Sport planes usually need a displacement size from the middle of the recommended range. Many aerobatic planes use the biggest engine possible which necessitates more throttle control from the pilot, but can result in better aerobatics. A glow plug will cause combustion by itself once the engine is running. Glow plugs do not require an on-board battery or ignition system and make model engine operation easier. The carburetor in model engines is very simple compared to full-size cars or planes.
Most engines come with detailed directions.
Always refer to those directions before operating the engine. They are easier to adjust, less prone to failure from high stress or misuse, and offer more power for their size and weight. Four-stroke engines fire every two revolutions. This equates to more torque, less propeller RPM, and a quieter running engine. However, four-stroke engines need more maintenance and are harder to adjust.