When checking valve clearance on a four-stroke engine, how should the crankcase cover be positioned?

To check valve clearance on a four-stroke engine accurately, the crankcase cover should be positioned in place with the bolts correctly tightened. This ensures that the engine is sealed appropriately, allowing for accurate measurements and adjustments without any interference from external factors.

Having the cover securely tightened helps maintain consistent conditions within the engine, ensuring that the rocker arms and valves are in the correct position during the clearance measurement. It reduces the likelihood of any changes due to vibrations or slight shifts in the engine components that could lead to inaccurate readings.

When the cover is off the engine, it exposes internal components to debris and contaminants, which could affect engine performance and measurements. Similarly, if the cover is loosely placed or only in place without being securely tightened, there still can be movement or misalignment that could compromise the accuracy of the valve clearance check. Thus, ensuring that the crankcase cover is properly fitted and tightened is critical for achieving reliable results when assessing valve clearance.