Old Kirby Morgan metal or Usless Divers Conshelf type second stage

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muddiver

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Ok, stupid question time. I hope DA Aquamaster reads this. Anyway, I just scored an old Kirby Morgan Superflow metal adjustable second stage scuba regulator and I spent the afternoon and evening two weeks ago Saturday rebuilding it. It is my impression that the regulator is pretty simple to adjust after putting it back together because it either free flows if the valve arm is depressed by the diaphragm, or it doesn't. What gets me is the work of breathing required by this thing compaired to my Sherwood Blizzard, my new Kirby Morgan Superflow 350 plastic second stage regulators or even my Superlight 17K (it has a metal Superflow 350 demand reglator on it).

Has anyone every dive the old metal second stage KM/Conshelf and noticed it being harder to breath than more modern regulators a shallow depths?
 

Fishpie

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The one I have breathes about the same as a well tuned 109.
If yours is hard to breath from there's really only the spring and adjustment tube to suspect as problems, and if the tube is working properly then it's the spring.
 

muddiver

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The one I have breathes about the same as a well tuned 109.
If yours is hard to breath from there's really only the spring and adjustment tube to suspect as problems, and if the tube is working properly then it's the spring.

Are you referring to the inlet valve spring, or the adjustment pistion spring? I notice this one came with an additional spring in the adjustment assembly that was nested inside the main spring.

---------- Post Merged at 02:04 PM ---------- Previous Post was at 01:55 PM ----------

I just figured it out. Compairing the blow-apart for the scuba regulator with the Superlite 17K helmet regulator shows that there are only supposted to be two springs total. I guess someone who worked on it before I recieved it must have thought more is better.
 

couv

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Hey Mud,

I have a bit of time in a KMB10 - it had a great KM metal regulator. It's hard to make a direct comparison because as you know it had an oral/nasal mask; but if I were to guess the work of breathing was probably the one of lowest, if not the lowest, of all the regulators I've used.
 

Fishpie

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I couldn't remember if they have a spring loaded piston or a pneumatic one like the old Oceanic Deltas.

It would make sense that it doesn't breathe easily if there is too much pressure being put on the seat shaft by the piston.
If the main spring under the seat has weakened that means that the adjustment nut would need to be slackened to move the seat closer to the orifice which could lower the lever height......does your reg rattle?

I have had some plastic KM 2nd stages (badged as SeaSport) with weak main spring and lever height issues.
 

muddiver

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Fishpie, no rattle, everything is tight.

couv, its the same regulator with a flanged mouth peice tube to mount the mouth peice on instead of the threaded tube that goes through the frame to the retaining nut in the oral nasil.

I broke down and called KM and talked to a tech there. It turns out the scuba regulator has a spring on the inlet valve side and only one on the adjuster side. The helmel regulator does not have a spring on the inlet valve side, but does have two nested springs on the adjuster side.

Me thinks someone use a helmet rebuild kit/parts on this scuba regulator at one time.
 

couv

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Thanks for the update, Mud. Keep us posted on the rebuild and how it performs when you're done.
 
https://www.shearwater.com/products/swift/

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