followed this video when during bleeds of my stokers. How old is the bike/brake set? You might try rebuilding the calipers, new seals and pistons. One thing I do with my stokers is after a good bleed is cap off the reservoir and then squeeze a bit more fluid in to the system still i get the lever feel that i want then close the bleed valve while still squeezing the bottle. Works like a charm.

Stroker bleeding procedure - YouTube


Found this one for the nines,

http://youtu.be/qfycdRfT8RQ