Scubapro MK21 seat (same as MK25 seat) - metal spacer doesn't want to press into seat

[aoumi]

Just finished overhauling my MK21, all went smoothly with 1 exception. I understand the MK25 and MK21 seat and seat retainer configuration are the same.

What happened, is that the plastic seat (part no 10.101.161), has sitting on top of it a metal 'spacer' with a dimple on it (part no 10.752.102). The dimple simply fits into the back of the plastic seat, there is a hole on the seat to receive it.

However, when I installed the new seat, the spacer didn't seem to just sit on top of the seat, the dimple wouldn't insert into the seat. (The old one just sat on top, no force required to install it, and fell out on its own when dis-assembling).

I tried pushing the spacer with dimple into the seat, but it didn't seem to want to fit, or perhaps it actually WAS sitting flat on the seat - it was hard to tell with it installed in reg body, so I continued with assembly.

When it came to to adjust the IP (after reassembly was completed), the adjustment screw, during installation, was installed backed all the way out, so needed screwing in before the the regulator is able to hold an acceptable IP. So I started screwing it in with the allen key while the reg was de-pressurised. It screwed in a bit, then met some resistance.

So, I turned on the air very slowly (with IP gauge and 2nd stage attached), and the reg was going over 150 psi even though resistance had been met with the screw. So, I again de-pressurised it, and slowly screwed in some more - this time against the resistance. The resistance held for maybe 1/3 of a turn of the screw, then reduced back to nothing at all. After this, turned on the air again, and this time the reg held an IP closer to acceptable, on the high side, but I was able to de-pressurize it again and screw in the adjustment screw more (a little each time before checking the IP), and eventually set a stable 135 IP. It locks up ok, and doesn't creep.

My assumption is, that I had to turn the adjustment screw in, in order to press the dimple of the spacer into the seat. Is this normal? Or was there a bad batch of seats that were manufactured a while back with the incorrect size hole to receive the dimple? Maybe this is perfectly normal, but wanted to see what the experts here say. It seems to be not what I would have expected.

Here is a picture during dis-assembly of seat:


and the spacer:

 

[northernone]

Hmmm. Here's a similar experience report.

I've seen that seat and spacer be a tight fit. Don't know if it's poor manufacturing tolerances or the service kit... Regardless, held IP fine after pressing it into place. Anyone else?

Cameron

 

[aoumi]

No thoughts on this anyone? I'm guessing perhaps very common hence no comments...

My first thought is perhaps a batch of out-of-spec seats (dimple not fitting), also suspiciously, the service kit I purchased 'new', it had been opened before and carefully re-stapled - but the original staple holes were still there. I suspect it was a few years old as well.

The IP is stable and locks up fine, I guess in the worse case, it's try find a new seat and washer for the IP adjustment retainer somewhere.... however not easy to come by without buying an entire service kit.

 

[rsingler]

Very common.
You did the right thing by screwing it in sequentially. The spacer just needed to spread the dimple a little to drop fully into place. Very common that it just falls out. I usually put a touch of the yellow gold heavy PTFE grease that's specified for the adjustment screw, on the back of the spacer to help it stick.
Only thing I'd recommend is starting with the adjustment screw in some more, so that your IP doesn't start high. Then back it out a little at a time to raise IP, rather than in to lower IP.

 

[aoumi]

Thanks for that, seems it wasn't unique to me. Also, next time I will start off with the screw adjusted in more, makes much more sense to start with a low IP and adjust higher, rather than high aiming for lower.