D420! How about that?

[buddhasummer]

Yes, that is what I was thinking, and @halocline 's technique is worth a try:

Could be on to something, I just remembered an earlier post I made which could well relate to this:

"It seems if I turn it in and then out or vice versa cracking changes a little more consistently with what you'd expect. Is something sticking?"

 

[Open Ocean Diver]

Just a note: rsingler fixed this problem on the D400 with a silicone impregnated shim installed between the spring and the plastic spring cap adjuster which makes things very slippery.

 

[James79]

That's what I get for not fully reading couv's post! Lol

 

[lexvil]

While I can’t say with 100% certainty that this spring bind isn’t a problem I don’t think it’s my problem although I do cycle the reg several times before testing it. I had it consistently at .8-.9 with good enough flow but with Rob’s suggestion on the lever I went ahead and lowered it from about 1mm above rim to just below the rim so diaphragm has about 1mm play before touching the lever, all its done is increase cracking to 1.1” and still takes the same spring pressure to stop flow flow remains ok, maybe a little less.

Here is where I am with this, I’m in doubt that this whole design is a solution to anything I’m likely to encounter, in fact it a solution looking for a problem, IMHO. The G260 is near perfection and incredibly easy to tune, the in line balancing system was nearly perfected with the BA 156 and G250 the introduction of the micro adjustment in the 250HP and S600 refined it, maybe more for the manufacturer because they no longer had to sort springs to get great flow.

I was never a big fan of the D series even though they could be amazingly easy breathers.
I have a C370 that kicks the D420’s but on performance and ease of tuning.

With james79 adjuster tuning in the water may bring this thing around but I have my doubts. Overall with standard designs of the inline balancing of the “S” “G” and “C” series being easily tuned to the point of no thought breathing I’m about to jump off this band wagon.

 

[rsingler]

Just an off the cuff idea.... if the adjuster hex is turning a spring pad, is it possible your wandering tune is from the spring twisting a little with the adjustment, and then straightening with use (if that makes sense.... like the spring pad binding temporarily instead of isolating the rotation of the hex from the spring)?
just spitballing ideas....
respectfully,
James

Part #26 on the schematic above is the piece that should prevent spring binding. If that's omitted on reassembly, you could easily have the spring catching and erratic cracking efforts. Same problem that all but the last D-models had. When they added the white button inside the spring cap, that problem went away. As @Overweighted suggested above, I eliminate that issues in my earlier D's with a graphite impregnated washer. There's a thread on that workaround somewhere.

Just back from the Spiegel Grove. 110' and breathes like a charm! My cracking effort tweak to 1.1" was still a shade light. But it was effortless at depth.

The comments above about the C370 match my observations about the downstream (unbalanced) C350. Scubapro did well with the case redesign. But I'd take issue with the statement that it delivers anywhere near the volume capable with the D420. The two flow paths are markedly different. May not be obvious at 40', but as air density increases, the D420 should be easier, especially with workload.

 

[rsingler]

@tridacna is right, though. The stock Scubapro mouthpiece on the D420 sucks. The ridges are too high and dig into the space between my lips and gums.
I'll switch for my dive on the Vandenberg wreck tomorrow. More to follow...

 

[Couv]

my dive on the Vandenberg wreck tomorrow. More to follow...

Yeah, that's right. Rub it in good. (>_<)

 

[Open Ocean Diver]

@tridacna is right, though. The stock Scubapro mouthpiece on the D420 sucks. The ridges are too high and dig into the space between my lips and gums.
I'll switch for my dive on the Vandenberg wreck tomorrow. More to follow...

I left some skin on the Vandenberg couple years back. I would use your Atomic mouthpiece they are great.

 

[tridacna]

Aqualung Comfo-bite all the way. Now on my 420 too. I hate the SP stock mouthpieces.

 

[buddhasummer]

Aqualung Comfo-bite all the way. Now on my 420 too. I hate the SP stock mouthpieces.

I ditched mine in favour of an Atomic.

If your sticker is off I'd love to see a photo of where your hex key is sitting if it's not too much trouble. It seems mine and Lex's are way down compared to Robs. Thank you.