What tool is used to set the clearance between the valve stem and rocker arm?

The feeler gauge is specifically designed to measure gaps or clearances between components, making it the ideal tool for setting the clearance between the valve stem and rocker arm. When making adjustments, the feeler gauge is inserted between these parts to ensure the correct amount of space is maintained, which is crucial for proper engine function. The use of a feeler gauge allows for precise measurement, ensuring that the gap lies within the manufacturer's specified tolerances.

Other tools mentioned serve different purposes; for instance, a torque wrench is used for applying a specific torque to fasteners, a caliper is primarily used for measuring external and internal dimensions or thickness of an object, and a straightedge is utilized to check flatness or alignment, but none are suited for measuring small gaps like a feeler gauge. Thus, the feeler gauge is essential for achieving the necessary precision in valve adjustments in small engine technology.