A brief history of motorcycle ignitions
Unlike the automotive industry, there have been many systems used on motorcycles. It also gets confusing that over the years, terminology for each system has been swapped around and used to describe other systems.
Most motorcycles manufactured before the 1980's either used a magneto or were points-operated on a 6 or 12 volt system. By the late 1970's, the first steps were made to use electronics, i.e. transistors to provide the switching of the coil as opposed to using points.
The transistorized systems TCI (Transistor Controlled Ignition) only provided the switching of the coil, and the advancing of the spark (Timing Control) was done by the triggering rotor mounted on the end of the crankshaft. The rotor had mounted weights and springs that separated it from the crank and allowed the rotor to move independently of the crank creating timing advance as the revs built up; this system applied to both CDI and TCI units.
The CDI (Capacitor Discharge Ignition) was also used during this period, the CDI was mainly used on 2 stroke engines and the larger capacity single cylinder 4 stroke engines, such as Yamaha XT/TT range, as this system was more effective at keeping plugs clean due to a higher energy spark. On earlier models the voltage was generated by the Stator (300-400v) to charge the capacitor, later as electronics improved the Battery CDI was introduced, this supply used 12v and a small transformer in the CDI unit to step up the voltage (300-400v) to the capacitor.
In the early 1980's the units started to incorporate the advancing of the spark into their electronic control circuit and the rotor became fixed on the end of the crank shaft. i.e. Electronically Advancing CDI and TCI.
The late 1980's saw the introduction of digital technology into most of the manufacturer's ignition systems. This enabled more data to be stored for more complex timing curves; then the early 2000's saw the introduction of ECU (engine control units). These were very similar to automotive units and again allowed complex control of the engine to meet the modern emission standards, etc.