Scubapro MK 20 creeping badly

[snowdog61]

If I remember right, the mold injection marks should be AWAY from the O-Ring. correct?

don't think they are injection marks but yes, they go away from the o-ring. If you look closely at the parts stack, it shows. Shoulder for the top support of course goes away from the o-ring too.

 

[J_Rod]

Update....

Own 3 MK20's and 4 MK25's....thought it wise to get all the recommended materials/tools for servicing this model, just to make it as easy/reliable as possible, so it took a bit. Didn't realize how simple the MK20/25 was...in a half hour, I upgraded a brass tipped MK20 piston to a composite MK25 piston, and serviced. IP cycle went from 100# to 145 but creeping to 160#, to 110 locking at 120 within 3 seconds and was stable for a half hour. I stopped watching at that point. I have 2 shims in. Is this IP within specs? I read should be 120 to 145..I only purge cycled about 20 times.

 

[redacted]

Spec is 125+ but I don't think you will have any problem. At least use it a bit more before you go through the trouble of changing it.

 

[guruboy]

I think they teach 145psi IP at 500psi tank.

 

[buddhasummer]

I think they teach 145psi IP at 500psi tank.

Only for their diaphragm regs. My understanding is If you set a piston reg at 145 at low tank pressure you're likely to be out of spec (above high) at full tank. My MK10s seem to swing 5-10 PSI. If I set at 145 at 500psi ip will be at around 155 at 3000psi. So you'd set ip at 3000psi.

 

[halocline]

I aim for 130-135 on mine, but they're often a bit lower. You might try adding another shim under the seat retainer or just see how it performs at 120. Depending on the 2nd stage you might not notice much difference.

 

[J_Rod]

[QUOTE="halocline, post: 7988371, member: Depending on the 2nd stage you might not notice much difference.[/QUOTE]

Pairing it with an S600. I will add a shim if I notice diminished performance. I have a pneumatic adjustment tool, so I suppose I can adjust the 2nd too. My understanding is, that as it breaks in/wears I can expect an increased IP anyway. Correct?

 

[buddhasummer]

Correct.

 

[halocline]

My understanding is, that as it breaks in/wears I can expect an increased IP anyway. Correct?

I think once it initially breaks in the resting IP can go down a little, but as is wears over the long term it will go up.

 

[J_Rod]

I'll do a few <60' dives and see how the pair performs. I suppose I can upgrade to the non-shimmed adjustable IP, if necessary. I really enjoy the opportunity to do these things. Thank you all for being a database of knowledge for those willing to learn!