Abstract: A motor bicycle is provided with a main frame supporting a head tube operatively connected a steering shaft of a front wheel. The main frame includes a main tube which is connected to the head tube and extends rearwardly along the main body of the motor bicycle, and the main tube comprises two tube members extending rearwardly from the head tube with a certain angle in bilaterally oblique directions in a plan view. A helmet storage box is disposed in a space between the two tube members, the seat and the head tube so as to have an inner volume sufficient for accommodating a helmet or the like. This arrangement makes it possible to locate a fuel tank below the seat without changing the outer appearance of the motor bicycle.

Abstract: A motor bicycle is provided with a main frame supporting a head tube operatively connected a steering shaft of a front wheel. The main frame includes a backborn which is connected to the head tube and extends rearwardly along the main body of the motor bicycle and the backborn comprises two members extending rearwardly from the head tube with a certain angle in bilaterally oblique directions in a plan view. A helmet storage box is disposed in a space between these two members, the seat and the head tube so as to have an inner volume sufficient for accommodating a helmet or the like. This arrangement makes it possible to locate a fuel tank below the seat without changing the outer appearance of the motor bicycle.