Need tips/advice on DIY reg rebuild on MK10 G250/D350

[Mark IV]

Your new MK10 is probably older than the young tech at your LDS, and they are unlikely to have any spare parts needed in inventory.

Actually, Planet Ocean Scuba in Columbus Ga has been a (same owner) dive shop at least since I was in high school, 35 years ago !
And, he's a Scubapro dealer, that services their stuff, so spare parts should be on hand, or readily avaialble. I've dropped in the shop sporadically, going back decades, and he's always been a straight shooter, and reviews of him and his operation are excellent. We spoke on the phone the other day for 15 minutes, mostly about this reg service, and I'm pretty confident he's good-to-go.

 

[axxel57]

I'm guessing a lot of the info would apply to many regulators. I have people coming so I'll look at it later

Herman, do you happen to know if a kit is available for a Sherwood SRB 3100 first stage?

Not at Sherwood.......

 

[rsingler]

The D350 will pose a bit more of a challenge for you, right out of the box. My LDS' puncturing the diaphragm decades ago during disassembly was what got me started taking care of my gear myself.
Go through the SB threads for D-350 and D-400 as search terms and you'll see a host of posts on the subtleties of servicing this reg.
PM me if you decide you want to tackle this. As my avatar might suggest, it's my favorite reg ever, and the only center-balanced poppet around. No special tools needed beyond a pin wrench and a spoon. But lots of opportunities for misadventure, and spares are hard to come by.

 

[Mark IV]

Thanks bro, but i just left the newer MK10 first stage, and the older G250 2nd stage, with my LDS a couple hours ago, for the rebuild. After looking at both regs, that's what the owner suggested, which is what I was already thinking.
I may follow through later with servicing what is now "the other reg", (older,rattier MK10, and this newer D350). I guess i could use the D350 as the octo, but have a couple Sherwoods for that.

 

[rsingler]

I guess i could use the D350 as the octo, but have a couple Sherwoods for that.

NOT USE A D350 AS YOUR PRIMARY SECOND????
USE A SHERWOOD INSTEAD???

Oh my God. I think I'm going to have a heart attack.

 

[Mark IV]

LOL, read it again,bro ! I said I'd probably use a Sherwood as an octopus (only hypothetically suggested using the D350 as an octo)! The primary on this reg that;'s getting rebuilt now, is a G250. Ideally, I'd eventually hope to get the other MK10 rebuilt, and the D350 would stay the primary on that one.
(Whew! That was a close one!! )

 

[Fibonacci]

I have a Mk 5, MK 9 and MK 10 all stripped down and ready for rebuild, and while the VDH videos are really valuable they don't cover a couple of issues I have encountered.... help needed please!

Removing corrosion pitting... there is some pitting and annular grooves in the bore of one reg (through the plating) deeper than would be easily removed with 320/400/600/800/1200 wet and dry treatment. Can a fine grit brake cylinder flexhone be used lightly to remove pits or will the bore then be oversize for the piston and cause issues with o-ring extrusion or canting under pressure which then affects the HP seat?

Protecting honed bore...if the plating, pits and rings are honed out it would leave the bore as unprotected brass and I would assume prone to rapid corrosion in future despite the lubricant layer.
Birchwood Casey and EPI make a product that converts bright brass to a more stable black oxide layer.
Birchwood Casey Sporting Goods - Brass Black Touch-Up
Ultra-Blak 420 – Copper, Brass, and Bronze – Black Oxide – EPi
Use Ultra-Blak 420 to apply a deep black finish with excellent abrasion resistance to brass, bronze, copper, and copper-alloy surfaces.
Has anyone used this treatment before on SCUBA gear?

Environmental sealing... two regs have the small 1/16" or so SPEC ambient water ports which were supposed to hold in silicone grease in an early attempt at offering environmental sealing.
They are difficult to rinse out effectively (which is evident in the level of corrosion inside) so should they be repacked with Dow/Molycote 111 and if so what is the best procedure to ensure there are no voids?
For example Atomic Aquatics require the use of a special repacking tool to ensure the much lighter viscosity Christolube is distributed evenly.

 

[Couv]

Well, rats. I know someone who has a few MK5 NOS caps that would have solved your MK5 issues. He could have put them in a box heading your way just a couple of days ago. But I digress. The MK9 & 10 are a different matter because the piston head seal is in the body. But before we (you) do anything radical, have you confirmed that the pits/grooves are causing a problem? A leak in that area would manifest itself by blowing bubbles out the ambient chamber. If no bubbling under pressure exist then I would live with it. If you have bubbling, then your idea of using a cylinder hone followed by fine grit emery cloth might produce acceptable results. If I remember correctly, the last time I rebuilt a hydraulic clutch slave cylinder the stones were 400 grit-so they are available. If you abrade the cylinder uniformly, piston canting should not be an issue.

I agree that Dow Corning 111 is a better choice at this point as you might be wasting expensive Christo Lube/Tribo-lube/Krytox and even so-there's nothing wrong with Dow 111 for less than 40% O2 in the first place. It might not be as "good" a lubricant in the sense that PTFE grease reduces friction better than silicone grease, but the silicone based product has better "staying" power. The PIA regs I've rebuilt that had a proper job of packing with silicone grease were pristine on the inside.

How to pack? No air pockets in the grease is the key. I start with a peg in the body where the piston hole is so I don't push grease into it. Before installing the piston and spring, start packing the chamber-guesstimate to lessen the loss of grease but don't skimp. Then, install the spring (you did remember how many shims you removed right?) and pack some more. Last, remove the peg and install the piston (remember to use a bullet) and then screw on the pre-assembled cap/turret assembly. You should get grease oozing out of the ambient ports-and more when you pressurize. Recover the lost lubricant and put it into a plastic bag for later use as an o-ring "lube-o-matic" (thanks to Vance Harlow or was it Pete Wolfinger for that tip.)

Now, forget my drivel in the above paragraph. I just remember our very own @superstar made a MK10 packing video.


Please start with the MK 5. If successful carry on with the others. If no joy on the MK 5, don't tell anyone I said it was ok to use a (fine grit) hone and contact me so I can send a replacement cap. If successful-post pictures.

Couv

 

[Fibonacci]

Thanks Couv!
Aha... but you assumed it was the MK5 with the scoring when it was the MK9... I should have made it clear
The MK10 only has light marks that quickly came out.
OK will try the MK9 under pressure and see if it bubbles but I suspect the worst... plating corroded through.
Agree Dow 111 is particularly tenacious vs PTFE based lubricants.. really stays put!
An Atomic Z2 I pulled down over the weekend had a thin layer of atomised Christolube right through the second stage, the results of a heavy handed technician. Many o-rings were quite dry inside!
Thanks for the video link, makes it clear!
Will post some pics as I go...

 

[Couv]

D'oh.....I went back to re-read you post and your did say "one" reg. I thought all of the regs were pitted. Mea culpa.