I will have to search for that post as I am definately not up to speed on these pumps. I gather they passed air to the atmosphere readily? Weird.
I have never heard of Otto rings. I went via The Greek. I am hoping they work out.
Those Greek rings are only 0.059" or 1.5mm metric nominal thickness, what was your side gap clearance in the piston ring lands? 0.005" is the limit, .003" is standard
I sent three pair of those Caber rings back to Athens, but other members have used them. Dimitris doesn't mention that fact in the description.
Correct, the oiler diaphragm first, then the gasket. It helps hold it down if you haven't added the bridge yet. If you look at the various IPLs for that saw series, you'll see it assembled both ways.
Cap Mod
http://www.arboristsite.com/community/threads/poulan-s25-oiler-fix.273837/#post-5228804
Otto
http://www.arboristsite.com/community/threads/poulan-thread.98495/page-1628#post-5037865