Which of the following is not a method used to start internal combustion generator sets?

The method of starting internal combustion generator sets includes various techniques that utilize different mechanisms for initiating engine operation. Manual cranking is not commonly used as a practical starting method in modern generator sets.

Compressed air to cylinder starting is a technique where air is compressed and injected into the combustion chamber to initiate the engine's operation. This method is effective for engines that require high torque to start, especially in larger engine applications. The electric method involves using an electric starter motor powered by batteries to crank the engine's flywheel until it starts. This is the most common method in standard gasoline and diesel internal combustion engines.

The compressed air starting motor utilizes compressed air to power a starter motor that turns the engine over, which is another reliable mechanism used in larger engines, such as those found in some industrial applications.

In contrast, manual cranking involves physically turning the engine's flywheel using a crank, which is labor-intensive and impractical for the majority of internal combustion engine designs currently in use. Consequently, this method is not considered a standard practice for starting generator sets today.