Intermittent "stiff" breathing on vintage reg

[herman]

Yep, that was me. The problem with the spring was pretty predictable. The IP was stable up to a certain value then went crazy but I could duplicate the problem at will.
An intermittent problem is always the worst, I much prefer something totally fail than have an intermittent problem. Swapping between second stages (primary and octo) when the problem is happening should point out the offending stage. If both seconds are stiff then it's the first, just one second, you have the culprit. I would swap out my octo for a similar performing second to my primary if I my normal octo was one of the normally poor performing octs.

 

[MiddleCoaster]

Thanks to all who have responded so far! I will be in a quarry helping with OW checkout dives this weekend and will try the swap out for the octo when things get stiff on the primary.

The instructor I work with has some tech knowledge and correct tools, so we may tear into the system on Saturday night and re-test it on Sunday once we understand what piece to tear into.

I have a back-up reg available should something go awry Saturday night.

 

[MiddleCoaster]

Quarry diving this weekend to assist with student check out.

When the primary second stage began to breathe stiff, I switched to the octopus, which was fine. Thus, the stiff breathing is a second stage problem in the primary.

Disassembled the second stage Saturday night and found a lot of play in the diaphragm lever. Adjusted the poppet nut to take out almost all the play and reassembled.

Sunday diving, the reg was more sensitive to free flow at the surface, but not unmanageable. Underwater, breathing was easy, but there was just a slight air flow when I (briefly) stopped breathing. Apparently I had slightly over-adjusted the poppet nut.

Disassembled on site between dives and backed off the adjustment just a little and all was fine.

So the immediate problem was the primary second stage lever out of adjustment. Not sure how that might have happened.

When returned from rebuild, the reg breathed fine, and the problem surfaced about a year later. What might cause this?

I speculate either an obstruction or misalignment where the lever attaches to the poppet stem or an obstruction at or swelling of the poppet face would be the likely causes for the lever to become too low over time with respect to the diaphragm.

Another possibility would be if there is supposed to be a washer at the point where the lever attaches to the poppet stem, and the washer broke. It could easily have gone out the exhaust port, and would leave the lever "loose" and therefore too low.

I will examine the poppet face and seat next.

Wish I could get a detailed schematic and parts list for the reg. Greg Barlow -- do you have and would you share such a drawing? AMF Swimaster MR12-II.

 

[Greg Barlow]

Just send me your regular email address via a PM, and I will forward the information that you need.

Greg