MR12 Rebuild Issue?

[Nick_R]

Here is a photo I have taken of the bore inside an MR12DFC 1st stage, I have circled the trouble spots in the photo, what I'm wondering is if this is common, it looks to me that they are wear marks from the HP Chamber, its kinda hard to take photos down inside that bore, did the best I could....Also this one has no poppet seat, just the valve which is listed as part number 9 on exploded view, part number 75 which is the 1st stage poppet seat is not on this drawing, just the MR12 LONG....Im not a tech, just trying my hand at figuring out how things work and rebuild my own 1st stage

 

[Fishpie]

Don't worry about the sides....it's the volcano in the middle that makes the seal with the seat....and that looks fine from here.
btw if you have problems sourcing Mares parts (for your own personal reg) the blue AquaLung seat and balance chamber o ring will work fine in place of the Mares parts.

 

[Nick_R]

I havent seen a new one apart, so to me as a machinist seeing something like that stands out like a sore thumb...Im also wondering why one drawing lists the poppet seat but the other dont, this one didnt have the poppet seat in there, just the valve.

was the poppet seat added in later to the same design as an extra means of safety?

 

[Fishpie]

Here's what should be in that part of the 1st stage (in order going down).
Circlip
Sintered filter
Balance chamber (with small o ring and teflon washer inside)
Spring
HP Seat
Pin

 

[Nick_R]

here are the 2 exploded views in question about the valve and poppet seat variances, one shows it the other doesnt???

 

[Fishpie]

Some MR12's had a removable volcano (parts 74 and 75).....yours doesn't.

 

[Nick_R]

so my version I cannot replace the seat, just the valve?

 

[Nick_R]

looks to me like a teflon coating on top of the valve(9)

9 46185002 MR 12 first stage valve

it looks fine as does the seat surface on the 1st stage body for the version with the replaceable seat the drawing lists a different valve(9)

9 46200276 Pebax 1st Stage poppet

would this be a better replacement? although I think the one thats in it looks good with hardly any marks on the seat surface

 

[Fishpie]

The parts to replace are HP Seat#9 and o ring #2.
The circlip #2 and sintered filter #22 should be inspected and (usually) replaced.

 

[Nick_R]

9 is listed as not coming in the annual service kit, so has to be bought seperate all the rest are showing in the kit, except for the diaphram and no more than what that costs might as well replace it too