"You need a new piston, valve guides, stator, and counter-shaft balancer"
In layman's terms you'd say:
"There are some internal parts that need replaced"
Student: Uh, I don't understand. Can you give that in layman's terms?
Teacher: When you squeeze a balloon to half it's size, it is harder to squeeze right? This is because the pressure is doubled. Get it?
Student: Uh, Yah!