Which of these need to be changed in a two stroke reversing engine after stopping the engine to reverse direction?

In a two-stroke reversing engine, changing the direction of the engine requires adjustments to the fuel injection timing to ensure optimal engine performance and efficiency. The fuel injection timing is crucial because it dictates when the fuel is injected into the combustion chamber relative to the position of the piston. If the timing is not adjusted during the reversal of the engine, it can lead to poor combustion, increased emissions, and potential engine knocking.

When the direction of the engine changes, the dynamics of the engine operation also change. The timing must be recalibrated to account for the different conditions during the new direction of operation, ensuring that combustion occurs at the right moment in the engine cycle.

In contrast, while the other options may involve maintenance under different circumstances, they do not specifically need to be altered just because the engine is being reversed. The fuel filter, oil pump, and air intake valve settings are not typically changed solely due to a reversal and may only require attention during routine maintenance or if specific issues arise. Thus, adjusting the fuel injection timing is the essential step in preparing a two-stroke reversing engine for a change in direction.