How can the air/fuel ratio be restored to the optimum 14.7:1 at higher elevations?

The optimum air/fuel ratio for combustion in small engines is typically around 14.7:1, which is necessary for efficient operation and minimal emissions. As elevation increases, air density decreases, leading to a lower availability of oxygen for combustion. To maintain that optimal ratio at higher altitudes, it is necessary to reduce the amount of fuel being delivered to the engine.

This is because, at higher elevations, there is less oxygen available in the same volume of air, so a proportionate decrease in fuel is needed to maintain the proper air/fuel mixture. Adjustments can be made to the carburetor settings or by changing the jet sizes to allow less fuel to enter the engine, thereby restoring the necessary air/fuel ratio to 14.7:1. By implementing this change, the engine can continue to perform efficiently without running rich, which can lead to fouled spark plugs and increased emissions.

The other options do not effectively address the issue of maintaining the correct air/fuel balance at higher elevations. Increasing fuel flow would exacerbate the rich mixture problem, adjusting ignition timing does not directly impact the fuel delivery, and adding synthetic oil does not affect the air/fuel mixture at all.