Changed front pads now rear brake not working

I finally got around to changing my front brake pads on my ‘07 vfr 800 with OEM pads, calipers and pistons cleaned with brake cleaner. Initially everything seemed good the front brakes felt great but it seemed like as I rode the bike the rear break had no resistance as if there is air in the line or something. I’ve always thought the linked brakes were good but now I’m cursing the complexity. I purchased the bike new in June 2009 so it’s been with me for nearly 15 years! Brake fluid is a bit over 2 years old, bike has under 20k miles so it’s a pretty clean and has been loved. Anyone have this issue?

 

Plenty of info on both forums on the braking systems. Do some searching and you'll find your bug!