I was cleaning my bike this evening when I noticed that when I apply the rear brake pedal my brake light does not illuminate, It's only when I apply the front brakes that the rear brake light illuminate. Is this right??

At the back foot peg lever, go look for a spring dangling off or loose at the brake pedal arm?
If the spring is on, press real hard on the brake pedal see if the light now comes on?
Remove seat. If you have a 17mm open end wrench, you move the big nut, hold the brake switch, and do not make a full turn, meaning, this should get to the brake's sensitivity back to a few turns using a few flats of that 17mm nut.

The other variables are the connection of the switch or the switch itself.

Okay, I have to press real hard to get it to illuminate, but that 17mm nut is in a tight fit!

I like to be able to illuminate the brake light w/o any braking.........use it basically as a signal before braking. I set the front up for that. Since pretty much only use the rear in addition to the front....very seldom just rear......I never cared to mess with. It is a funky design with that spring........

My rear sets came with a pressure switch in the banjo joint.

Try this. Use a scribe or file/grind an old flat screwdriver so it will bite into, meaning, not slip on the 17mm flat, you look down at the switch, move the nut to the right, or clockwise. Hold the switch, move the nut. This moves the switch up which moves the spring taught. Apply pedal for sensitivity you keep moving flat after flat around.

Hub
This is a pain in the ass!!

Problem solved, Just remove the RT side foot, there is enough cable there to allow you to make adjustment on that not.

If I remeber correctly, there is a threaded black plastic tube that you turn in or out to add tension to the spring that goes to the switch. You can see the spring behind the oEM heel guard in this pic.

I switched to aftermarket rearsets and have a pressure switch also. WOrks good. Actually, many people just leeave the rear brake without the brake light hookup. You usually use the fronts at the same time when you brake anyway. Still good to have a brake light switch for the rear on the street.