Reassembling my SP MK2

[lhpdiver]

I've never seen it before (all my Mk2 stuff is older) but it looks like a thermal insulating bushing like they put on the Mk20/25 piston to reduce freeze ups. It probably also takes the place of at least 1 IP adjusting shim. I'd leave it off but save it unless you are diving cold stuff. This is one way scubapro implements upgrades.

Wait till you see all the extra parts you get in a Mk20/25 kit.

I will never dive in water too cold for my 3mm. Thanks!

 

[lhpdiver]

Newer Mk 2 pistons have a plastic guide that fits over the piston stem and inside the spring to keep the piston centered.

Well I'm assuming that that is the part I have pictured 2 posts up ??

My parts kits arrived (in like only 1 week from Singapore!) and I put my MK2 back together exactly as it was before I took it apart (using the same 3 shims). Hooked it up to my spiffy new IP gauge and got 130 at 3000 psi and a little less than 120 at 1500 psi. I was about to run around and see if any of the shops would sell me a new spring when I re-read your post.

When I put it on the piston stem and reassembled with the 3 shims I got an IP about 155 so I started backing out shims one at a time and now with no shims and only the mystery part I get 145 at 3000 psi and 135 at 1500 psi (I don't have any tanks with 300 psi at the moment).

Any comments ?

I regret that I wasn't more careful trying to get the yoke nut undone in the vise. I did scratch up the chrome in several places even though I wrapped it in a rag.

So now I need to pick up a torque wrench (probably on ebay) so I can set the yoke nut correctly. In the mean time I think I'll start servicing a R190 to go along with the MK2. Any words of advice ?

Thanks (you too awap) for all the help !

 

[redacted]

Any comments ?

I regret that I wasn't more careful trying to get the yoke nut undone in the vise. I did scratch up the chrome in several places even though I wrapped it in a rag.

The IP looks good - go with it.

I had a shop monkey take a bunch of chrome off my Mk2s. That and some high service prices was what got me started DIY. It's not pretty but it works just as well. I always feel better using a torque wrench. If you can find a 1/4 inch drive that covers 50 to 300 inch pounds you should have it all covered.

 

[DA Aquamaster]

I always have a first stage wrench in one of the LP or HP port when I take a reg apart in a padded vice. When placed against one of the jaws in when the reg is in the vice, the wrench will prevent the first stage body from turning. As long as the vice is also tight, you won't put enough strain on anything to break it.

In a pinch you can use an expended CO 2 cartridge in place of a first stage wrench, but the threads an most cartridges are not cut all that nicely and they spread the strain over a couple less threads in the first stage.

I'll second that a 145 IP at 3000 psi is perfect and 135 at 1500 psi is what you should be seeing.

The R190 is also easy to service, Just be careful when removing the metal poppet assembly not to put any strain on the plastic secind stage case as they can crack. If they have not been serviced in a while and/or if the threads were not lubricated, the poppet body and the nut can sometimes be a little hard to get apart.

You also want to use a multi-tool for this rather than trying to do it with pliers. Ideally you will have a multi-tool on the nut and a suitably sized open end wrench on the poppet body to take any strain off the case.

 

[redacted]

I always have a first stage wrench in one of the LP or HP port when I take a reg apart in a padded vice. When placed against one of the jaws in when the reg is in the vice, the wrench will prevent the first stage body from turning. As long as the vice is also tight, you won't put enough strain on anything to break it.

In a pinch you can use an expended CO 2 cartridge in place of a first stage wrench, but the threads an most cartridges are not cut all that nicely and they spread the strain over a couple less threads in the first stage.

I use an old LP or HP hose catching just the nut in the vice jaws with a rag or duct tape to around the body to prevent scratching. I then use a strap wrench around the Mk2 & vice so it doesn't slip out. Do you think that is an adequate substitute for the 1st stage wrench?

 

[lhpdiver]

You also want to use a multi-tool for this rather than trying to do it with pliers. Ideally you will have a multi-tool on the nut and a suitably sized open end wrench on the poppet body to take any strain off the case.

Hmmm - this r190 must be an old one. I can see using an open end wrench on the hex nut on the outside of the case (the "valve body") but I'm not clear what to use on the inside of the case. There is only the round, smooth "housing", the lever and the little nut.

 

[DA Aquamaster]

I'm sure it's a new one and I am sure you are correct - the end of the body is round. I had a brain fart this morning in my ruch to get to work and was thinking/referencing of some of the other similar second stages I have worked one. Generally, if there is a way to secure the poppet body from turning in the case, do it if things are sticking.

With an R190/380/390 if you have one that is stuck badly, you can remove the lever and poppet and then hold the body in place lightly with properly sized, shaped, and relatively large screwdriver. But be careful as it's cheaper to replace a cracked case than a damaged poppet body.

Soaking the case and poppet body, running hot water over it, and running it through the ultra sound cleaner for several minutes are other ways to loosen the salt or corrosion sticking the nut to the threaded part of the body.

 

[redacted]

Hmmm - this r190 must be an old one. I can see using an open end wrench on the hex nut on the outside of the case (the "valve body") but I'm not clear what to use on the inside of the case. There is only the round, smooth "housing", the lever and the little nut.

OK, now we are talking real opportunity to screw things up (voice of experience). I believe DA is talking about removing the hose from the R190. I use soft jaw pliers on that funny SP fitting that wants the special SP tool. Hold the nut by the case with a std wrench and remove the hose. To see what you are working with, remove the plug from the end fromthe end opposit the hose. It is a a round plug in a square hols so turn it about 1/8 turn until it will push out. Both end holes in the case are the same so you could swith them if you wanted the octo on your left. To avoid damaging the seat, I back off the orifice until I can blow thru the opening. This is actually the first opportunity to screw up. That plastic orifice can be hard to turn and sloppy screwdriver work or too much pressure can mess up the slot. If it doesn't turn pretty easily, soak it some more (days are a good idea). With the orifice backed off, the next thing to do is unscrew the demand valve body (big metal piece with the chrome nut). It is screwed into the housing which is squared off plastic, which you can see, over a round piece of brass with chromed threads (that are probably corroded to the valve body - more soaking). If you put much pressure on this, the brass part of the housing is going to turn breaking the plastic part. You should be able to hold the regulator easily in one hand and turn the nut with the other. If you think you have to get a better grip on the regulator, you are probably using too much force. When you do put too much force on it, you will hear a cracking and clicking sound which is the brass interior turning inside and cracking the plastic housing. Once enough of the plastic breaks away, you will be able to grip the brass piece and finish the disassembly - and start looking for a new housing (I hate learning from my mistakes).

I sometimes wish I practiced as much soaking as I preach.

Good luck

Edit: That round smooth housing that you see is square where it goes inside the case & that is what keeps it from turning. I don't think you can use a screwdriver to keep it from turning. If anything will help, it might be a pair of pliers holding across the smooth end that you can see may work. The brass underneath that plastic is serrated (not the right work) and grips the plastic so it can't twist.

 

[lhpdiver]

soaking

 

[redacted]

Edit: That round smooth housing that you see is square where it goes inside the case & that is what keeps it from turning. I don't think you can use a screwdriver to keep it from turning. If anything will help, it might be a pair of pliers holding across the smooth end that you can see may work. The brass underneath that plastic is serrated (not the right work) and grips the plastic so it can't twist.

Knurled was the word I was looking for. The housing is a capped brass cylinder, withy the brass cap on the lever (inside end). That cylinder is knurled under the plastic on the inside end that you can see and the plastic is molded into and engages that knurling. The opening in the case that the housing extends into is square so the plastic which is molded over the smooth brass cylinder in that area is square and keeps the whole thing from turning once assembled. But that square area of the plastic will crack and break under too much pressure. That is the problem with holding the case as you try to turn the valve body. On the back side of the housing are two holes which send the air into the reg towards the mouthpiece when you inhale. Those hole go thru the plastic & brass and could probablu be used to stabilize the housing if you can get to them. I don't think you can. If all else fails, I'd try to stabilize the the visible end of the housing with pliers as you turn the demand valve nut. This would keep the pressure off the thinner, squared off area of the housing that won't take it. If soaking loosens it up, it should come off with about the same torque as is used on the hose nut. This much torque should not damage the housing. Also as you try to work that connection, try both tightening and loosening (both directions). That should help break the deposits that are holding it from freely turning.

Good luck.