An engine system comprising: an engine; a battery; a crankshaft driving device that is configured to rotate a crankshaft of the engine by electric power of the battery; a controller that is configured to control the engine and the crankshaft driving device in any control mode of an idle stop mode and a non-idle stop mode; and a kick starter that is configured to be operated by the rider in order to rotate the crankshaft, the engine system comprising a switcher that is configured to be operated by a rider in order to switch the control mode of the controller between the idle stop mode and the non-idle stop mode; wherein the controller, in the idle stop mode, is configured to control the engine and the crankshaft driving device such that the engine is configured to be stopped in the case where a predetermined idle stop condition is satisfied, and wherein the controller is configured to control the engine and the crankshaft driving device such that the engine is configured to be re-started in the case where it is after the satisfaction of the idle stop condition and a predetermined re-start condition is satisfied, in the non-idle stop mode, the controller is configured to control the engine such that the engine is configured to not be stopped even in the case where the idle stop condition is satisfied, and wherein the controller is configured to prevent start-up of the engine in the case the crankshaft is configured to be rotated by an operation of the kick starter with the engine that is configured to be stopped and the control mode that is configured to be set to the idle stop mode, and wherein the controller is configured to allow the start-up of the engine in the case where the crankshaft is configured to be rotated by the operation of the kick starter with the engine that is configured to be stopped and the control mode that is configured to be set to the non-idle stop mode. an engine; a battery; a crankshaft driving device that is configured to rotate a crankshaft of the engine by electric power of the battery; a controller that is configured to control the engine and the crankshaft driving device in any control mode of an idle stop mode and a non-idle stop mode; and a kick starter that is configured to be operated by the rider in order to rotate the crankshaft, the engine system comprising a switcher that is configured to be operated by a rider in order to switch the control mode of the controller between the idle stop mode and the non-idle stop mode; wherein the controller, in the idle stop mode, is configured to control the engine and the crankshaft driving device such that the engine is configured to be stopped in the case where a predetermined idle stop condition is satisfied, and wherein the controller is configured to control the engine and the crankshaft driving device such that the engine is configured to be re-started in the case where it is after the satisfaction of the idle stop condition and a predetermined re-start condition is satisfied, in the non-idle stop mode, the controller is configured to control the engine such that the engine is configured to not be stopped even in the case where the idle stop condition is satisfied, and wherein the controller is configured to prevent start-up of the engine in the case the crankshaft is configured to be rotated by an operation of the kick starter with the engine that is configured to be stopped and the control mode that is configured to be set to the idle stop mode, and wherein the controller is configured to allow the start-up of the engine in the case where the crankshaft is configured to be rotated by the operation of the kick starter with the engine that is configured to be stopped and the control mode that is configured to be set to the non-idle stop mode.