During the long inactive period, the master cylinder was disconnected from the handlebar and left hanging upside down about the level of the calipers. I am guessing that the air in the top of the master has worked its way into the brake lines. I rebuilt the master 2 years ago and the calipers 3 years ago, so I don't suspect anything wrong there.
I have a MityVac and I think I can use it to push fresh brake fluid from the cup into the caliper by setting the unit t pressure, then hooking up the hose from the gun to the lid of the cup and the hose from the straw in the cup to the bleed nipple. Pressurize the cup lightly, open up the bleeder and voila!
Either way I plan to flush the front and rear brake systems.