Elementary question: How to remove a burner from Optimus 157?

My Primus #5 was like that and I had to use the pricker a lot to keep it running at all I was preparing myself for cleaning the burner.then I got one of those stove top ovens which I decided to run on the Primus, I'll see how hot this thing can get the oven I thought so pumped it up things got very warm indeed oven reading near 600 degrees and a Primus so hot I needed pliers to release the pressure knob a lot of strange sounds as carbon was ejected from the burner since that episode I've not had to use the pricker and have the perfect flame. Try running that burner hard, it may actually clean it out.

 

@Garth quite a good idea that. Many burners may not have had a good hot run for a long time.

Same argument with the 'old ladies car' that's always done the local shopping. It'll need a few hours thrash on the motorway to clean the crap out.

 

That's two votes. I ran it for about 5 minutes and nothing changed. But perhaps it was not long enough? In any case, it seems easy enough, with nothing to loose, so I will give this a try.

thank you!

 

I ran my #5 for a full tank before it started to come good 5 minutes wont even start to heat it the lomger it runs the more it will improve its probably only been used for kettle boiling in its life and is choked up

 

Will definitely try that!

Should I add some odorless mineral spirits to the tank? I read somewhere that this makes the burner run hot which is what I want, right?

 

I didnt but my stove top oven reflected a lot of heat downwards even a good part of the trivet glowed red im thinking a barbecue plate or large pot might do the same my #5 when I got it showed very little sign of use and really didn't put out a lot of heat probably only boiled the odd camp kettle I have actually used it a lot lately and it just keeps improving it does seem they enjoy extended hard use

 

Its getting a workout at the moment.

 

Makes me hungry

 

Was considering buying a coleman oven then this shiny one was offered for $10.00 and it works very well like it was designed for the primus

 

OK, it is definitely winter here (polar vortex and all), no sailing! So I can finally focus on my stove problem.

To my great joy I found (probably re-found) that I have two brand new burners in the parts box, among gazillion other things, both new and used. The previous owner must have been an even bigger hoarder than me. I gained access to the underside of the burner (4 screws, easy-peasy), put a wrench (I think it was 3/4") on the nut below it and turned. It came off without a hitch, as did the burner. I already declared victory internally. So I put on the new burner, with a flexible washer (I have several of that, too, probably asbestos) and tightened the nut as much as I thought was appropriate for brass threads. I then moved the whole apparatus into the cockpit, in case something would go wrong, and procured a fire extinguisher for good measure.

Feeling I was close to victory, I poured a good quantity of alcohol into the bowl under the burner and prepared to light it. But when I got out the matches -- wasn't there less alcohol than I thought I put in? And wasn't the alcohol level dropping as I watched? A quick peek at the underside confirmed it: the alcohol was leaking down. Now the threads were already as tight as I thought was prudent for brass so all I could do was to add a second washer (it turned out the old burner also had two fiber washers). Unfortunately this did not solve the problem, still leaking.

Closer inspection revealed a small difference between the left burner (which is the one I am working on) and the right one (that I did not touch): If you compare the two attached images which show the undersides of the two burners (excuse the grunge, this is a working piece of equipment and not a collector's item), you will see that the bracket under the left burner is straight (not under load) while the one on the right is ever so slightly curved. So, there needs to be some force on the washer that keeps the alcohol where it belongs. For some reason even with two washers (same number as under the old burner) the distance is still a little too long. Therefore there is no force on the bracket, therefore not onto the washers, leading to the leak. I measured the lengths of the threads, they seem to be within a millimeter of each other and may well be identical.

So, my first question: Should I try again, adding a third washer? Or even a forth?

Since it was not that easy, I decided to take the two burners home (not very comfortable to work on a boat at well-below freezing temperatures!). And since I have it here, I figured I might as well restore the old burner and either re-install it or keep it as a spare. The old and new burners on my bench are shown in the third picture. So I took off the jet and the packing nut of the regulator. I then turned the regulator all the way to the left until the internal threads disengaged (and the prick thing fell out, a bit to my surprise but I caught it) and tried to pull of the packing. Well, I pulled mightily, even put the burner into a vise and pulled on the wire that I had threaded through the hole in the stem but it did not budge.

Thus, my second question: How do I get the graphite packing out?

Finally, the last picture shows the situation after I took off the burner (even more grunge , I promise I will clean it up!). There is a conical aluminum washer on top of the kerosene tube which I did not take off. I see several of them in the parts box.

Third question: Am I supposed to replace this aluminum washer?

Thank you for your help!

 

Oh, one more thing:

After I got the jet off, I blew into the burner. I expected a lot of air resistance but there was really none. Is my assumption that the problems with the burner are due to accumulation of carbon in it correct? Is there some thinnish layer that prevents the kerosene to be heated up to temperature?

 

@OldMariner

I am not familiar with this stove, but my advice would be:

1. Re-assemble the stove the same way it was assembled previously, complete with the aluminium washer.

2. Don’t load it up with multiple washers. I would use some copper grease on the threads and nip it tight, but not overtighten or you will distort the fibre washer(s).

3. After taking the pricker rack out of the burner and unscrewing the control shaft, heat the control shaft tube with a propane torch and squirt a bit of oil where the graphite is; then pull and unscrew the control shaft.

4. The burner can be blocked by carbon. “Heat and quench” is a means of cleaning out the carbon; or heating and burning it out if you have a way of pumping air into the burner while heating the carbon enough for it to catch fire and continue to burn with a flow of air.

5. Heat and quench should be done carefully: heat the burner to dull red, then drop it into water; tap the burner on wood to shake out loose carbon. Repeat; repeat; etc. The careful part is not overheating spots on the burner. The burner can crack.

6. If your replacement burner is the same as the one from the stove I see no reason why it should not fit with all the original fittings.

I hope you get this thing going.

Cheers

Tony

 

Yes, Optimus advise replacement every time the burner’s removed and re-fitted. In fact I’ve managed to get away with a few re-uses but your photo indicates it’s overdue for replacement with quite pronounced annular grooving, which would make the joint prone to leak pressurised fuel.

Take a look at my dismantling of an Optimus 155 HERE

Photos showing what was then a copper conical washer in place on the fuel feed tube ...




... the same conical washer as it makes the seal in the burner inlet opening




... later issue conical washers are made of aluminium

 

Good eye! I did not even notice the ridges on the alu washer but the photo clearly shows them.

And thanks for confirming that the 'conical copper washers' can be in aluminum! I thought I was missing something.

The alu washer will be replaced

 

So, some progress, I just don't know how much. Let me explain.

First, I built a real redneck version of a de-coking station, literally with chicken wire and duct tape. The idea is to set the burner (after removing jet, pricker and regulator) on top of a vertically oriented 12" nipple of 1/2" black pipe. The burner is held in place by judicious application of chicken wire. The pipe nipple is clamped to a saw horse placed in my garage so I have some empty space around it in case something goes wrong (nothing did). To the bottom of the pipe nipple is duct-taped the hose from a bicycle pump. See the attached pictures. When I now look at the pictures I realize that the background is very busy (my cluttered garage!) so it may be a bit difficult to make out my contraption. I hope with the description it all makes sense.

How did it go? Pretty well, actually. I chose black pipe to reduce heat conduction and it worked great, the bottom of the pipe was completely cool. When I applied the propane torch, very quickly a nice yellow flame came out of the regulator hole. (I had meant to close this off with a 5/16" bolt which someone on this site had said was the right size but it is not. When I thought about it, I did not really see a reason why this hole should be closed, it is right next to the outlet (jet) anyways so I don't think it makes a difference whether is is open or closed.) I figure that was just some kero that was still in there. After a minute or two of heating the burner some greyish smoke came out. I continued to heat the burner, moving the flame around while pushing air through the burner with the bicycle pump, for probably 5 minutes or so.

I don't know if the metal got red-hot since it was still light but the wire I used to hold down the burner definitely got red hot. The burner metal also changed its color where the flame hit it. After it cooled, it looks very different, no more oily residue, it has a somewhat rough texture.

While I was doing this, always nervous I would end up melting the solder joints, I realized I never asked here how long I am supposed to heat the burner. How do I know that the inside is clean? Is there any way to find out before I mount it on the stove? Mind you, it is a bit of an expedition to test this on the stove since the stove is on the boat, actually in the boat. So I have to move the stove outside the cabin (not easy because if just fits through the companionway) and then do all the testing outside in the wind, at freezing temperatures. So it would be really nice if I could be somewhat confident that the operation worked.

So, any idea if my five minutes of heating and blowing did the trick?

Thanks

 

@OldMariner

If you now get your burner and tap it on a wooden block, does any carbon fall out the bottom?

Also get some pipe cleaners and run them through the tubing as far as you can.

If you’re not getting carbon flakes and dust you may have got there.

The final test is to put it back together and see if you get a good steam of air through the jet.

Cheers

Tony

 

Thank you! Nothing fell out, as far as I can tell. I don't have pipe cleaners but I could buy some. I definitely get a good stream of kerosene out of the jet (see next post) but I did not expect otherwise. As I mentioned earlier, there was virtually no resistance when I blew threw the burner with my mouth, before any cleaning. Does that mean the whole decoking was not needed?

Will report on the life testing in the next posting but would appreciate an answer to the question. Thank you!

 

OK, here is what happened today. I went to the boat and put the cleaned (??) burner on the stove, after replacing the conical alu washer. When I poured alcohol into the cup, it leaked. That was with two gaskets which it had before. I added a third, no leak. Good!

Then I pumped up some pressure. In response to Tony's post: I got a very nice stream of kero through the jet (was not surprised by that, see above). Then the moment of truth: Preheated and fired her up!

I missed to take a picture but it definitely was NOT a yellow flame. It did not start beautifully blue but that may have been because there was a leak at the regulator. I tightened it to the point that I could not turn the shaft anymore but there was still a flame. Looks like I damaged the graphite packing when I took it out (this took some effort, as reported above; application of oil as you (Tony) suggested helped but I still had to apply some force). The shaft was getting quite hot and I was afraid I might damage the plastic knob so I turned it off. Changing the packing is not a big deal, I have spares but I decided to do that at home, not on the boat (in below freezing conditions). And I was also eager to see if the brand-new burner would work, and to solve the mystery why it had not sealed previously.

So I put that on, also with 3 gaskets. Leaks! Bummer!! Added a fourth gasket, and that did it! No more drips, hooray! I did not even have to tighten the nut to what I considered the maximum for brass threads, a quite reasonable amount of force worked and it did not deform the washers too much. I fired'er up again, and both burners are working with a nice blue flame now, see pics. The replaced one is the left one, shown also by itself in the second picture.

The only concern I still have is that the range over which I can regulate the flame is a lot smaller with the new burner. When I turn the knob more than about 10 degrees in either direction the flame starts to go out. With the old one (both the replaced one and the 'right' burner shown in the picture that I did not replace) the range was more like 50 degrees, maybe more. And the flame seems to be weaker, it never reaches the power of what it used to be. You can actually see that in the pictures, there is a lot less 'blue flame' visible in the left burner. This is something I could live with but I wonder if there is something that could be done to bring the range to what it was before.

Any suggestions appreciated. I am definitely making progress, with your help!

 

@OldMariner
I’ve lost track of when you set the pricker rack in each burner - the so-called counting of clicks, but with a decoked burner (which sounds like it never needed decoking) obstruction of the jet - and I’m thinking a pricker needle set too high on the rack pinion of the control spindle - is the only rational explanation for the subdued performance in contrast to the other burner.