Optimus 8R: Is this slow?

Thanks for this forum. Wonderful place.

I have an old Optimus 8R I bought in about 1970, used only once or twice. I recently pulled it out because I will have a use for it.

I'm not sure it's burning as hot as it could. Using coleman camp fuel. It takes about 15 minutes to bring a pint of cold tap water to a boil in a cover mess kit.

Any advice? Thanks. Tim

 

Hi Tim, Welcome to CCS.

Your Optimus 8R is really slow; you should be looking at sub-5 mins to boil a pint of water. If you reckon the flame is small the first thing I would check is the filler cap gasket,as these stoves are self-pressurising and rely on the cap being totally gas-tight.

The gasket must be be flexible and resilient. Give the gasket a prod with a small screwdiver, not hard enough to cut the gasket, just enough to see if it indents and then springs back.

If the gasket is hard, replace it with a new one made from Nitrile rubber, as it has to be fuel-resistant.

Let us know how you get on. If the gasket is OK we need to check other things.

Best Regards,
Kerophile

 

Welcome Tim

I agree with Kerophile, it is more than likely the gasket/seal

You also can't fill the tank over 3/4 full. There needs to be air behind fuel to pressurize correctly.

Here is a pic of a 8r running to give you a idea of the flame.



Cheers,
Jeff

 

Thanks. I'll check the gasket. And my flame is nowhere near that.

Tim

 

Do the dunk test, in hot water. Bubbles = leak.
Use a Nitrile or Viton rubber.(fuel resistant)

 

Thanks again to all. I checked more advice on this site and noted that the tank had left a firm imprint on the gasket after about 30 years in storage (with the tank lid turned tight). So I turned the gasket over, and lit it up.

Yes! Big difference! Big flame! Pint of cold tap water to a boil in just about exactly four minutes.

Will order new tank gasket.

Tim

 

Well done!

 

Bravo! A very clever solution.

I recently tried to buy a replacement gasket for my Primus 71, but I was told that I should just replace the whole cap because the pressure relief valve may be blown.

QUESTION: What do you all think? I've heard of so many people on this site just replacing the gasket. Is it really necessary to buy a whole new cap? It's probably not overly expensive to replace, but I sort of like that I have all the original parts still on the stove. Is this something specific to the Primus 71 since it's relief valve is built into the cap?

 

Some American members make their own seals, perhaps one could send you a couple if you ask?

 

Good idea.

Do you think I have to worry about the pressure relief valve? It seems to me that if the stove pressurizes and runs well that the relief valve must be OK, yes? Or is that a false assumption?