solution for D-series poppet seat DIY?

[lexvil]

Dive report for the D420 with the 104 o ring seat;
Did two dives yesterday with the 420/104 first dive on a pony and than as my primary for the second dive, this thing breaths like a dream so far and in the shop dry it lost its original stutters and lifts and breaths like an old D series. I’m contemplating opening it up to see the condition of the seat but more tempted to get a few more hours of dive time on it first, for now this really ups the breathing game of the New D.

 

[rsingler]

I've tried to duplicate your results, and am running into a little leaking at higher IP's. I bought 50 Shore silicone as well as some X-profile 60 Shore Buna and 70 Shore Viton.

The X-profile seemed to grab the poppet stem the tightest, but leaked at 150psi. I'll take the reg apart and look at the poppet tonight.
The 50 Shore silicone was working great until I tried to increase cracking effort a lot, it then wouldn't seal at all. Again, I'll disassemble tonight to find out where it's leaking.

One question: where's the 1x2.5mm oring in your reg? I can't tell from your description. I put mine in the little groove of the poppet cap (on the side of the oring outside the IP compartment). I may add a second on the inside where the poppet stem has that little step.

I was so hopeful, but am currently a little discouraged. I may add some glue, too.

 

[Kupu]

Locate the 1x2.5mm oring as shown. The regulator will not seal unless the 1x2.5mm oring is installed first, followed by the 104 oring seat.
After putting on the cap and nut, do not overtighten the nut, which will result in leak. Best results for me have been with the nut being finger tight plus approx 1/8 turn.

 

[lexvil]

I have mine on the top of the 104 and under the cap on the 420, basically just replaced the metal reinforced seat with the 104.

 

[rsingler]

Thanks, guys.
I'll report back.

 

[rsingler]

@Kupu, I think you just became the D-series star of the decade. I've reproduced your results, and tuned at both low IP (125psi) and high (150psi) to well below spec, with no leaks. At 125-135, I was able to consistently get 0.55" WC. At 150, the best I could do was 0.7". All this with the 50 Shore red silicone 2-104 o-ring.

As you suggested, my leak went away when I put a small oring on the inside of the poppet. Since the shaft diameter was larger, I used a 1 x 3mm oring. But I also left the 1 x 2.5mm oring on top of the 2-104, under the cap. I think this may have removed the emphasis on how loose the top nut had to be.

I didn't have as good luck with an X-profile 2-104, despite a tighter fit around the poppet shaft.

I think the small 1x3 did not provide a good dynamic seal with the X-profile above it.

Best of all, with the soft silicone o-ring, tuning for a high cracking effort did not create a leak. There's no real reason a diver should actually want a cracking effort of 1.5" on the dive setting, but it shows that you can have high spring pressures on the poppet without deforming the o-ring sandwich and getting a leak.
Interestingly, though, I couldn't get above 1.6" even with the spring fully compressed with an extra shim and low IP. The 50 Shore is just too compliant to seal more tightly. A higher duro would doubtless help, at the cost of a similarly higher bottom limit.

@Kupu, you da man!

Scubapro D-400
World all-around performance winner:
Doesn't breathe wet like the Pilot when inverted
Low cracking effort unsurpassed
Same effort in all positions
Huge gas flow​

Compromises?
Slightly increased exhalation effort compared with the D420. Not as effortless in the standard diving position as the D420. A PITA to service, for some.

Courtesy of @John in GA, I've been provided with a whole new abrasive technique to restore that delicate knife edge. Look for a restoration thread one of these days. Of course, between a sharp knife edge and the Kupu seat, everybody will want to dive D-400's, and the eBay price will skyrocket. So get 'em now while you can!

 

[lexvil]

Now try it on the 420.

 

[rsingler]

 

[Kupu]

Very happy to hear of good results @rsingler.
I appreciate the feedback and additional information provided by both you and @lexvil.

 

[lexvil]

The part I really appreciate on this change as far as the 420 is it’s dry behavior as I now can get a feeling of the in water performance without being in the water, like the D400. As tempted as I am to open it back up to look at the seat I want to give it more run time to make sure it isn’t damaged by the orifice (I don’t expect it to be because of the orifice material of the 420) which leads me to wishing I had some internal contacts at SP to ask if they had done any similar research.