1st time overhauling my MK25 - could use some help, please

[divedrewsf]

Hello - I have been diving Scubapro MK11 + G250 for the past many years and servicing both with ease every year. I bought a MK25/G260 last year and just did the first service on it. Not sure if it's familiarity or what, but I'm having a tough time with this piston reg.

I'm able to get IP to stick at 130 (after it creeps up slowly after a purge). I do not hear any leaks and it breathes fine with the G260 tuned to proper cracking pressure.

My problem - when I close the tank, it slowly bleeds out. Right after the tank is closed is 'quickest' but then it bleeds out very very slowly once the SPG moves to about 1000psi. My MK11s (diaphragm) hold firm once the tank closes. Is this bleed just inherent to piston regs? Is it actually a leak (and if so, where do you suggest I look first...seems the HP seat is fine, given it's holding IP). One thing I remember is there were two plastic shims when I took it apart...and my kit only had one so I just put one back in thinking that is what I was supposed to do. Should I add another shim? How would that change things (IP)?

Anyway, any and all feedback greatly appreciated! Thank you.

 

[Angelo Farina]

Hello - I have been diving Scubapro MK11 + G250 for the past many years and servicing both with ease every year. I bought a MK25/G260 last year and just did the first service on it. Not sure if it's familiarity or what, but I'm having a tough time with this piston reg.

I'm able to get IP to stick at 130 (after it creeps up slowly after a purge). I do not hear any leaks and it breathes fine with the G260 tuned to proper cracking pressure.

My problem - when I close the tank, it slowly bleeds out. Right after the tank is closed is 'quickest' but then it bleeds out very very slowly once the SPG moves to about 1000psi. My MK11s (diaphragm) hold firm once the tank closes. Is this bleed just inherent to piston regs? Is it actually a leak (and if so, where do you suggest I look first...seems the HP seat is fine, given it's holding IP). One thing I remember is there were two plastic shims when I took it apart...and my kit only had one so I just put one back in thinking that is what I was supposed to do. Should I add another shim? How would that change things (IP)?

Anyway, any and all feedback greatly appreciated! Thank you.

It should not bleed with the valve closed. Where is the air going?
Do you see bubbles while keeping it submerged?
If the reg originally had two shims, possibly you should have also now. But the lack of one shim simply causes the reg to lock at a smaller IP. This cannot be the cause of bleeding...

 

[rhwestfall]

I imagine that if you put it in water, you would see bubbles escaping from the ambient chamber. I'd start with it being a bad piston head o-ring or not lubed properly.

Water is your friend...

 

[lexvil]

Shouldn’t do that, you’ll need to find where it’s coming from.

 

[Open Ocean Diver]

Ip is adjustable on the MK25 with an outside adjustment screw. No sense in adjusting the IP until you find the leak. You need to dunk it in water, fill up the bathtub or if you have a pool that’s a great place to do it too.

 

[divedrewsf]

hi all....thank you for your comments!

good news/bad news. good news is there are NO leaks from the 1st stage....that appears all tight. But, the bad news is that I have a G250 as my octo and that *was* leaking. and when I try to adjust the cracking point on it, I just can't get it to work at all now. I did not overhaul this when I did the MK25 + G260. Maybe that's the issue?

but....I took a R295 from another rig and it took care of the issue. IP holding firm at 130 and no leaks when the tank is shut off!

so, maybe this combo - MK25 + G260 - just doesn't 'like' the G250 as the octo? I'll tinker more and see (hook up this G250 to the other rig I took the R295 from)

again, thank you!

 

[rhwestfall]

so, maybe this combo - MK25 + G260 - just doesn't 'like' the G250 as the octo?

Ummmm no....

 

[rhwestfall]

Did you cut the seat on the G250 adjusting it? Did you replace the second stage poppet seat, or are you re-using it? Are you sure you have the lever/feet in the correct orientation or together correctly?

 

[divedrewsf]

the g250 and g260 tune exactly the same mate.

it's the g250. i put it on the other rig and it continues to act up. i'll overhaul that one now. sure that will cure this.

but the good news is the MK25 + G260 + R295 is all good to go. so my OP is handled. thanks all!

/thread

 

[rhwestfall]

the g250 and g260 tune exactly the same mate.

Nope... G260 has a micro-adjust on the balance chamber side so you tune orifice to set lever height, and micro-adjust to set cracking effort...