Question 18Motor Plants - 1st Asst/Chief

The correct answer is B) spring surge. Bouncing of the valve gear in a diesel engine can be caused by spring surge, which occurs when the valve springs are unable to keep up with the rapid opening and closing of the valves during high-speed operation. This can lead to the valve train components, such as the valve stems and rocker arms, losing contact with each other, resulting in valve bounce. The other options are incorrect because: A) Prolonged high-speed operation can contribute to spring surge, but it is not the direct cause of valve gear bouncing. C) Worn valve seats may affect valve sealing, but they do not directly cause valve gear bouncing. D) Excessively tightened spring retainers can also contribute to valve gear bouncing, but spring surge is the primary cause.