G250V - unusual tuning problems

[aoumi]

Hi,

I have 2 G250v's that I got new back in 2012. I like these second stages for their smooth breathing. But, I'm having some problems tuning them that have left me scratching my head.

I've overhauled them 1 or 2 times in the past, with no problems tuning them to about 1.1 inches of water for inhalation effort. But this time, after coming back from a trip overseas, I decided to test the cracking effort first before servicing.

Both of them were lower than 1 inches of water. No problem, I serviced one, setting the orifice at 1 1/2 turns back from being fully screwed in to set the initial position of the orifice, and tested, as it was due for a service.

When tuning, I found I had to screw the orifice in a bit more than normal in order to get it anywhere near spec (1 inch of water minimum). So much so, it had extreme lever rattle. Ok I thought, the spring is 8 years old. Let's replace that.

Tried 2x new springs, (01.020.218). Same problem. I also had a couple of new 01.020.216 springs for a S560, so I tried one of those. Still the same problem, orifice needs to be screwed in further than in the past to get in to tune, which causes excessive lever rattle.

I had an 'Aha' moment. I had removed and re-installed the lever on the 1st of my 2 G250v's, and maybe bent it a little. So replaced the lever with a new one. Same problem persisted.

At this point, I gave up on the 1st of my G250v's, and started looking at the 2nd one. The 2nd has never had the original lever removed or touched at all. Tried various new springs in this. Exactly the same problem.

I think from memory, I then swapped the balance chamber from my S560 (same part number) and gave that a try. Still the same problem (tuning lower than 1 inches of water, screw in the orifice a bit to fix, which gives severe lever rattle).

I'm really scratching my head now on this one. In the past, neither of these 2nd stages had issues tuning, and would tune not far from the initial setting of the orifice (backing out 1 1/2 turns from fully screwed in), and would be within spec with no of almost no lever rattle. I can't think of anything else to change/try.

(The only other piece of info I can offer, is that on my last boat dive trip in the hot and humid 33 deg C, 78% humidity), both these regs were out baking in the sun on the back of the boat for quite some time. Would the heat have damaged them somehow?)

Any ideas?

Thanks

 

[Still Kicking]

Whats the IP from 1st stage?

Can you post some pics of 2nd stage internals?

 

[aoumi]

IP from a newish MK25 is at 135 psi. I'll post some photos of the internals later when I get a chance

 

[rsingler]

I'd look at the orifice/knife edge under a loupe. I'll bet you'll see some irregularities. When you polish them out with some Micromesh, you'll be able to get your cracking effort with much less spring pressure. And without the lever drop.
Sad to say, that's why the G260 is such a significant improvement over the 250 ‐ lever height adjustment is separate from spring tension.

 

[АлександрД]

I'd look at the orifice/knife edge under a loupe. I'll bet you'll see some irregularities

It could be even more simple...
Need to check valve seal. I suspect, it could be dented from orifice, and require other force to seal it.
Also it could be due to overheated of 2nd stage, and sealing were soften.

 

[Kupu]

Just another thought in addition to ideas above, were the poppet & balance chambers tested to verify they are working properly?
Seal the low pressure seat orifice (I use tip of finger) and then install the balance chamber without spring on the poppet. After a light push down on the balance chamber, it should spring back after releasing.

 

[Open Ocean Diver]

Both of my G250V’s with the orifice turned in to stop any leaks, lever is high and touching the diaphragm they both crack @ .7 to .8, if I adjust the orifice further in to increase resistance I get lever diaphragm separation and you feel it when breathing dry. I just don’t know how much lever diaphragm separation is acceptable. If I adjust them to 1 H2O I have very little purge. IP 140

 

[lexvil]

Lever height is the main factor you need to consider with that adjustment (orifice) then put in a new seat and use your adjuster knob to stop the leaks, if any. If that doesn’t work you may want to change the poppet and see what happens, once you get them working sell them and buy a g260 or a D420, the 250 is a pretty simple animal and I can’t imagine anything sitting in sun could damage other than the seat.

 

[davehicks]

Lever height is the main factor you need to consider with that adjustment then put in a new seat and use you adjuster know to stop the leaks, if any. If that doesn’t wort you may want to change the poppet and see what happens, once you get them working sell them and buy a g260 or a D420, the 250 is a pretty simple animal and I can’t imagine anything sitting in slug could damage other than the seat.

If you find a Slug in your regulator be sure to give it a good rinse before diving.

 

[rhwestfall]

Did you use ScubaPro seats, or something else? If the seat head is not the same thickness, you will have problems.