The pulser coil picks up the timing signal from a flywheel magnet and instructs the CDI when to fire..
The Pulser Coil, (often called Pickup Coil, or Timing Coil) is responsible for providing the timing signal to the ignition control box on modern motorcycles with solid-state ignition systems.
The majority of motorcycles from the late 1970's and up use this system for reliable, accurate, and low maintenance ignition control.
On previous models, points-controlled systems were used, and while cheap and simple, they required routine maintenance and component replacement to ensure reliability.