BANDIT 600, put new pads on bike, bled the brakes, but after doing 60 miles they r still spongy. why is this?

I've got a 2001 Bandit 600, back brakes had been feeling spongy so decided to replace pads, done this and bled brakes, but after doing approx 60 miles brakes are no better. When you press the brake there is nothing. Can anyone tell me how to get them working?|||Air is in the system. This problem also happens on Hyd. disks brakes on Mtn bikes. After bleeding them again recheck the fluid level, all so make sure the reservoir stays full while bleeding them. Make sure when you re-tighten the bleed screw that you don't first release the brake lever allowing air back into the system.|||Still air in the lines.