Precise 8r Clone questions....

Dear All,

I recently acquired a Precise 'Phoenix' Asian copy of the Optimus 8r stove. It has the brown painted tin box, etc. The stove does run, but the flame is weak. I replaced the cap seal and it maintains pressure somewhat better, but, still, the flame tends to be rather weak even after robust priming. I did resort, finally, to using an optimus pump with a two way cap to increase the tank pressure, and that immediately helped, but I really would like to figure out how to make this stove run properly without having to add pressure artificially, as it were. Also, the burner 'bell' does not thread unto this stove.... there are no threads, and the burner just sits on top precariously and falls off easily. Is this normal?
Cheers,
Karl
Weimar, California

 

Greetings, welcome. The SRV pip in the cap may not be sealing. You can check for any leaks by removing the tank and burner from the case, loosening the cap, place in the freezer for 15 minutes, tighten cap and place the whole thing in hot water.
The bell may be off of another stove.
Duane

 

Burner bell should have threads and screw on, so it stays securely in place. You may be able to squeeze the base of bell you have with pliers to get it to stay in place. Careful not to shrink the hole to small and damage the threads on soft brass valve body. Since stove runs with added pressure jet should be not plugged. Sounds like you know how your stove should run, loud and hot. Hopefully it will get there soon. Daryl windy SoCal

 

Do bear in mind these types of stoves ( I was using an Optimus 99 last night) take a while to heat up and build enough pressure to get to full power.

Surprised the Optimus cap threaded on.

 

Thanks for the tip. I just tried a new cap from my Svea stove-- new seal and, actually, a brand new cap... the pressure remained too low. I will try the freeze technique. I was surprised that the stove had not threads for the burner bell-- no threads at all! Weird. I will try the pliers idea-- that just might work. I ran the stove for a full tank, and it never got enough pressure. I have found other stove users who mention that the 8r design does not work as well as the Svea design-- and one guy even said that he had to use an optimus pump to get his 8r up to full pressure. I am curious to know if other people have found the 8r design to be less than ideal. In the 'Complete Walker', Colin Fletcher gives a sound thumbs down for the 8r design (he sent a couple back and, finally, just kept using his Svea). I have seen photos on this forum of 8r stoves (and clones) that really look like they are burning robustly, but I wonder if there are just stoves that never run hot from new?

At any rate, thanks all for the help. I will try the suggestions and get back to you all.

 

The 8r -99 style stove does not put out as many BTU as the Svea 123. But I used mine last night, melted snow, and had hot chocolate and MacnCheese. Just not in a big hurry.
Are you trying stove inside? If you are outside, in the cold, any breeze will zap it's strength. Same if you are sitting it on a cold surface.

You are aware that if you open valve much at all you will start closing off jet woith the cleaning needle? Gotta find the sweet spot.

I have a Stansport ,which is a 99 Taiwan clone (just an 8r with an aluminum case) and it is a bit more powerful than my Optimus 99.

 

The dunk test, mentioned above, will reveal any leaks.
Please report back where bubbles come out.

 

Good to know that the 'Precise' stoves can be powerful-- I have one of their Phoebus clones and it is as good as the Austrian Phoebus. I am a long-time user of stoves (20 years as a professional Mountain Guide), but I am not very experienced with fixing them, so I appreciate the expertise on this site. I just started digging out my old stoves and trying to get them going again. And thanks to this site, I found out about how to purchase new seals, etc. I will report back.

 

So, I did the freeze test. The cap was leaking (steady bubble stream) even with the new seal. I noticed that the brass edge of the filler tube was rough, so I filed it smooth and polished it. On the second test there were no bubbles coming out from the bottom of the cap, but there were some occasional bubbles coming out of the safety release valve on the top of the cap, but not very many (occasional here and there). I primed and lit the stove but, still, the same feeble output. I am guessing that when running, the safety release valve must be leaking quite a bit more than when I freeze tested it. With lots of priming (alcohol) it will get up to a barely satisfactory running level, but within 10 minutes or so, it starts to shoot yellow flames, as liquid gas spurts out in a pulsing fashion. This must be due to the cap leak and resulting loss of pressure. I guess I need to repair the release valve, etc.

 

If there’s no way for the burner bell to screw on, I’m wondering if there’s enough thermal feedback to pressurize the tank properly.

….Arch

 

I had not thought of that; the burner bell is on there tight (I crimped the edge a bit). Also, I tried a new cap that I bought from Taiwan (ebay) that I use on my Svea stove, and it also lost pressure-- makes me wonder if the srv valve is not that bad on the original cap, and that the loss of pressure/poor performance is due to something else mysterious to me.

 

Arch might be right about the thermal feedback.
Can you heat the tank .. slightly ... with a small torch? If you get a good flame, after the tank gets warmer, then you know that it is the thermal feedback.

 

Try putting soap bubbles on cap when running. couple T's of water with few drops dish soap then whip it up with fork and dab on. May also try placing pan of water on stove to get some reflective heat to fount. Your getting close to removing burner from fount to check wick I think. Use heat & brake line wrench, that connection can be tight.

 

Thanks everybody-- I am learning a lot about these, apparently, simple stoves. I have checked everything now: wick is perfect, no bubble leaks when frozen; no bubble leaks when tank is pressurized; no bubble leaks from SRV. Anything I have missed? I am inclined to think that the problem must be thermal conductivity due to the fact that the bell burner is not threaded unto the stove. The burner bell is attached, but the attachment point is slim (a slight crimp that allows it to not wobble off at the slightest movement). A previous owner must have stripped the threads and then removed the threaded part, etc. That is all I can figure. This stove just won't maintain pressure. Even when I heat the tank, it roars to life, but within a few minutes, it gets feeble again and then it starts to squirt out liquid fuel. It seems like there must be a leak somewhere, but no leak can I find. So, I infer that it must be a thermal failure-- the bell burner is very hot, but, perhaps, the heat is not getting to the tank. But, at the same time, the tank is hot to the touch (not burning hot, but hot all the same). What am I missing here? The physics are beyond me. Thermal 'feedback' depends upon a certain amount of brass to brass connection-- I must be missing the critical surface contact for that to happen.

 

May have missed this but you are using Coleman or Crown white gas correct? Seems like you have ran stove long enough so you don't have over filled condition. Maybe attack the top end and remove jet, cleaning needle and stem to check for crud. I may be wrong but I believe they can run without the cleaning needle? Might try switching jets if you have a similar stove. I know in lanterns incorrect jet size will cause problem. Just brain storming here as you can see. Daryl

 

I have removed the needle and cleaned, etc. I am using Crown White Gas. I did run it long enough to get to low fuel level. I will try another jet, however. I thought of that, but figured it was not imperative. I will also run it without the cleaning needle (I usually remove those anyway from my Phoebus and Svea stoves). Thanks.

 

Well rats! Maybe a different jet will change things. Maybe in a day or two someone will have a fix for you. My hat is off to you for all the work you have put in. Take care Daryl

 

You'll need the thermal feedback to keep the tank pressurized and fuel vaporized. Something in the fuel line from tank to burner or a screen in there plugged up?
Duane

 

Arch has got a good thought, I recall that last year somebody went thru this, and the lack of good thermal feedback was the culprit.
If you can heat tank and this thing roars, it's not a jet issue, or a needle issue, and a pressure loss you will see (I use a spray bottle with soapy water.)

 

Try cramming some aluminum foil into the space where the threads should be. (Maybe wrap the area below the jet with a couple layers of foil, and then force the burner bell into place?)

This won’t be a permanent fix but if the performance is noticeably better, it would support the thermal feedback idea.

….Arch

edit: Also, a photo of this unthreaded connection would be helpful.