If the flywheel key shears on an engine with an ignition armature, what happens to the spark?

When the flywheel key shears on an engine with an ignition armature, the timing of the spark is affected. The flywheel key is responsible for maintaining the alignment between the flywheel and the ignition timing mechanism. If this key shears, it allows the flywheel to rotate out of its intended position.

As a result, the ignition armature may still produce a spark, but it will occur at the wrong time in the engine's cycle. Proper ignition timing is crucial for optimal engine performance since the spark needs to ignite the air-fuel mixture at the precise moment in the compression stroke. When the timing is off, the spark may occur too early or too late, leading to poor engine performance or failure to run.

This situation exemplifies the importance of components like the flywheel key in maintaining the proper synchronization required for the engine to function effectively.