Track day looming and an unforseen problem has arisen. Took the bike around the block to make sure everything works OK, first 3 corner fine. Last corner, front brakes stay on, lever rock hard. OK so I get a spanner and release the bleeder nipple on the brake lever and brakes release OK. So I drain brake fluid, as this was one thing I was yet to do anyway, fill up the reservoir with nice new fluid and commence bleeding. Now, lever is feather light and does not seem to be pumping any fluid down to the calipers. So I can't bleed the brakes as there is NO pressure. Pulled the master cylinder apart and all semms OK, lines are all OK, caliper pistons are moving in and out. However, when I push the pistons back, instead of pushing fluid back up to the reservoir, they only push against the other caliper, and none to the reservoir? I don't know what is wrong or if I am doing something wrong? Any suggestion people of great knowledge?