Update: the technique from "Bike... and Dennis" of tying the brake lever to the throttle overnight worked. The brakes are firm even after sitting for a few hours.
As an avid SCUBA diver I was particularly pleased to read the wiki article an learn all my brakes needs was a decompression stop ;-)
Thanks for all the help. I will of course follow up on replacing the brake lines.
This is interesting, I read the Wikipedia page too, but have a question. Henry's Law states that the amount of dissolved gas in liquid is proportional to its partial pressure above the liquid. If I'm understanding this, air above the MC reservoir is one atmosphere and does not change with the MC piston compressed. What changes is the pressure of any air bubbles in the system. After all, with the MC piston compressed the check valve at the end of the piston is closed blocking the brake fluid from the atmosphere. Fluid does not compress, but any air bubbles would. In effect any air in the system will dissolve into the fluid in the system.
My last two bike builds have resulted in varying satisfaction with the brakes. On my CB450 the front is spongy and I have redone it twice. On the GL1200 the rear pedal is spongy, but the front came out nice. On the 1200 I used the plugged hole in the bottom of the caliper to reverse bleed. It pumped fluid up from the bottom and from the vary beginning it worked perfect. I have tried reverse bleeding, vacuum bleeding and old fashioned pumping the brakes.
I'm working on my GL1100 now and bleed the brakes last weeked. The front is OK, but could be better. The rear on the 1100 came out like the 1200 and is very disappointing. I will go down to the garage tonight and tie the front down on the 1100 and I will report back if it got any better.
I worked in a gas station when I was a kid and one of my jobs was to bleed brakes when the shop guys did a brake job. I will never forget the pressure bleeder they had. There was a plate that sealed to the top of the master cylinder and shop air would pressurize a tank that fed brake fluid under pressure to the brake system. Once the system was setup, all that was needed was to go to each slave cylinder and let off the fluid. There was never an issue with spongy brakes.
I putting together a similar system to use on my bikes. I have an older air conditioning flushing tool that I'm converting to a similar tool. I should have it ready to goo next week. I will report back.