SP MK 10 PLUS: please help ID

[Zung]

Dear Board,

I've just got this reg off eBay, advertized as MK 10.

I opened the seat retainer and found a HP seat that looks a lot like that of the MK 20: black with a cylindrical "recess" in the middle.

Can anybody confirm this is actually a MK 10 PLUS? Does the "8" in the middle have any meaning?

Upon closer examination, the seat appears to be brand new, even thought the seat retainer is dirty. Is it likely that the former owner got it (a bit sloppily) serviced but never got it wet? The only comment I got from the seller is that it sat in a garage for 2 years.

Thanks for any comment.

Zung

 

[Fishpie]

A MK10 converted to a + will have a blunt piston (it may also have a cristolube filled plastic sheath around the piston), a white, black or green seat like the MK20/25. The seat carrier will also be of satin chrome. The kit also came with a 10+ sticker to put on the yoke knob.

 

[Zung]

Thanks Fishpie.

The seat retainer is actually satin with "Scubapro 300 bar" stamped, whereas the rest of the body is mirror (with a few scratches). So this is a converted MK 10.

 

[Zung]

The chrome on the "lower" part of the stem is gone, while the sealing edge appears to be OK with a loupe.

What I don't get is, according to the cutaways from the "Technical Service Reference & Repair Guide" by Peter Wolfinger, this part is not in contact with anything, and so has no reason to wear. The whole piston is held in place by the 2 o-rings plus the seat, right? Or is this the place where the sleeve, part #10-700-401 goes? There's no sleeve in the reg or in the guide, but it's provided in the maintenance kit and indicated in later schematics.

The guide also states that a "generous" amount of silicone should be applied between the piston and the bushing (the white part in the pic, TIB, #10-500-114). The problem is, the bushing doesn't want to come off when pulled gently. OK to apply some brute force?

Thanks for your help and advice.

 

[redacted]

that is not wear. That is the way it is produced.

 

[Zung]

I'm relieved, thanks.

 

[redacted]

I'm relieved, thanks.

I'm not that familiar with the mK10+ but the Mk20 had the same style piston when it first came out so it was easy to recognize. That style piston in the Mk20 had trouble with IP creep and has been upgraded. But the problem was manageable for DIYers as it simply required a good cleaning of the piston seating surface and a little christolube. I could usually go 6 months or more between cleanings but I did end up upgrading. I don't know if the Mk10+ has also been upgraded but I suspect it has been based on part numbers in old and new schematics.

 

[Couv]

Time for a downgrade...

 

[halocline]

I hope that MK10+ piston is WAY better than the brass-tipped Mk20 pistons, or else you're in for a real 'creepy' time!

As Couv suggested, you can always find a MK10 piston and seat retainer. The pistons come up on ebay from time to time. I've never seen a seat retainer, but someone's got to have one. I think it's the same main spring, so you'd just need those two parts.

 

[Zung]

Thanks for the scare, Gentlemen, in particular that "Creepy Time": I just love it.
Downgrading has actually crossed my mind, since I have 2 other Mk 10's, and the kit for the straight 10's come with 3 seats. Any one has a spare piston and a seat retainer? Pretty please?

For now, I'll patch it up, wait for warmer weather, do a few dives and report back to you guys.