That's exactly the same problem I had with my OE master cylinder on the SP2: it felt spongy from the moment I picked up the bike from my mate in Rome and no amount of bleeding or tinkering (including changing two brake levers) could solve the problem. I was about to take it apart to fully service it when I saw a nice Brembo radial master cylinder with a nice rebate at a local store and that settled the matter...
