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 motorcycle is provided with a body height adjustor capable of adjusting the body height of the motorcycle by changing lengths of front suspensions and a rear cushion unit. The body height adjustor includes a first hydraulic jack for extending and retracting the front suspensions, a second hydraulic jack for extending and retracting the rear cushion unit and a body height adjusting unit to transmit hydraulic pressure of hydraulic fluid in the rear cushion unit to the first and second hydraulic jacks through hydraulic hoses. The rear cushion unit is provided with a rear oil damper and a coil spring against which the second hydraulic jack abuts and the initial load of the coil spring is changed by the hydraulic pressure in the rear cushion unit. The second hydraulic jack is movable in a direction towards the coil spring with respect to the rear oil damper to change the initial load of the spring.

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.