front brakes/rotors 940 abs sensor acting up?

[knosal]

Hello. I just installed rotors/brake pads on a 940 sedan year 93.
I did lightly clean the abs sensor at each front wheel, and once everything was put back together, i took the car out for a test drive. The abs kicked in and started to grap the right front tire at each stop, pulsating. I removed both wheels,rotors,pads, and lightly sanded the inner tooth wheel on the hub, and lightly picked off any debris on the sensor. I then air blew off any matter remainging. I again took the car out for a road test, and noticed a big improvement, but still some pulsating on the left front tire. Is there a setting or gap measure that is suppose to be between the sensor and sprocket wheel for the abs. I noticed the right front was a hair shorter in gap compared to the left. Both sensors are clean as well as both sprockets. I am at a loss as to why this should be occuring. Any thoughts???