Although not absolutely necessary, it is strongly recommended that a gyro be used in every helicopter. Controlling an overly sensitive tail of a helicopter is most frustrating and the gyro can help make the flying much easier and more pleasurable. Gyros are made by most radio manufacturers for operation compatable with their systems. When purchasing the helicopter engine, the muffler is not included. Usually the muffler comes with the helicopter kit.
Different motors facilitate different starting methods.
Some come with a pull start system for very simple starting. Others use a cone start where an electric starter is used in a manner similar to starting an aircraft. Still others use an electric starter and a belt for starting. Since the helicopter is purely a mechanical device, tools for assembly usually include items such as screw drivers, ball drivers, nut drivers, wrenches, pliers, etc. In addition to these there are a couple of specialty tools that come in handy when assembling and setting up the mechanics of your helicopter.