So I was riding around with a buddy of mine that has an M50.  I lead because I obviously have the better bike.  He pulls up next to me at a light and says that my brake light is staying on.  Has anyone had this problem before and if so how did you remedy this problem?

Is brake light on when its standing and you switch on the ignition?
If not does brake light come on if you switch on lights? (sometimes if you got a short or anything both bulbs filaments can light up when you turn lights on.

Does front brake lever return fully out, if there's play due to front brake needing bleeding that may cause the contact in brake lever to stay contacted.

if your not resting foot on brake pedal check the rear brake lever is returning properly and that the spring that pulls the rear brake light light switch to turn light on isn't sticking. The switch body for back back light can be turned (it has a screw thread) to adjust tension and may need adjusting / cleaning every so often as rear brake linings wear and crud may collect on it. It is about halfway up the right hand side frame behind the air filter and battery.


It is unlikely to be a faulty front brake light switch as this has a small contact inside that moves back and forward when brake lever moves.



Hope this helps.

I am thinking (always a scary thought) that it is probably just the adjustment on the rear brake light switch.

I'm sure you looked at the cable from the pedal to the switch.  I'm voting for either the cable is sticking, where the spring connects the 2 cables, or the switch is bad.