So i recently bought an 02 f4i. I've slowly doing all the maintenance. I just changed the rear brake pads and bled the system with a bleeder and all. While riding the next day i was going about 60 down the street while my bike started slowing down suddenly then to a complete stop. Turns out my rear brake somehow self pressurized. I couldn't pump it or get it to unstick until i released pressure through the bleeder valve which then freed it what can be causing this?

 

To much brakefluid in the reservoir, don't go over the max line and you should be good to go next time