I rarely run a large diameter bit on my PC 7518 but ran a large diameter panel cutter today. This was a Freud bit with backcutter, on the label it recommended 12,000 rpm so I adjusted the speed control to the nearest setting of 13,000 before starting. I noticed the router speed would speed up and slow down with no load. As I ran the panel it seemed like the speed stabilized and ran stead as the panel was being cut. Is this normal for the speed to fluctuate with out a load?