PURPOSE: To control a heating means at a predetermined temperature by feedback and prevent ignition of the fuel due to overheating by a method wherein the heating means and a sensor detecting the temperature of the heating means are provided in the crank chamber or the scavenging path of the two-cycle internal-combustion engine using the low-quality fuel.

CONSTITUTION: The heating part 48 of a glow plug 46, heating the mixture induced into a crank case, is provided in the scavenging path 38 of the two-cycle internal-combustion engine using the low-quality fuel. The temperature sensor 50, detecting the surface temperature of the heating part 48, is attached to the heating part 48 and the detected value thereof is inputted into a temperature controller 52 while the temperature controller 52 controls an output voltage from an electric source 54 to the glow plug 46 so that the temperature of the heating part 48 becomes optimum.