Poseidon Xstream tuning?

[Kupu]

I have picked up several used Poseidon second stages, including an Xstream. The Poseidon world is new to me.

Opening up the Xstream, it was very clean inside. No signs of salt water use and no visible build up of any type, so I did not run the parts thru the ultrasonic cleaner. Perhaps a mistake, but everything looked so clean it seemed a waste of time. The servo valve needle was bent, so replaced that along with the valve insert and all orings. From there, reassembled and adjusted the valve tube to just above the point of free flow. First stage IP right around 123.

On a dive, I found that trying to sip air was not as smooth as I like. It cracks easily and provides a little bit of air fine. From there, inhalation effort comes in steps up as I demand more air rather than a linear pattern. So rather than being to take a long smooth breath, I have to make small adjustments on how hard I inhale during a complete breath.

I was expecting the Poseidon the feel a bit different, but as it breathes right now I prefer the more natural breathing pattern of a "standard" second stage. The Deep6 second used as alternate was more comfortable to breath from when comparing side by side during the dive. I feel like the Xstream should perform better, but perhaps I am just experiencing the love it or hate it type breathing that has been mentioned by some.

Is the valve tube the only adjustment point assuming first stage IP is correct? Any parts I should consider replacing aside from the servo valve and valve insert?

I also rebuilt a metal Cyklon second. Ran the parts thru ultrasonic, installed new rubber plate and exhalation diaphragm, then adjusted the orifice and set low pressure valve about 1/8 turn short of fully open. First stage IP around 168. Test dive revealed a very smooth breathing regulator that is a keeper for sure. No additional adjustments needed, it is perfect.

 

[tbone1004]

that breathing experience is how servo assisted regulators work, don't try to sip on it, it's not designed for breathing like that. If you ask for air, it will most definitely give it to you. It's a new breathing pattern and you'll love it or hate it.

There is only one adjustment on those and it is screwed in or out. There is a field service guide out there on how to tune it using the strategically molded notches on the regulator to get it to behave properly. Not sure how you tuned it, but it's possible the cracking effort is too high. There are no other parts to replace because nothing else moves.

The Cyklons are quite nice and sexy when tuned properly!

 

[Kupu]

that breathing experience is how servo assisted regulators work, don't try to sip on it, it's not designed for breathing like that. If you ask for air, it will most definitely give it to you. It's a new breathing pattern and you'll love it or hate it.

Thanks for the input. I will give the Xstream a few more dives, but may be set in my ways regarding breathing style preference. I wanted to verify I was not missing something that can affect performance before walking away. I have used the Omega and Hollis servo assisted regulators, the design is a bit different and I have found their breathing pattern to be very smooth thru the full range of inhalation speed.

There is only one adjustment on those and it is screwed in or out. There is a field service guide out there on how to tune it using the strategically molded notches on the regulator to get it to behave properly. Not sure how you tuned it, but it's possible the cracking effort is too high. There are no other parts to replace because nothing else moves.

The Xstream service manual was used for reference during the rebuild. I think cracking effort is as low as it goes, turning the valve tube any further out results in free flow. I did not notice the reference to tuning notches or see them on the regulator. Something for me to look into.

The Cyklons are quite nice and sexy when tuned properly!

I love the look and performance. It has potential to become one of my favorites, I am looking forward to more dives with it.

 

[tbone1004]

@Kupu if you decide against it and want to trade it for a cyklon, let me know!

 

[Kupu]

@Kupu if you decide against it and want to trade it for a cyklon, let me know!

I will keep that in mind, and was considering finding another cyklon to pair up and use as alternate.

I used a Seapro Fail Safe alternate on my first test dive with the cyklon, as someone had said it was intended to be used at higher than normal IP. It took the 168 IP with no issues, but it is not a long term solution since it has a purge button that protrudes a little from the cover. A few times during the dive I brushed my arm across the top of the Seapro causing it to purge a little.
I first tried pairing a SP109 with the cyklon, but could not tune it to avoid free flow at high IP.

 

[Bigbella]

I was expecting the Poseidon the feel a bit different, but as it breathes right now I prefer the more natural breathing pattern of a "standard" second stage. The Deep6 second used as alternate was more comfortable to breath from when comparing side by side during the dive. I feel like the Xstream should perform better, but perhaps I am just experiencing the love it or hate it type breathing that has been mentioned by some.

I'd second that the cracking effort may be a bit too high, on the Xstream. Poseidon allows for a wider range of adjustment on that model. My Xstreams all have effortless breathing -- and they're little more but pared-down Jetstreams . . .

 

[Kupu]

I'd second that the cracking effort is a it too high, on the Xstream. Poseidon allows for a wider range of adjustment on that model. My Xstreams have effortless breathing . . .

Thanks for the comment. I wish I had an Xstream known to be perfectly tuned to compare with the one I have on hand.

I am unable to tune to a lower cracking effort using the valve tube, just a 1/16 turn or less from where it is now results in light free flow. I had considered the purge diaphragm as possible point that could affect ability to properly tune, if it was misshaped or otherwise faulty, but it appears to be in good shape. Not sure what else can be done.

If nothing changes, I might not rule out sending the Xstream to a tech that knows them well just see if they are able to achieve better results. For now I will continue to play around with it and see if anything else is revealed that could help. Its not that it breathes badly but just not to my liking.

 

[Bigbella]

I was unsure of what you were using, in terms of manuals, when futzing with the regs; and you're fairly certain of the IP; that it is stable?

Here are a couple of the most recent versions -- one, a field repair guide for the Xstream, that may be handy . .

 

[tbone1004]

@Kupu where in NC are you?

 

[Kupu]

I was unsure of what you were using, in terms of manuals, when futzing with the regs; and you're fairly certain of the IP; that it is stable?

Here are a couple of the most recent versions -- one, a field repair guide for the Xstream, that may be handy . .

The service manual you attached is what was used for reference during the rebuild. I did not have the field repair instructions, thanks for providing that and now I understand the reference to adjustment marks.

Before taking the Xstream for test dive, I had reached a point where the tuning seemed good after the rebuild. Perhaps slightly stiff breathing while taking a light sip of air, but nice and smooth otherwise. I not at all sure about this, but maybe the breathing became a little bit rougher near the end of the test dive. Or perhaps I was getting used to the regulator and thus more sensitive to little variations.

This morning, I took some breaths from the regulator and confirmed it was not to my liking and started this thread. I have been playing around with tuning today and right now it seems slightly improved. I am fairly certain the locking screw was tight enough to stop the valve tube from moving during the dive, I had to loosen it to make adjustments today. But it makes me wonder if somehow the tuning slipped just a little during the test dive.

I pulled a Scubapro MK16 out of storage to use and adjusted IP to 123 on a tank full half for the rebuild and test dive. I just had another look and now see 114 on full tank and 121 on low tank. I have plenty of options for other first stages, just need to sort thru and find something else to try. Right now the Xstream seems to breath the same on full and low tank, but think I can do better to get the IP where it should be.