DIY reg servicing

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awap

Do you have the equivalent standard O-ring numbers for the Mk-5?

Thanks

Sure do. It's similar to the Mk 10 with a few exceptions. The piston o-ring is a 2-022 which is the same as a Mk20. The turret swivel o-ring is a 2-012. The yoke nut uses a 2-015 which is the same as a Mk2. And there is no o-ring required between the ambient chamber and the body.

I worked these out myself based on schematics and full-sized drawings. And I'm fairly sure that I have confirmed each of these sizings while servicing my regs. But if anything doesn't seem right, lets double check. I did find an error in the scubapro o-ring chart for my Mk7 but the error was quite obvious when I did the first service.

 

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Please do your self a favor and DO NOT USE dental picks......
ONLY use brass picks as a stainless metal pick can and will scratch the chrome in an O-ring groove (seen it done many many times) in the case of the piston shaft O-ring it can cause bubbles to come out the Amb.ports.

As to the reusing the cave hp seat, if you remove the hp seat/cap away from the piston in the mk10/mk5 style (sharp edge piston), and then replace. You can cause IP creep due to the knife edge not meeting up with the old groove.

Yeah, those dental picks are pretty hard and sharp. I've tried brass picks but didn't care for them either. I have the scubatools pick set and do most of the work with the 90 degree fish hook shaped pick.

And that is a good point on the HP seat. I don't remove the HP seat from the seat retainer unless I plan to replace it. Stuff isn't perfectly centered so if you move the seat, the piston will have to cut a new grove which will cross any that are already there. It will adversly effect pereformance and eventually lead to IP creap problems. I've never tried marking it so it can be reinstalled in the same orientation but that is probably unnecessary anyway. Just clean it up as best you can with the seat installed in the seat retainer.

 

[Packhorse]

How much silicon should I be using on the Orings? Should I only use crystal lube or is regular silicon OK for non O2 clean gear.

As far as O2 clean goes, can I still get away with the standard Orings and seats and use crystal lube or do I need to use Vitron or EPDM.

Thanks guys your replys are priceless.

 

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I only use christolube. I believe it is recognized to be a better lube and protectant than silicon. In most cased, rub in just enough to give the o-ring a sheen. Exceptions are douible o-rings like the 2 on the Mk25 piston or the balanced poppet. I load up the space between the 2 rings as much as I can. Also the HP piston o-ring on the Mk5/10. They will produce a shrill squealing noise if they are not well lubed.

 

[dryan]

hi all,i just got a service (repair kit)for my mk20. i purchased the reg s500 mk20 new back in 1999 while on a ski trip to andorra.i have almost 300 dives on it and never had it serviced and still works perfect.but dosent have that new feel to it anymore.so i decided to service it my self. the problem im having is the two white plastic piston rings that go on either side of the main rubber o ring on the piston head have chaffered edge on one side.does anyone know what way these plastic rings face with chaffered edge or does it really matter what way they face.any help would be greatful,thanx.

 

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hi all,i just got a service (repair kit)for my mk20. i purchased the reg s500 mk20 new back in 1999 while on a ski trip to andorra.i have almost 300 dives on it and never had it serviced and still works perfect.but dosent have that new feel to it anymore.so i decided to service it my self. the problem im having is the two white plastic piston rings that go on either side of the main rubber o ring on the piston head have chaffered edge on one side.does anyone know what way these plastic rings face with chaffered edge or does it really matter what way they face.any help would be greatful,thanx.

Yes, it does matter. Your post may be a bit confusing as newer kits have black bushings rather than white bushings, if we are talking the same thing. Two bushing (about 10mm outer diameter) that fit on the piston shaft on either side of the HP o-ring. One of the bushings has a shoulder and it goes into the body last and with the shoulder end in contact with the spring and the rounded end in contact with the HP o-ring. The other one goes in first with the squared end into the body and the rounded end again in contact with the o-ring. So, shoulder bushing last with the rounded edns of each bushing in contact with the HP o-ring.

If. OTOH, you are talking about the 28mm plastic ring that serves as a backup ring for the piston head LP o-ring, then only one ring is used. It goes on the ambient pressure side of the o-ring only on older style pistons (1999 would be older style) and I don't believe there is any difference one side to the other (at least I can't see any). If you have an older style piston with a brass tip, they tend to have some IP creep problems due to imperfections developing in the brass tip. My Mk20 with that style piston required fairly regular (6 months) cleanings to keep IP under control.

 

[dryan]

thank you for the reply,but i think we are on about two different things. im talking about the white plastic split rings that go on the piston crown or head.there is one on either side of the main piston rubber o ring.they look like scrapers (in mechanical terms) these rings are not identicall on their sides.there is a slight chaffer on them. id just like to know do the chaffer side face the piston crown or the piston neck or the rubber o ring on the piston head groove.

 

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thank you for the reply,but i think we are on about two different things. im talking about the white plastic split rings that go on the piston crown or head.there is one on either side of the main piston rubber o ring.they look like scrapers (in mechanical terms) these rings are not identicall on their sides.there is a slight chaffer on them. id just like to know do the chaffer side face the piston crown or the piston neck or the rubber o ring on the piston head groove.

That is the large backup ring. You should only use 1 on the ambient side of the piston head o-ring. I find nothing in the repair guide about one side being different from the other. Although, if you are reusing a ring, there might have been some wear making it look different. A new ring looks to be perfectly square in its cross section.

 

[dryan]

so its called the back up ring. there is definitly 2 of them rings on the piston crown.my reg was never opened before,and when i did open it a few days ago (2 back up rings) 1 on either side of the main rubber o ring.the service kit had 2 of them back up rings in it so i just done a straight swap.And as far as the rings having the same dimension on both sides i dont think so. on very close inspection there is def a difference,but i guess it dosent really matter which way they go on then. i haved dived with it since and it seems ok, but just wanted to make sure, thanks again.

 

[Zung]

You have the 3rd generation stainless steel piston with 2 anti-extrusion (or backup) rings; they came just before the current "composite" piston. I can't find any formal reference for the positioning, and I don't know what you mean by "chaffer" (chamfer). If it's a contour, it should face the o-ring, like in here; if it's just an angle, I don't think it matters much, I'd put the angle away from the o-ring. The current piston doesn't use any backup ring.