mixtures were present, the flame of the Davy lamp burned higher with a blue tinge. Lamps were equipped with a metal gauge to measure the height of the flame. Miners could place the safety lamp close to the ground to detect gases, such as carbon dioxide, that are denser than air and so could collect in depressions in the mine; if the mine air was oxygen-poor (asphyxiant gas), the lamp flame would be extinguished (black damp or chokedamp). A methane-air flame is extinguished at about 17% oxygen content (which will still support life), so the lamp gave an early indication of an unhealthy atmosphere, allowing the miners to get out before they died of asphyxiation.“

From Wikipedia.

Best Regards,
Kerophile.

 

@threedots
@kerophile

Well explained, brilliant! Thanks to you both, Jerry

 

My Primus #5 lights up exactly like that but 2 minutes running and the red flame disappears.

 

Hello @Garth .
It could be possible that your burner may be coked up inside but not enough to stop the fuel from getting to a hot enough temperature to fully vaporise the fuel, as the burner gets hotter during use.
It could be near the point where it will coke up a little more and not vaporise the fuel sufficiently enough so that it will continuously burn poorly.

And/or your jet may be wearing(enlarging) so that it burns slightly rich to begin with until the burner gets hot enough to vaporise the fuel properly.

In both cases(an enlarged jet or coked up burner) your burner may burn poorly once you pump more pressure into your fuel tank so that your burner can't cope with the extra fuel flow as the heat needed to vaporise the fuel is inefficient.

Ps...I tend to write novels when trying to convey some of my ideas so excuse me if the instructions I give tend to be long winded.
John

 

This was like reading a great detective novel. A fun read.
Well done.

 

Thanks Kerophile and three dots. I appreciate those of you with high skill levels sharing your expertise. I know there are plenty of growing pains with our internet life right now, but here at CCS I think we experience the internet at its finest; people sharing their knowledge and experiences.

 

Good Morning, Kerophile, and All,

Excellent bit of detective work, George!! So far (knock wood!), I've not had any problems with my 111T burners, nor any of my Cobra burners. But, after reading of your fetting saga on this 111T burner, I'm going to file this superb information in a place where I can access it, should any such future problems arise! Thanks, very much, for keeping at it, when "everything had been covered", and thus finally sussing it out! WELL DONE, my friend!! Take care, and God Bless!

Every Good Wish,
Doc

 

took your advice Doc and did the same. saved it for handy reference

 

wow, now i know where the leak is on my stove. i don’t have the silver brazing equipment but my grandson does. i might see about offering this repair job to him.

the tube is expanded enough that i can not remove the inner burner without squeezing it some.as soon as i get the inner cap off i’ll inspect for a leak..

buzz