Question 4 DDE01 - Designated Duty Engineer - Unlimited HP

The Correct Answer is C **Explanation for Correctness (Option C):** Option C states: "With the particular piston positioned at TDC and the corresponding oil pan hand hole cover removed, inspect the lower liner bore through the crankcase opening." 1. **Positioning the Piston (TDC):** To inspect the *lower* part of the cylinder liner bore, the piston must be moved completely out of that area. The highest position the piston reaches is Top Dead Center (TDC). When the piston is at TDC, the entire lower portion of the liner is exposed, allowing for visual inspection. 2. **Access Point (Crankcase/Oil Pan):** The lower portion of the cylinder liner and the piston skirt are contained within the crankcase. To visually access this area from below, the corresponding hand-hole cover must be removed. On most large engines, this cover provides access to the connecting rod bearing and the inside of the crankcase/oil pan area, allowing a view up into the lower bore of the cylinder liner. **Explanation of Incorrect Options:** * **A) With the particular piston positioned at BDC and the corresponding oil pan hand hole cover removed, inspect the lower liner bore through the crankcase opening.** * **Incorrect Piston Position:** If the piston is at Bottom Dead Center (BDC), the piston skirt and rings completely occupy the lower portion of the liner bore, making inspection of that area impossible. * **B) With the particular piston positioned at BDC and the corresponding air box hand hole cover removed, inspect the lower liner bore through the crankcase opening.** * **Incorrect Piston Position & Access Point:** BDC obstructs the lower liner bore. Furthermore, accessing the lower liner bore is done via the crankcase/oil pan opening, not the air box opening. The air box is typically used to inspect the liner's middle section and ports (for two-stroke engines) or the top section (by removing the cylinder head). * **D) With the particular piston positioned at TDC and the corresponding air box hand hole cover removed, inspect the lower liner bore through the crankcase opening.** * **Incorrect Access Point:** While TDC is the correct piston position, the access point for the *lower* liner bore is through the crankcase/oil pan (as stated in C), not the air box hand hole. The air box is situated around the mid-section of the liner.