Which component is checked for free rotation after adjusting main bearings?

After adjusting main bearings, it is essential to check the crankshaft for free rotation. This is primarily because the main bearings support the crankshaft and allow it to rotate smoothly within the engine block. The adjustment process can affect the alignment and clearance of the crankshaft, and ensuring it rotates freely is critical for the engine's overall performance and functioning.

If the crankshaft does not rotate freely, it could indicate issues such as excessive bearing clearance or improper alignment, which can lead to more severe mechanical failures if not addressed. Free rotation of the crankshaft signifies that bearings have been correctly adjusted, allowing for optimal engine operation without undue friction or resistance.

Other components, such as the cylinder head, piston rings, and camshaft, play significant roles in engine function and performance, but they are not typically assessed for free rotation specifically after main bearing adjustments. The focus on the crankshaft in this context hones in on ensuring the foundational part of the engine's rotation is intact.