Well, that's a big kick in the nuts. During my ride yesterday, my brakes were quite good, and today they were much worse, ziptied the lever after a quick test ride, and an hour later, the lever's dead. No pressure at all..
It's common practice to ziptie the lever shut overnight to let air bubbles escape. It also tells you if there's a problem with the system which seems to be the case with mine.
Freddy, someone accidentally discovered that storing with the levers partially compressed overnight allowed the system to improve.
Many (including me) have tried it {on a hard to bleed system} and it does seem to help.
The only think I can think of that seems to make sense is; pulling the lever back compresses' the trapped air, and opens a valve in the master cylinder that allows compressed air to migrate up into the reservoir.
Ride safe, Ted
they rise to the master reservoir? Either way, it's supposed to be able to hold pressure overnight
That's not so. Any air trapped in the line cannot escape/rise into the reservoir because the port thru which it would enter the reservoir is closed when the lever is moved from the released position. Check how a master cyl works.
It may allow any air to rise to the master cyl so that when the lever is released, it immediately enters the reservoir.