Question SP G250/109/BA Orifice variations?

[Mobulai]

Found it after some search keywords refinements, thanks for that heads up and a for remembering @rhwestfall


For completeness sake:

I had gotten a G250 off the used market, that had "official" serviced labels on it (the place used a custom hose protector with the shop name, and date of service). I quickly serviced it, and just couldn't get it to work.... As I looked at my parts supply for options, it dawned on me that the only times I had seen 109/156, g250 & G250v orifices, they were stainless steel or plastic, and this one wasn't.... It was then that I compared it to a known one, and SURPRISE!!!!!, it is shorter.

As I said, I don't have my schematics handy, but the only other "brass" orifice I have seen [edit - I thought I have seen] was in a G200/G200b.

Anyhow, here are the two:

Proper height:


View attachment 378703


Problem height:

View attachment 378704

YMMV.

I think the orifices on my 109s and G250s are all chromed brass, not stainless steel. I guess some of them could be stainless, but I know I've had a few with the chrome pitted.

I think your assumption that the G250V orifice is bottoming out at the same depth may be your problem. All of the issues you are having could be explained by the orifice bottoming out deeper. If they are bottoming out the same I believe the difference in the length of the orifice should be the same as the difference in the depth them bottomed out. If you have a set of digital calipers available it might ease your mind to do the measurements.

I could not get the "short" original orifice to work with the s-wing poppet... you might have a "bad" poppet..

Another "issue" I had was the balance chamber, which at times, despite proper lube, was sticking on the poppet stem. I may have gone back to the original, or another one. Is it free moving on the stem? The test is to put the poppet, seat down on a smooth surface, put the balance chamber on it, and lightly push it down. When you release it, it should come back up on it's own......

It's hard diagnosing over the internet..

 

[rhwestfall]

2016.... Wow....

 

[Duglum]

@Mobulai: Scubapro G250 Orifice Extractor Tool

There you go.. if you have access to (someone with) a 3D-Printer. Most overengineered chop stick in existence probably, but it works perfectly. And it absolutely cannot damage the knife edge.

 

[buddhasummer]

Ah awesome! i actually have that buried somewhere — just default to pulling it with a plastic crochet hook or with a wooden dowel
should get it out of its hiding place

A non coated wooden chopstick works a treat too.

 

[buddhasummer]

G260 knob in a G250? Are you sure? Given the G260 uses a pin to hold it in place you could not secure it in a G250.

 

[Nemrod]

I just use a brass or plastic tube as a pusher. The ID of the tube is greater than the volcano OD so there is no danger of damage.

 

[Kupu]

G260 knob in a G250? Are you sure? Given the G260 uses a pin to hold it in place you could not secure it in a G250.

I had the thought that it would be nifty to have micro adjust capability retrofitted into older second stages and so installed a G260 adjustment knob into 109 just to see if I could get it to work on the bench.
It got as far as seeing that the G260 knob does fit but would require a spacer to function and did not take it any further...

 

[Mobulai]

@Mobulai: Scubapro G250 Orifice Extractor Tool

There you go.. if you have access to (someone with) a 3D-Printer. Most overengineered chop stick in existence probably, but it works perfectly. And it absolutely cannot damage the knife edge.

View attachment 859556

I love the presence of a handle on it

 

[Mobulai]

I have no clue on that except what Kupu shared back then, haven’t opened my(any) 260s yet..

G260 knob in a G250? Are you sure? Given the G260 uses a pin to hold it in place you could not secure it in a G250.

Again for completeness sale, a very interesting project:

I went back and played with the G260 adjustment screw, but leaving the orifice alone, and was able to bring the cracking pressure down to .6, up to maximum of .8 when inhaling as much air as possible. No freeflows despite repeatedly pressing the purge all the way down. A personal best for lowest cracking effort, just for fun.

Playing around with the idea behind G260 adjustment knob screw, I wondered if it could be retrofitted into a G250/156 etc. The knob can be screwed into the 156 barrel, but it is not compatible enough to work. The location of the threads prevents the G260 knob from reaching deep enough to make contact with the 156 spring pad, about 1/4 inch difference. Not that it is at all practical, but it would be interesting to machine or print a copy of the G260 knob with dimensions allowing use on G250, and see how the two versions compared when tuning.
View attachment 528907 View attachment 528908

Correction, I tried the G260 knob on a 109, not 156. The idea has been stuck in my head and I realized that replacing the 109 spring pad with a balance chamber will add length to the 109 poppet assembly and allow contact with the G260 knob. Not an option when using the the shorter spring of the 156, but should be easy to make a spacer to set between the 156 balance chamber and adjustment knob.

Only way to get this out of my head will be to give it a try next time I get a little bit of free time. It would be really neat to have it work and see a measurable difference...a matter of curiosity.

 

[Mobulai]

G260 knob in a G250? Are you sure? Given the G260 uses a pin to hold it in place you could not secure it in a G250.

Just looked a the 260 schematics for the 1st time — shame on me for doing it so late.
I think I see what you’re getting at, but I wouldn’t fully “see it” till I actually see it; will have to wait till Oct tho