What must be ensured about the intake valves when adjusting the slave valve clearance?

When adjusting the slave valve clearance in an engine, it is critical to ensure that the intake valves for the cylinder being adjusted are fully closed. This is necessary because if the intake valves are not in the closed position, the clearance measurement may be inaccurate. The adjustment process involves measuring and setting the gap between the valve and the rocker arm or lifter when the valve is seated completely, which allows for proper alignment and operation of the engine.

Having the valves closed on the cylinder ensures that any movement in the valve is minimized and that the clearance reflects the true condition during operation. This step guarantees that the valves can open and close properly without any interference or binding, which is essential for optimal engine performance.