What Ed said. I put a new Super Beetle M/C on my Spyder last year and the first time I did it, I didn't bench bleed it. It took me the better part of two afternoons to get decent pedal.
I had to pull it and reinstall it and the second time it took about ten minutes after bench bleeding it prior to install.
But i think Alan hit the nail on the head. You need a higher capacity M/C to push the pistons in disc brakes.
PS: My son the motorcycle mechanic helped me bleed my brakes both times. He taught me a little trick: tapping on the M/C between pumps. I guess it helps break loose little air bubbles that are clinging to the sides of the bore.