I made the mistake of thinking this bolt was somehow related to draining coolant. But I find its on the other side of the motor. (no wise cracks).
It was really a dumb move but I need to know what I did. It takes a flat head screw driver and has tick marks to make adjustments. YOu need to loosen a bolt that CLAMPS you from turning that bolt.
But i loosened it and turned it. WHat does this do?

 

What year and model is this bike? Better picture would be great.

OK, now I realize you are working on a CBR 1000F.

That is the Balancer Backlash adjustment. You adjust it while it is cold and not running.

1. Loosen the pinch bolt and turn the shaft Counterclockwise until it stops, then clockwise by one (1) graduation.
2. Apply locking agent tot he threads of the pinch bolt and tighten it securely.