Ok are you saying its the bouncing that is repsonsible for the 2 rising events per cylce?
No, if my assumptions are correct, you're not getting exactly 2 rising events per cycle but sometimes 2, sometimes 3, sometimes only 1. Depending on you mechanical installation you may have two impulses because the magnetic field is hitting the sensor with two maximas. In any of these cases you should be able to filter the double edges out by comparing the times when they occur. What is your expected speed of the motor? 400rpm to 500rpm?