I am having a problem getting all the air out of my brake lines on my 89 quadzilla. I am pumping up the brake lever until it has pressure then cracking the bleeder valve until the lever pulls all the way back. Before releasing the lever I tighten the bleeder valve. I have bled many brakes before and never had a problem. I have repeated this process and ran almost a complete can of brake fluid through the system. There are no more air bubbles coming out. Is it possible that there is air up in the master cylinder? The brakes work ok but they are still a bit spongy.

 

Sounds like one of the caliper sliders is rusted or corroded, and isnt sliding properly. The caliper needs to float, left and right to center up on the disk. Does the caliper move on the bracket, when its off the disk?
If youre getting pressure to the caliper, the master is bled.