mk2 x-stream to pair with my cyklons

[Joris Vd]

Dear scubaboarders,

I recently purchased a second hand mk2 x-stream.
I've done some dives on the xstream and really dislike the second stage breathing compared to the cyklons. I quite often do very shallow dives and I felt especially in shallow dives it's not the most comfortable because it tends to 'flutter'. It wasn't impossible to dive, but certainly not the most comfortable.(not compared to for example a balanced adjustable paired with a legend or something similar or even my cyklons)

But because one of my old cyklon first stages is so beat up, I wondered if I figured I could pair the xstream with the cyklon second.
Now I know that the mk3 is the only x-stream poseidon endorses with the cyklon seconds.
My poseidon hoses do have these opv nibs on the end of them so in theory shouldn't a first without an opv work just as well? I also read about some issues in earlier x-streams with wear on the diaphragm by people who used to pair the x-streams with cyklons and cranked up the ip. Is this also the case for the mk-2 deeps?

I've gotten the cyklon tuning down to a tee and love them so much, I'm just not ready to accept the x-stream second stage into my life

 

[Caveeagle]

Shallow breathing was never a strong point for the Jetstreams, and probably not for the Xstreams either as they are very similar.

I am not sure how you think the integral hose-end opv will have any use for a cyklon second stage as they have totally different fittings.

you should not need an OPV for a cyklon second stage, as it’s a downstream design and will just free flow if the IP goes crazy. ****not the case for xstream or jetstream, which NEEED the opv ****

pm me if you want to sell your Xstream second stages, or trade for cyklons or parts.

 

[Bigbella]

Dear scubaboarders,

I recently purchased a second hand mk2 x-stream.
I've done some dives on the xstream and really dislike the second stage breathing compared to the cyklons. I quite often do very shallow dives and I felt especially in shallow dives it's not the most comfortable because it tends to 'flutter'. It wasn't impossible to dive, but certainly not the most comfortable.(not compared to for example a balanced adjustable paired with a legend or something similar or even my cyklons)

But because one of my old cyklon first stages is so beat up, I wondered if I figured I could pair the xstream with the cyklon second.
Now I know that the mk3 is the only x-stream poseidon endorses with the cyklon seconds.
My poseidon hoses do have these opv nibs on the end of them so in theory shouldn't a first without an opv work just as well? I also read about some issues in earlier x-streams with wear on the diaphragm by people who used to pair the x-streams with cyklons and cranked up the ip. Is this also the case for the mk-2 deeps?

I've gotten the cyklon tuning down to a tee and love them so much, I'm just not ready to accept the x-stream second stage into my life

While there is certainly the matter of personal taste, when it comes to regulator breathing, I can only imagine that your Xstream had been poorly tuned; wasn't well-maintained; and that its second stage possesses a very wide range of possible adjustments -- from a potential 0 to100 mm w.c., though it will -- realistically -- tend to free-flow a bit below, say, 28 mm, and pose a breathing effort above, about 40 mm. That "fluttering" you had mentioned can also a function of tuning. Mine are typically set anywhere between 28 and 30 mm w.c. and breathe effortlessly.

Dollars to doughnuts, your second stage had been "de-tuned" near or above 40 mm w.c., which would account for its poor breathing. The IP may also be off or even drifting.

That said, I have used Cyklons, on occasion, with even the earliest Xstream models, with and without the later integral OPV (your Cyklon second is downstream after all; isn't even an issue) -- without any unusual wear and tear to the diaphragm, which is truly tough as hell. In almost twenty years of using them, I have only replaced the part perhaps once, just as a precaution, and only because I had one on hand.

Depending upon how old that second-hand MK2 first stage is -- whether its serial number is below 310001 -- which I expect it may be, I would recommend the 4826 Upgrade Kit (which contains five or six parts: some new; some outright replacements), regardless whether you continue to use the Xstream second stage; or crank it up, for the Cyklon.

It had been considered a "mandatory" upgrade, by the folks at Poseidon, some years back . . .

 

[Caveeagle]

So, what can you “tune” on an Xstream second stage other than the trigger point of the servo. Valve? I’m always happy to learn, but as far as I know you set the IP on the first stage, and there is only one adjustment you can make to either an Xstream or Jetstream second stage.

While there is certainly the matter of personal taste, when it comes to regulator breathing, I can only imagine that your Xstream had been poorly tuned; wasn't well-maintained; and that its second stage possesses a very wide range of possible adjustments -- from a potential 0 to100 mm w.c., though it will -- realistically -- tend to free-flow a bit below, say, 28 mm, and pose a breathing effort above, about 40 mm. That "fluttering" you had mentioned can also a function of tuning. Mine are typically set anywhere between 28 and 30 mm w.c. and breathe effortlessly.

Dollars to doughnuts, your second stage had been "de-tuned" near or above 40 mm w.c., which would account for its poor breathing. The IP may also be off or even drifting.

That said, I have used Cyklons, on occasion, with even the earliest Xstream models, with and without the later integral OPV (your Cyklon second is downstream after all; isn't even an issue) -- without any unusual wear and tear to the diaphragm, which is truly tough as hell. In almost twenty years of using them, I have only replaced the part perhaps once, just as a precaution, and only because I had one on hand.

Depending upon how old that second-hand MK2 first stage is -- whether its serial number is below 310001 -- which I expect it may be, I would recommend the 4826 Upgrade Kit (which contains five or six parts: some new; some outright replacements), regardless whether you continue to use the Xstream second stage; or crank it up, for the Cyklon.

It had been considered a "mandatory" upgrade, by the folks at Poseidon, some years back . . .

 

[Bigbella]

So, what can you “tune” on an Xstream second stage other than the trigger point of the servo. Valve? I’m always happy to learn, but as far as I know you set the IP on the first stage, and there is only one adjustment you can make to either an Xstream or Jetstream second stage.

Yes, it is admittedly a "single" setting, after a fashion; but the sensitivity of the second stage can be tuned, across that "useful" spectrum from 28-40 mm w.c., by screwing the valve tube towards or away from the diaphragm, depending upon the desired setting, with a hemostat. If the reading is too high, rotate the valve away from the diaphragm; if the opposite is true, rotate towards it.

Alternatively, there is a method to "field" adjust the Xstream second stage in a bucket of water (see attachment), which is commonly done for minor adjustments to cracking effort while remote, should there be some issue.

While the IP is generally a simple adjustment, readings are taken at two pressure settings (200-300 bar); and a final adjustment, if necessary, done at the lower pressure, about 20 bar. Without going further into the weeds, I have included "Field Repair Instructions" and "final adjustments" excerpt from the service manual . . .

 

[Caveeagle]

Yes, I am well versed in how to adjust the servo trigger point. I have All the equipment. Manometer etc. I typically set mine with the water dunk method and then check them with the manometer.

I was confused by your statement of “a wide range of adjustments”..

There is a ton of mythology and misinformation floating around regarding poseidon regs. I am happy to learn new tricks, but keep the reality check set to high.

 

[Bigbella]

I was confused by your statement of “a wide range of adjustments”..

What I meant, by a "wide range," was that extreme capacity for making the breathing either excessively laboured, at about 40 mm w.c.; or, else, air delivery blowing out the back of your head (a common Poseidon complaint), much below 30 mm. There's a happy medium somewhere; and I keep mine just short of free-flow, a bit like that of my Cyklons.

Theoretically, a second stage adjustment can be made of the Xstream anywhere from 0-100 mm w.c. -- a wide range -- according to the current manual; but any realistic setting, still remains somewhere between 28-40 mm w.c. I have worked on them for years and am frequently surprised by the wonkiest settings that I see, when I take an initial reading, before disassembly . . .

 

[tbone1004]

my experience with the flutter at shallow depths is that it usually occurs when the IP is too high. If you actually get the IP all the way down where it is supposed to be, you can sip on them and I don't have flutter anymore.

 

[Bigbella]

my experience with the flutter at shallow depths is that it usually occurs when the IP is too high. If you actually get the IP all the way down where it is supposed to be, you can sip on them and I don't have flutter anymore.

The lion's share of Xstreams that I had serviced, in the last couple of years, had IPs nowhere
near specifications; were generally quite high; and I cannot quite understand why that was the case. With the exception of one, that ended up having a worn seat, none of others drifted after the IP was set. All that was required was an Allen key and an IP gauge. What's the mystery?

All complained of that "flutter," by any number of names -- some not repeatable in polite company . . .

 

[Joris Vd]

my experience with the flutter at shallow depths is that it usually occurs when the IP is too high. If you actually get the IP all the way down where it is supposed to be, you can sip on them and I don't have flutter anymore.

Just checked, they are indeed set at 9.5 bar... Lowered it down to 8.5. Gonna dive them tomorrow to see what if it had any noticable effect. I also ordered a new needle valve and purge, because of the purge being worn and depressed deeply. Just a bummer since the seller garantueed it was serviced by a licensed tech in January. Seems hard for me to believe he wouldn't replace a purge that's basically at the end of it's cycle.

On a good note the serial number is in thé 400000 range so should be upgraded.