The present invention discloses an engine device for motorcycles in which a starter motor for transmitting drive force to a crankshaft through a reduction gear train can be disposed closer to the crankcase. The engine has a starter motor with a motor shaft, a crankshaft, and a reduction gear train for transmitting drive force of the starter motor to the crankshaft. The reduction gear train includes first gears supported for rotation on the first support shaft disposed parallel to the motor shaft of the starter motor, second gears supported on the second support shaft disposed parallel to the first support shaft, third gears supported on the generator shaft disposed parallel to the second support shaft, and a starter gear provided on the crankshaft disposed parallel to the generator shaft. The motor shaft of the starter motor is located closer to the generator shaft than the first support shaft.