An engine misses in both the right and left positions of the magneto switch. The quickest method for locating the trouble is to

When an engine exhibits a miss in both the right and left positions of the magneto switch, it indicates that the issue likely lies within the ignition system rather than the magneto itself, since both magnetos are showing the same symptom. The quickest method for identifying the problem is to check for one or more cold cylinders, as this can quickly point to a failure in the ignition or fuel delivery system.

A cold cylinder often indicates that it is not firing properly due to issues such as improper fuel delivery or a malfunctioning spark plug. By checking the temperature of the cylinders or observing engine operation, you can quickly determine if one or more cylinders are not generating power as expected, which would further lead to diagnosing the underlying issue.

This process is more immediate than performing a compression check or inspecting the fuel system, which could take more time and might not directly reveal the ignition-related issue causing the engine miss in both switch positions. Checking each spark plug may also be useful but is usually part of a broader inspection rather than a quick diagnostic step. Thus, verifying cylinder temperatures provides the most direct approach to diagnosing the problem.