Scubapro MK5 Piston

[Ghost95]

Morning all, hope you are well.

I have acquired 3 SP Mk 5's that I am playing with. They are all the early model with 2 LP ports. What's interesting is that they are 3 variations of the new model.

One of these has the mid range 3000psi yoke and a turret screw. The other two have the C-Clip holding the turret on. I am probably looking to add a turret with a screw to one of the C-Clip ones. I've tried swapping parts and it looks like I just need a screw turret. If anyone has an old 2 port turret with a screw retainer, keep me in mind.

Anyway, I disassembled these and I found 3 different piston designs. In the photo the piston on the left is from the screw turret model and the center and right are from both of the c-clip models.

Is there anything special about these pistons? Are they more desirable or anything or are they just run of the mill parts variations that I don't need to worry about keeping all original? I just found it interesting to find such a variation of a major part.

Also when I get to the 109 that came with one of the c-clip models I'll post what I found. It was very strange with the parts. Defiantly not one of my best ebay purchases. Good thing it wasn't much.

Let me know if you see anything special about the pistons that I need to keep together for posterity.

Have a good day.

 

[rhwestfall]

Did you get a ball / spring poppet assembly? That is real old. Upgraded easily with a g250 upgrade kit.

 

[Ghost95]

Yes, There was a ball in the 109. I was wondering if it was just parts somebody threw into a display or something. It came with the first stage that had the piston on the right.

 

[Ghost95]

Here is what was inside the 109. Minus the lever that's not pictured.

 

[Angelo Farina]

The left-side piston is the more modern one, providing larger air flow.
At the time I purchased my second MK5 (1978) I noticed that the piston was different from the one of my first MK5 (purchased in 1976), so I ordered the new part and swapped it on the older unit.
Perhaps I still have somewhere the old piston...
Regarding the 109, I warmly suggest that you convert it to a 156BA, mounting the latest S-wing piston of the G260, and the spring and balance chamber of the G250V.
This makes the reg sligthly smoother, with less cracking effort and better venturi effect. And the seat lasts longer, allowing for doubling the service interval.

 

[Ghost95]

The left-side piston is the more modern one, providing larger air flow.
At the time I purchased my second MK5 (1978) I noticed that the piston was different from the one of my first MK5 (purchased in 1976), so I ordered the new part and swapped it on the older unit.
Perhaps I still have somewhere the old piston...
Regarding the 109, I warmly suggest that you convert it to a 156BA, mounting the latest S-wing piston of the G260, and the spring and balance chamber of the G250V.
This makes the reg sligthly smoother, with less cracking effort and better venturi effect. And the seat lasts longer, allowing for doubling the service interval.

Thanks for the info. I kind of figured the left was more modern based on the second that came with it. The serial number on the 109 was 7 digits and not 6 like on the 109 that came with the piston on the right. Also it had the heavier yoke and a screw retained turret. What is interesting is the center piston with the cone shape around the piston shaft. The regulator that that piston came out of didn't have a second attached.

 

[Couv]

I disassembled these and I found 3 different piston designs.

I've never seen a piston like the one in the center.

If anyone has an old 2 port turret with a screw retainer, keep me in mind.

@Ghost95 I have one I'm willing to sell, but it will have to come with the cap (the part that mates up to the body) else I'll be stuck with an orphaned cap. (PM me)

This is not absolutely a requirement, but you might also consider this:
Store | Vintage Double Hose (I have a couple of those too.)

Is there anything special about these pistons? Are they more desirable or anything or are they just run of the mill parts variations that I don't need to worry about keeping all original? I just found it interesting to find such a variation of a major part.

The most desirable piston is yet another iteration. It has a stepped (shouldered) piston like it's younger brother the MK10. You'll also notice that some pistons have a smaller i.d. than others.

Credit to @cbmech2 for this picture:

See this thread for a discussion:
Sp mk5 piston