halocline
Contributor
Do you have access to a micrometer? If you could measure the height and diameter of that seat, that would be great. I have a MK15 spring I'll trade you for a few of those seats if they are the right size. I'll throw in a handful of bushings as well.
The D400 is a great 2nd stage, maybe one of the best ever. You happened to pick two of the most difficult 1st-2nd stages to DIY in the SP line-up, BTW. When it's in the up (predive) position, the dive/predive switch activates a spring which rests against the lever. This keeps the reg from free-flowing. When its in the down (dive) position, it moves the spring away from the lever and has no affect on the operation of the reg. It should have zero affect on the purge in either position. BEFORE YOU TAKE ANYTHING APART, take lots of photos of the lever and spring orientation. Just pull the rubber cover off, unscrew the ring, and gently take the diaphragm out and off the lever. Getting that spring off the cross-barrel and getting the lever oriented correctly is not something you're likely to remember, at least if you're anything like me. Since you have a few D400s (right?) you can photograph each of them to make sure they're all the same. The schematic does NOT clearly show the orientation of these parts IMO.
Get the Harlow book. There's another one too, called regulator savvy, by Peter Wolfinger. That book is not so much a manual for DIY, but it does have extensive and detailed explanations about how various regulators work. Included is a whole chapter on the D series, so consider that one as well, if you will be working on these regs. While the basic principles between the D series co-axial valve and standard barrel poppet 2nds are the same, the application of those principles is quite a bit different, and the D series is engineered to solve some basic problems in a very elegant and sophisticated way.
None of us would be recommending these books if we didn't think they were worth it. What do you think, we get paid for doing this?
The D400 is a great 2nd stage, maybe one of the best ever. You happened to pick two of the most difficult 1st-2nd stages to DIY in the SP line-up, BTW. When it's in the up (predive) position, the dive/predive switch activates a spring which rests against the lever. This keeps the reg from free-flowing. When its in the down (dive) position, it moves the spring away from the lever and has no affect on the operation of the reg. It should have zero affect on the purge in either position. BEFORE YOU TAKE ANYTHING APART, take lots of photos of the lever and spring orientation. Just pull the rubber cover off, unscrew the ring, and gently take the diaphragm out and off the lever. Getting that spring off the cross-barrel and getting the lever oriented correctly is not something you're likely to remember, at least if you're anything like me. Since you have a few D400s (right?) you can photograph each of them to make sure they're all the same. The schematic does NOT clearly show the orientation of these parts IMO.
Get the Harlow book. There's another one too, called regulator savvy, by Peter Wolfinger. That book is not so much a manual for DIY, but it does have extensive and detailed explanations about how various regulators work. Included is a whole chapter on the D series, so consider that one as well, if you will be working on these regs. While the basic principles between the D series co-axial valve and standard barrel poppet 2nds are the same, the application of those principles is quite a bit different, and the D series is engineered to solve some basic problems in a very elegant and sophisticated way.
None of us would be recommending these books if we didn't think they were worth it. What do you think, we get paid for doing this?
