Mk5 Questions

[LeadTurn_SD]

I was so curious about the shims (that I knew we not there) that I zipped home at lunch at looked again, more carefully this time.....

Well....... Hat's-off to the Masters (awap & halocline). Color me embarassed, there are three sneaky, ninja, stealth shims quietly hiding up in the end of the body, waiting for a Mk5 "virgin" like me to wander along :shocked2:

They are paper thin, nearly-transparent, and I looked right at them and didn't see them the first time

Is it about 5psi per shim? If that is the case, removing them would put the IP at 135... could be worth a try...

halocline, thanks for the offer! I'm still deciding how I want to proceed, but think I'm going to just throw a rebuild kit in this first time, since it looks like the kits come with a few seats (of various heights?).... but after that, I may just use generic o-rings based on couv's nice annotated diagram.... but if I get stuck I'll let you guys know.

zung, this is my first Scubapro piston (I've dove them, just never worked on them), and my 2nd R109. The R109 that came with this Mk5 is in near-new condition, but has been upgraded with new (blue) diaphragm, new exhaust valve, and converted to BA with the S-wing poppet. It is "ready to dive" as is, but I tore it apart anyway to see what was inside and will just clean, lube and tune.

Thanks again for the advice gentlemen.

I'll update this when I do some more work on it.

Best wishes.

 

[Zung]

You don't need a service kit for now if you have 1 each:

• -010 (pos. 8) & -013 (pos. 4) in Duro 90
• -012 (pos. 16) & -022 (pos. 12) in Duro 70

Flip the seat over, cook the air filter real good in the ultrasonic, and you're there.

 

[redacted]

You don't need a service kit for now if you have 1 each:

• -010 (pos. 8) & -013 (pos. 4) in Duro 90
• -012 (pos. 16) & -022 (pos. 12) in Duro 70

Flip the seat over, cook the air filter real good in the ultrasonic, and you're there.

With IP locking up at 150, I'd just remove the shims and leave the seat alone for an IP of 135. The fact that it was serviced this century and still has the flat seat suggests to me that the seat was already flipped in the last service. I would replace those two dynamic o-rings while it is opened if you have them, especially that 010. It is such a job removing and installing that one that it is pretty much a must replace in my book. The piston head o-ring, OTOH, is easy enough to get to that it could wait until it starts to leak. I might still have some blue ones in service.

 

[Zung]

Yeah, LT, do tell us your experience with that 010, especially if you have the whitish (PU) one, but please remove all the rated "R" words.

It's my worst nightmare and the reason why I'd rather have the MK20.

Edit:

Has anyone attempted to simulate the Scubatools tool by glueing some kind of a ring around a suitably thin pen or a suitably thick chopstick? It's for plugging the bottom of the body up to where the o-ring groove is.

 

[redacted]

Yeah, LT, do tell us your experience with that 010, especially if you have the whitish (PU) one, but please remove all the rated "R" words.

It's my worst nightmare and the reason why I'd rather have the MK20.

You need more practice.

Use a double hook pick and slip it down one side of the o-ring and then turn it to hook the o-ring and pull it out. I bent the hook on mine just a bit so it sits at about 85 degrees rather than 90 degrees making it easier to hook that o-ring.

Instal is a bit more fun. You could always take the easy way out and buy the special tool. Not my style. I lube the O-ring, twist it into a figure 8. and stick it into a short piece of a plastic straw. Then I use the faithful double hook pick to push it out of the straw and into the body. Still with the double hook pick, position the o-ring in the area of the groove and use the pick to push a segment of the o-ring into the groove. I then use a dowel from one end to prevent the o-ring from slipping by the groove and the rounded part of the double hook from the other end to work the o-ring into the groove. You may have to talk to it a bit but it will work. Then I use a plastic tooth pick to gob it up with Tribolube with a little added to the bullet tool and piston stem; and insert the piston, almost always remembering to install the spring first.

 

[halocline]

Flip the seat over, cook the air filter real good in the ultrasonic, and you're there.

The new conical seats are much better, don't use the old flat one. I suspect the IP will change dramatically with the new seat, so I'd start by taking the shims out and try the middle height seat just to see where you are.

Regarding getting the old HP o-ring out and the new one in, the double hook pick that awap suggests is terrific. I just pierce the old one, which has the advantage of burying the point of the pick, and twist it out. I grab the new one with some tweezers, insert one end into the chamber, and work it in place using wooden chopsticks from both sides. It's really no big deal; the 90 duro polyurethane o-rings put up a bit of a struggle, but that's life.

Awap taught me the straw trick, but I'd forgotten about it. Next time I'll try that again. I'm sure it works great.

It's a good idea to spend some time on the piston removing any glaze from the shaft where the o-ring goes. You want to minimize friction at that point.

 

[Zung]

... I then use a dowel from one end to prevent the o-ring from slipping by the groove...

The magic word is "dowel". I figure with a step to it, an inner diameter that fits the hole, and an outer diameter that prevents it from going further than .1" (MK10) or .415" (MK5), my life would be a lot less miserable. But wait, that's part #20-275-400, Mark 5 / Mark 10 O'ring Tool Kit!

 

[redacted]

The magic word is "dowel". I figure with a step to it, an inner diameter that fits the hole, and an outer diameter that prevents it from going further than .1" (MK10) or .415" (MK5), my life would be a lot less miserable. But wait, that's part #20-275-400, Mark 5 / Mark 10 O'ring Tool Kit!

I use the same dowel on both my Mk5/7s and my Mk10s - just hold it in the right place. I thought about getting fancy, but why?

 

[LeadTurn_SD]

Thanks for all the advice gents!

A stomach flu flattened me today, so diving and/or Mk5 experimentation were put on hold :depressed:

I am going to remove all the red paint from the Mk5's spring since I found tiny bits of paint on the knife edge of the piston, and get queasy at the thought of breathing that in....

While I wait for the Mk5 rebuild kit, I'll probably, just for fun, try a classic "underhaul" first: cleaning and relubing, leave the seat undisturbed, and retest IP with the all 3 shims in and all the "old" o-rings. I expect the IP may still be too high, and if so, then remove a shim or three

I'll use due caution with the piston o-ring. And thanks again for all of the tips!

Best wishes.

 

[Zung]

... I'll use due caution with the piston o-ring...Best wishes.

Use a piston bullet or ask couv about his drinking straw magic.