JetStream free flowing.... sort of

[jazzyj8]

I have a jetstream reg that was given to me by my father in-law. He only used it on a couple of dives and didn't like the way it breathed. I had it serviced just to be safe as it sat in my closet for a few years.

My question, when I am breathing through it everything is fine. As soon as I remove it from my mouth whether under water or not it goes into free flow mode and is getting harder to stop. My LDS readjusted it and says everything is fine.

Is this normal?

 

[Oceanus]

Constant free flow is not normal for any reg. It is a sign that the reg may need to be serviced or at minimum tuned. Sitting in the closet a few years may seem harmless, but actually it can be worse for soft parts which harden and or deteriorate with the lack of use.

Adjusting a reg is a bit of an art. The ideal tune has the reg just on the edge of free flow so that it is "easy to breath". IF the tech is too conservative the reg seems a little hard to draw gas from (how most octos are tuned). IF the tech as checked the reg and found everything to be in order then it seems they have just been a little too aggressive with the tuning and needs to adjust it to be a little more conservative.

Generally you can stop a mild free flow by covering/sealing the mouth piece with your hand (which creates back pressure).

 

[scubafanatic]

...I'm confused....it sounds like it WAS free-flowing, but that has now been fixed...thus, there's no more problem, is there ? You should be able to hook the reg to a tank, turn the tank on and see if it's really fixed.....assuming you didn't already do that before taking the reg home from the LDS. I own several Jetstreams, although I really don't dive them anymore and have them stored in my closet.....I've been diving Apeks/Atomic/Mares instead for the last few years. Jetstreams are still good regs and have been proven reliable...however, it's harder than average to find a good reg tech for them....they're a bit quirky to tune properly...and parts are more expensive than average and harder to obtain as well...over the years Poseidon has gone through a number of parts distributors in the US and parts availability has varied widely. In your case though, at least the reg is a 'freebie', so it's likely worth tolerating those Jetstream 'downsides'. On your original point, it's NOT supposed to free-flow....EXCEPT that it's common for them to free-flow once the tank pressure drops to about 300 psi, which is due to the 'wierd' design of the 2nd-stage and not something I'm going to go into here.

Karl

 

[kittyhawk]

The Poseidon Jetstream is one fine piece of engineering. It gets a reputation of being difficult to service becasue of the parts problem. The reality is that there is a little known secret to getting them right. The main parts that need changing are 'O' rings. and the silicon 'condom'. Under most conditons, the silicon part of the 2nd stage valve would last forever... as long as you don't lube the silicone components with silicon grease.. 'Krytox' seems to not attack silicone parts.. I'm cheap, I just use 'olive oil' to help things along, since I don't dive Nitrox. Canola if you are even cheaper. Or just use Johnson's baby shampoo... for silicone parts...

Anyway, the 'o' rings are metric, at least all the substitutes i have found to match are metric. NBR 90 seems to work best.

The biggest headache encountered is the servo valve. It's classed as non serviceable and need to be replaced and it is bloody expensive. However careful examination will reveal that it is indeed serviceable and the there is an 'o' ring in that little sucker. once you have very carefully disassemble the servo valve, you will find that it resembles a shraeder car valve. same principle.. depress the needle and pressurised air is released. The servo valve is easily serviced but often not becasue of the cost..

You can use an NBR 90 or NBR70 AS568 002 'o' ring. I find the NBR 90 works better for me. Lasts longer and gives a feather touch feeling. The 70 creates a softer seal and detunes the servo valve and does not last as long. I replace this 'o' ring every season.

o.k. The magic here is that the servo valve allows the silicone diaphram valve to dump a lot of air very quickly. By adjusting the length of the servo valve stem, the sensitivity can be varied significantly. The slider switch provides some compensation.

Those of you who found that you have free flowing problems is surely an indication of the servo valve 'o' ring not sealing well or is marginal or there is debris in the seat. If it freeflows stop playing with the servo valve. It is likley the rubber is non existent and you have metal to metal contact. If you continue playing with the valve, you will wear the valve seat.

Hope this demystifies the servo valve...

If you need NBR90 002 'o' ring PM me. or in fact any NBR 90/70 FKM 90/70. I've got it all. Thanks Vance! Your book was inspirational!!

I should have taken a series of photos to show how to service the servo valve. Next season or if one of you wants to post me an old valve and i'll do a strip and build article.

Regards
Kittyhawk.