NOVELTY - The system has a power management module, which divides electrical circuits into at least two power supply groups of different power supply priorities. Direct current is supplied first to the first priority circuit group, and then to the second priority circuit group after the power requirement of the first priority circuit group is completely met.    USE - For an electronic fuel-injection motorcycle.    ADVANTAGE - When there is no power in the battery, human power can be used which will be supplied first to the engine control unit to start the engine. During ignition, over use of the electrical loads of the motorcycle will not lead to a low voltage in the engine control unit or an engine stop. Ignition timing and fuel injection timing are accurately controlled by the engine control unit, reducing fuel consumption and air pollution.    DETAILED DESCRIPTION - An electrical system for an electronic fuel-injection motorcycle, includes an electrical generator which can be driven by an engine or human power. A rectifier is connected to the generator to convert the electricity into direct current. A battery is connected to the rectifier for storing the direct current. There are electrical circuits each connected between the rectifier and an engine control unit, or between the rectifier and the remaining loads of the motorcycle. There is also a power management module, which divides the electrical circuits into at least two power supply groups of different power supply priorities. A first priority circuit group is connected between the rectifier and an engine control unit, and a second priority circuit group. The converted direct current is supplied first to the first priority circuit group, and then to the second priority circuit group after the power requirement of the first priority circuit group is completely met. It is then supplied to the remaining priority circuit groups one by one according to their power supply priorities.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic electrical circuit diagram of the above electrical system.