kworkman
Master Diver
Posts: 336
Joined: Thu Aug 08, 2013 4:17 pm
First Name: Keith
Location: Columbus, OH

Scuba pro MK20

Sat Dec 09, 2017 12:25 pm

Anyone ever rebuild the MK20? I have a question about the piston sleeve. It has the 2 sleeves( one with a shoulder and one without) and an oring in the middle that you use the special tool to insert into the body. Are they suppose to lock in there tight or slide freely with the piston?

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rhwestfall
Master Diver
Posts: 493
Joined: Thu Jan 16, 2014 2:34 pm
First Name: Robert
Location: "La Grande Ile"

Re: Scuba pro MK20

Sun Dec 10, 2017 9:40 am

KW:

From my experiences of swapping out pistons on three of these (but not rebuilding at the time), the alignment bushings stayed in place while I pulled out and replaced the piston. I'd think it was more likely a slight "snug fit" than a "press fit"... or, lube held it, but I doubt that...

Frogkick.dk has the 20/25 Manual that IIRC, Pete had written. Think it is described in it, but it has been a while since I messed with my MK-20s or reviewed that document.
Bob

No Longer Awaiting my Kraken.....

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couv
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Posts: 347
Joined: Tue Jul 18, 2006 10:26 pm

Re: Scuba pro MK20

Sun Dec 10, 2017 2:11 pm

I've shied away from MK20/25 because you never know what piston or bushing assembly or who knows what you're going to find when you open it. However, in addition to the manual you may want to peruse the following bulletins which are available in Manuals and Catalogs on VDH:

MK 20 Super Glide Bushings
#267 Composite Piston (bushing installation is discussed)
MK 20 Piston and bushing installation
A sincere THANK YOU to all at VDH who make this wonderful resource available and to all the thoughtful contributors.

kworkman
Master Diver
Posts: 336
Joined: Thu Aug 08, 2013 4:17 pm
First Name: Keith
Location: Columbus, OH

Re: Scuba pro MK20

Sun Dec 10, 2017 11:30 pm

I will look at those. I did upgrade to the composite piston because I read that it was more reliable. maybe the spring that goes between the bushing and the seat holds the bushing

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