Picked up a regulator set, how did I do?

[NightShade00013]

So I have been trolling for a while trying to find something I can rebuild myself but isn't going to be a major pain. I came across a MK20 with a G250 set ended up paying 110 shipped and tax. I don't think it has a gauge or console with it but have my eyes on something though they didn't accept my offer so going to wait till the end to throw a bid in on it if my dive shop doesn't have something cheap sitting around. I think this will pair well with my BCD with an Air2 system as well.

Was looking at a MK17 with a S550 and console included but 250 plus shipping seemed a bit steep and you can see clear corrosion on the hoses near the first stage regulator so I was very leery about it for that reason as well.

Guess I need to find some absolutely needed tools to rebuild them as well now that they are one the way.

One thing I was wondering is that if the piston on the MK20 is metal and not the composite version in the MK25 is it worth upgrading right away or easier to wait? I was reading about some complaints for the MK25 piston wearing faster/splitting into two pieces so if it's not worthwhile and it hasn't already been done I will probably just stick with the metal one.

 

[runsongas]

check if it is the rounded or knife edge piston, knife edge has a better lockup and the upgrade can wait longer.

 

[halocline]

check if it is the rounded or knife edge piston, knife edge has a better lockup and the upgrade can wait longer.

All MK20 pistons are rounded to some extent, none of them have a sharp knife edge like the MK5/10/15. But you do have a point that the there are different pistons in various generations of MK20s and they have a big impact on how well the reg works. The early ones have a solid stainless piston that works fine. The middle ones have a brass-tipped piston that works horribly and should be upgraded. The later ones had the composite piston with the stainless shaft and the plastic head, same as the MK25. Those pistons lock up great, but they do have one defect; there's an internal o-ring that is not supposed to be replaceable, and eventually will fail, causing a leak.

But.....getting back to the original question, if you bought a MK20/G250 for $110 you got a great deal regardless of the piston that's in it. If you find it has the early stainless piston, just leave it as is, but if you have the brass one, get the MK25 piston. It will likely last many years before there's any problem with that internal o-ring, and you can replace it if you're a bit mechanically inclined. SP techs wouldn't do it, they'd just sell you a new piston. But it's nothing to worry about.

 

[runsongas]

my recollection was that the brass piston was more rounded and the SS and composite pistons had a design closer to the old knife edge and hence why they performed better?

 

[halocline]

my recollection was that the brass piston was more rounded and the SS and composite pistons had a design closer to the old knife edge and hence why they performed better?

The brass tip looks more rounded, but they all use the same seat and seal in the same way. None of them are sharp like the earlier MK5/10/15 pistons which are designed to cut into a flat or slightly conical seat. The MK20/25 is a completely different seat design, it looks like a cup, and the rounded (or blunt, I guess you could say) piston pushes against the side of the 'cup' without cutting into it.

 

[Perryed]

MK 20`s have been known to blow up if the yoke was over torqued on a rebuild. This can crack the case. I got one and Scubapro will upgrade for no cost. Check about recalls on the net and you can tell if yours has been updated if it has 2 slots where the yoke joins the body of the reg. 3 slots and it needs the upgrade.No injuries or deaths reported but it can be rather disconcerting to have your 1st stage blow up under water.

 

[happy-diver]

Scubapro MK20 upgrade to MK25 SCUBABOARD


I so admire those that continue and are able to eloquently utilise the term disconcerting

 

[buddhasummer]

If by disconcerting you mean freak the f...k out...

 

[Perryed]

Yes, I believe that is the definition. And not just the diver, but those in the vicinity also. I think several people did an octopus imitation and inked.