Default Root is gone after flashing stock kernel

I need help, I can't get root access back after flashing stock kernel...
Actually the first time that phone boots I got root but is gone after reboot

I already tried re-flashing SuperSU lastest version, but nothing works...

Any idea?

Maybe need a full wipe, but I dont want to lose all my apps data/savegames, and I can't back up anything cause titanium back up needs root
Nexus 4 16Gb
Nexus 5 32Gb
OnePlus One 64Gb