Final answer:
Magneto timing drift is caused by erosion of the breaker points and wear of the distributor cam, which is responsible for opening and closing the contacts of the breaker points in the ignition system of an engine.
Step-by-step explanation:
Magneto timing drift is caused by erosion of the breaker points and wear of the distributor cam.
The distributor cam is a rotating component in the ignition system of an internal combustion engine. It is responsible for opening and closing the contacts of the breaker points, which control the timing of the ignition spark.
As the cam wears down, it can lead to inconsistent contact with the breaker points, resulting in timing drift and poor engine performance.