Handheld engine-driven working machine

A handheld engine-driven working machine comprising:

• an internal combustion engine which includes a cylinder, a crankshaft, a piston disposed in the cylinder and connected to the crankshaft, and an ignition plug disposed in an upper portion of the cylinder;
• and
• an ignition control device activating the ignition plug;
• wherein the ignition control device can switch its control between a normal mode and an operation mode,
• wherein when acceleration is performed during the normal mode, the ignition timing is set by the ignition control device so as to, within a medium speed range, be advanced from a first BTDC angle to a second BTDC angle as the rotational speed increases and, within a high speed range, be maintained at the second BTDC angle,
• wherein when acceleration and deceleration are performed during the operation mode, the ignition timing is set by the ignition control device so as to, within the high speed range, be maintained at the second BTDC angle, and within the medium speed range, be maintained at the second BTDC angle as the rotational speed decreases,
• wherein at any rotational speed within the medium speed range, the ignition timing during the operation mode is advanced more than the ignition timing during the normal mode, and
• wherein when deceleration is performed during the normal mode, the ignition timing is set by the ignition control device so as to, within a medium speed range, be retarded from a second BTDC angle to a first BTDC angle as the rotational speed decreases.