Research on an electrically controlled system which can stably maintain a constant engine speed, while carrying out choke operations using a choke valve when starting the engine, was carried out with the objective of constructing an electrically controlled auto choke system for a general purpose engine that can control both choke mechanism and engine speed with a single motor. Research was also carried out on a mechanism that could drive both the throttle and choke valves with a single motor.First, the throttle valve was fixed in the fully open position and the relationship between the choke valve mechanism and engine speed was analyzed. The relationship between the opening angle of the choke valve and engine speed could be formulated by second order transfer function. However, it became clear that transfer function parameters drastically changed depending on ambient temperature and plug seat temperature. Therefore, instead of using a proportional-integral-derivative (PID) controller, which is stable only under limited conditions, a self-tuning regulator was used to maintain a constant engine speed using a choke valve. By this, a constant engine speed could be controlled with a choke valve regardless of temperature change during operation.A mechanical part for an electrically controlled carburetor to drive both throttle and choke valves with a single motor was designed. This drives the gear, which holds the cam structure, with a single motor. The gear drives the throttle valve, and then drives the choke valve connected to the linkage system by the cam. In this way, the choke valve and throttle valve could be successfully operated without being affected by the other.From these results, an electrically controlled auto choke system for a general purpose engine, which could control both choke mechanism and engine speed with a single motor, was possible.