Scubapro balanced adjustable second stage freeflowing

[MarkH]

So finally all the parts I ordered came in (2nd stage overhaul kit, including another s-wing poppet, curly-foot levers and a new plastic orifice). After assembly, I'm still having the same issues. I can't get the second stage to stop freeflowing unless I turn in the adjusting knob almost all the way. It seems like it's on a hair trigger. Sometimes I can get the air to stop hissing out, but then when I take a breath, it starts hissing again. I turn in the knob 1/2 turn and it stops, until I take another breath and it starts hissing again and on and on... If I tap the housing, it starts leaking. If I touch the end of the adjusting knob it starts leaking. If I shake the reg it starts leaking. I tried setting it up with it's original 1st stage with its lower IP (125 psi). Still the same issues. I tried mixing and matching different orifices, poppets, adjusting knobs. Still the same. I tried converting my other 109 second stage to a balanced adjustable using the same new parts. Still no luck. Sometimes when I had it adjusted a certain way, the air delivery would come out in fast pulses like a machine gun. I've never had that happen before with any reg. I suspect it's something to do with the balance chamber. I set up my 109 back to it's normal non-balanced configuration and that went fine. At this point I think I'll cut my losses (about $300 in parts, mostly shipping) and give up and go back to my more reliable Conshelf.

 

[axxel57]

Still the same spring?
If you like, send me a PM and I'll send you a new spring and a new Balance Chamber for free........
Believe me , the BAs are very reliable........

 

[MarkH]

Still the same spring?
If you like, send me a PM and I'll send you a new spring and a new Balance Chamber for free........
Believe me , the BAs are very reliable........

Thanks for the generous offer, but I think I finally cracked the case today. I have access to a lathe at work so today I machined some plastic washers and a new, longer balance chamber with a slightly-smaller opening. I wasn't considering diving with the homemade balance chamber, but I thought it might help for diagnostic purposes. First I tried the washers. I made one thin one (about 1mm) and a thicker one (about 2mm). I first tried the thicker one. I put it between the balance chamber and the spring. And it worked! I was skeptical at first about the suggestions on this thread to add shims to the spring since I assumed that's what turning in the adjusting knob does, but adding shims changes the tension on the spring without changing the balancing chamber's position so the effect might be different than just turning in the knob, which moves in both. With my thicker shim/washer, I was able to adjust the orifice to not leak when the adjusting knob was turned all the way out. After that success I tried the thinner washer, but that didn't work. The reg was up to its usual unstable freeflow tricks. So I went back to the thicker washer and I think it's good now. I didn't even get to try my homemade balance chamber (fortunately). The cracking pressure seems to feel a bit higher than my Conshelf, but once it cracks it seems to deliver more air. I'll take it for a dive this weekend and see how it feels underwater. So after all, I guess it was the spring and it didn't take much extra tension (2mm) to correct it.

 

[Mobulai]

Good on you for giving it one more try, and glad it finally works

First I tried the washers. I made one thin one (about 1mm) and a thicker one (about 2mm). I first tried the thicker one. I put it between the balance chamber and the spring.

For future readers with no access to a lathe, McMaster has washers that fit as spring/bal chamber shims for SP regs and compensate well for weakening springs

In any case, since the 218 was added to the later G250V, then if you can get any reg that used the 216 to tune properly with the 218, you should be fine. Occasionally, I've had weak springs that I shim with a ring like the G500's 11.500.029. There is a McMaster equivalent: 95630A217.

(For context the 218 is a stronger version of the 216 -ie same size- that has higher spring constant; that’s why the 250v is way less prone to violent freeflow than the normal 250)
I ordered a bunch of these washers to tinker with some of my g250s