Final answer:
The question is misaligned with the provided scenario. However, for the provided physics scenario, the magnitude of the normal force between the piston and the cylinder is 300 N when dry, and less than 300 N when oiled due to reduced friction.
Step-by-step explanation:
The installation of a magneto on an engine is not directly related to the physics question provided about inserting pistons into cylinders. However, the physics question can be answered by understanding that the magnitude of the normal force between the piston and cylinder would be equal to the force exerted to insert the piston if the motion occurs horizontally without any other forces acting, such as friction or gravity. Therefore, if a physics major exerts 300 N of force to insert a dry steel piston into a steel cylinder, the normal force is also 300 N in magnitude. When the steel parts are oiled, the required force would be less than 300 N since the oil reduces friction, making it easier to insert the piston.