AG Mechanics CDE Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

When checking the valve tappet clearance, it is crucial to position the piston at the top of the compression stroke. This is the correct answer because setting the piston at this specific point ensures that both the intake and exhaust valves are closed, providing the most accurate measurement for the valve clearance. By having the piston at the top of the compression stroke, you prevent any interference from the valves during the adjustment process.

Option B, exhaust stroke, is incorrect because during this stroke, the exhaust valve would be open, which could lead to misreadings in valve tappet clearance. Option C, intake stroke, is also incorrect because during the intake stroke, the intake valve would be open, similarly causing inaccurate measurements. Option D, power stroke, is not the ideal position for adjusting valve tappet clearance, as during this stroke, the piston is not in the position where both valves are closed, compromising the accuracy of the adjustment.