To improve an energization circuit for a heat-operated actuator so that a starting valve is closed at appropriate speed and timing after a warm-up.

A starting valve 10 adapted to be closed at high temperature by a heat-operated actuator A is interposed in a starting fuel passage that connects the fuel chamber of a carburetor and a downstream portion of an intake valve in regard to a throttle valve. To an energization circuit for heating the heat-operated actuator A, a PTC thermistor 53 set near to the actuator A and an NTC thermistor set near to an internal-combustion engine are connected in series.