The ignition system is the starting system for your small engine. Whether you start the engine with a pull rope or the turn of a key on an electric start motor, you're relying on the ignition system to produce a spark inside the combustion chamber.
Small Engine Ignition Parts
- Flywheel with magnets
- Coil or Armature
- Push Button starting or Pull Cords (depending on your engine type)
- Spark Plug Lead
- Spark Plugs
- Key Switch
- Kill Switch
When you start your lawn mower or small engine, you turn the flywheel and its magnets pass the coil (or armature). This creates a spark. The ignition system coordinates the timing so that the spark will ignite the air-fuel mixture in the combustion chamber just as it reaches maximum compression in each engine cycle- thus, maximizing the engine’s power.
Once the engine is running, the flywheel keeps rotating, the magnets keep passing the coil and the spark plug keep firing based on a specific timing.
Types of Ignition Systems
- Solid-state systems: the more modern option, these systems use a tiny transistor in the coil or armature to close the electrical circuit that travels through the spark plug lead to the spark plug(s).
- Breaker point systems: used on engines made before 1980, these systems use a mechanical switch instead of a transistor to close the electrical circuit used to produce a spark.
Common Flywheel Problems
If you are experiencing ignition timing issues, this is most often due to a sheared flywheel key. You can also test the flywheel magnets for any potential issues.
For information regarding this, please visit our Inspecting the Flywheel and Key FAQ.
Common Spark Plug Problems