SP MK 10 plus - Help Please

[wwunder]

I recently picked up a mk10 plus with a d400 second stage on a trade and knew that the ip was a little high when I got it. I assumed that it just needed a decent service, but after picking up a service kit and installing a new hp seat the ip is still way too high.

It appears to try to lock up at about 130 psi, but creeps quite quickly (10 seconds) to 175 psi at which time the second stage starts bleeding off or I purge it. I can't detect any knicks or anything on the piston tip, but have only checked with my fingernail, not with magnification yet.

Does anyone have any tips on how to get it to lock up? I don't have too much budget left for fiddling with the reg, in fact i would rather back - convert it to a mk 10 to match another couple I have. Failing repair are the parts worth anything? I believe some people like the 3000 psi yoke for their earlier production ones and how about the 5 port turret?

 

[DA Aquamaster]

It sounde like it needsa new piston. I should have one sitting around some where for either a Mk 10 Plus or more likely a MK 10. Send me a Pm and I'll see what I can find

 

[Couv]

While the piston may very well be suspect, before you purchase a new one, make sure the piston stem o-ring is a duro 90. The o-ring could be extruding causing the piston to drag. Of course, make sure both the piston stem and the o-ring are properly lubricated. If still no joy, check the hp seat again to make sure it's ok and is not cross engraved.

To convert it to a regular MK10, you'll need a piston, hp seat, and seat retainer.

Couv

 

[wwunder]

Interesting, I hadn't considered that. I did try it in another Mk10 body and it behaved the same (without) changing the stem oring in either. I guess it can't hurt to try. I assume that the oring supplied in the annual kit would be the correct 90 duro???

 

[BlueWaterDiving]

Yes it will have a red line on it. Use a bullet to put the piston back in. If you do not use a bullet you will cut the o-ring.

 

[Couv]

Right, the kit should have the correct o-ring, but from reading your first post, I was not sure you had installed it. If you do not have a bullet, you can take a plastic drinking straw (a trip to Whataburger for a malt may be called for) and slip it over the piston stem. Once you have pushed the stem and straw past the o-ring, pull the straw out from the other side. If you did the fingernail test on the piston and did not feel any imperfection, it is probably ok, but if not, you may as well try to dress it out with some emery paper or crocus cloth.

If you have not done so, do not remove the seat from the seat retainer unless you index mark it carefully so it will go back in the exact same position.

Good luck,

Couv