G250v feels like it has 2 stages during the inhale with reg in either pre-dive or dive mode

[crofrog]

I have 2x G250v's on MK25 (actually halycon) second stages that I use as doubles, they have about 70 dives on them now, but they've done this since new. Where when you very lightly inhale (like sipping air) you have one stage, and then as you increase your pressure it sorta stays the same and then it like gets over a "hump" and catches up to your demand. This happens even in "predive" on the venturi. It's never affected anything and I don't notice it at all diving but I recently got a 3rd set for stage bottles and it breaths buttery smooth so it had me looking at this.

The cracking pressure is tuned to about 1.2inH20 and the IP is 135.

Any ideas what could be causing this "stickiness"

 

[Nemrod]

The G250 has a particularly strong Venturi so I am not surprised you feel it come in but I do not think it should be so pronounced. I think at last count I have six G250 second stages (pre HP type) and they are smooth but definitely progressive. I just bought a new Mark 17 and (two) G260 second stages and I noted right away they were not as smooth as my G250 regs and that there seemed to be a step though not as noticeable as you describe, just kind of stiff. I finally decided to just tear them down and adjust them to the manual. I also set them to be on the verge of flow with the knob fully out. Regreased everything and set the lever height. The step is gone and they are now smoothly progressive. They seem to set up now just over 1.0 inches on my Magnehelic when I have the knob turned in to stop free flow plus a skosh, about 1/2 turn I guess.

You might check the feet on the lever that insert into the valve body that they are both parellel. You might inspect/replace the O-rings and lube them on the balance chamber. Maybe install new LP seats since you have them apart and set the regulators up to begin to flow with the knob fully out. Ensure that the lever just contacts the diaphragm as lever rattle/free play is not desirable. Per the manual you are shooting for 1.0 inches cracking effort.

James

 

[crofrog]

The G250 has a particularly strong Venturi so I am not surprised you feel it come in but I do not think it should be so pronounced. I think at last count I have six G250 second stages (pre HP type) and they are smooth but definitely progressive. I just bought a new Mark 17 and (two) G260 second stages and I noted right away they were not as smooth as my G250 regs and that there seemed to be a step though not as noticeable as you describe, like they were shifting gears. I finally decided to just tear them down and adjust them to the manual. I also set them to be on the verge of flow with the knob fully out. Regreased everything and set the lever height. The step is gone and they are now smoothly progressive. They seem to set up now just over 1.0 inches on my Magnehelic when I have the knob turned in to stop free flow plus a skosh, about 1/2 turn I guess.

You might check the feet on the lever that insert into the valve body that they are both parellel. You might inspect/replace the O-rings and lube them on the balance chamber. Maybe install new LP seats since you have them apart and set the regulators up to begin to flow with the knob fully out. Ensure that the lever just contacts the diaphragm as lever rattle/free play is not desirable. Per the manual you are shooting for 1.0 inches cracking effort.

James

Thanks I have a pair of g260/mk17s and they’re buttery smooth. I’ll check the things you mentioned.

Shifting gears is how I’d describe it.

Thank you

 

[Nemrod]

The G260 have the Micro-adjust feature, the G250V do not of course. So they do set up a little different. I assume you have googled and found the manuals? When making adjustments on the orifice be sure to depress the purge button/lever so as not to cut your (new) seats. Hopefully the expert Scubapro tuners will be along shortly.

James

 

[buddhasummer]

I have a manual, DM me if you want it.

 

[buddhasummer]

And yes, make sure proppet O rings are nicely lubed and balance chamber is clean and not full of gunk.

 

[buddhasummer]

Also, Check lever plastic sleeve andmake sure it's not nicked/damaged etc as the lever can catch.

 

[buddhasummer]

You want smooth lever action.

 

[Geo7]

Hi all,
I feel this thread still has a lot of potential to provide valuable insights. The OP has touched upon a common phenomenon I think, and I am not sure what the cause is.

This observation of the Halcyon reg (aka Scubapro G250V) mirrored what I have observed on 1-2 Atomic seconds, and on a S620ti.

Not sure if we are talking about the same effect, so that's the first thing to clarify in this thread, and then find the cause and remedy: The first time I noticed this on the Atomic, it felt to me like an uneven separation of the orifice from the LP seat. As if the orifice was not straight, or the poppet was not lifting straight. Basically, upon slight inhalation there was a slight hiss/flow, and upon a further lever depression the orifice fully separated and gave normal flow. Not a big deal, I bet some people would not notice or care. But it was not smooth.

Back then I figured it must be a side effect of the Atomic seat saver, but then I got 1-2 super-smooth breathing Atomic regs. Perhaps better lubrication or newer parts with better tolerances, I thought. Then I had a super-nice and smooth breathing S620ti, and after neglecting it on a trip and travelling with it, it also showed that two-phase breathing. I still have to service it and re-check.

My approach would be to clean all parts and look at critical parts with a loupe and re-assemble. But I wonder if we can narrow down the potential cause, so my question is, who else has seen that, and does anyone know what it is? I am ruling out the first stage, unless someone thinks otherwise.

Potential trouble-shooting remedies:

-just cleaning and lubricating and careful reassembly
-different poppet insertion techniques?
-new lever sleeve
-new LP seat
-for Scubapro: new LP seat and new orifice (delrin, like original).
-for Scubapro: switch to metal orifice
-for Atomic: new orifice sleeve
-new balance chamber
-new poppet-o-rings (that seal in the balance chamber)
-new lever

What do our reg guru's think?

 

[buddhasummer]

I too have experienced this phenomenon on an Atomic and a D420.