A saddle type vehicle comprising: an internal combustion (IC) engine , the internal combustion engine comprising: a crankcase ; a crankshaft , the crankshaft being supported by the crankcase , the crankshaft configured to receive rotary motion on burning of air and fuel mixture within the IC engine ; an output shaft , the output shaft being configured to receive rotary motion from the crankshaft , the output shaft being operably connected to provide rotary motion output to a rear wheel of the saddle type vehicle ; a first transmission mechanism interposed between the crankshaft and the output shaft , the first transmission mechanism configured to provide variable torque rotary motion output at the output shaft ; and an engine sprocket being exposed in a width direction of the vehicle through a clutch cover wherein the clutch cover enclosing a left-hand side of the IC engine in the width direction; an electric motor unit , the electric motor unit being detachably mounted on the external surface of the crankcase of the IC engine , the electric motor unit comprising: an electric motor , the electric motor being operably connected to the output shaft to provide a parallel torque assist at the output shaft along with the IC engine ; a second transmission mechanism , the second transmission mechanism being interposed between the electric motor and the output shaft to provide torque multiplication rotary motion output at the output shaft ; wherein the electric motor unit comprises a first housing member and a second housing member assembled to form a space to accommodate the electric motor and the second transmission mechanism ; and wherein the second housing member of the electric motor unit being configured to attached to the clutch cover . a crankcase ; a crankshaft , the crankshaft being supported by the crankcase , the crankshaft configured to receive rotary motion on burning of air and fuel mixture within the IC engine ; an output shaft , the output shaft being configured to receive rotary motion from the crankshaft , the output shaft being operably connected to provide rotary motion output to a rear wheel of the saddle type vehicle ; a first transmission mechanism interposed between the crankshaft and the output shaft , the first transmission mechanism configured to provide variable torque rotary motion output at the output shaft ; and an engine sprocket being exposed in a width direction of the vehicle through a clutch cover wherein the clutch cover enclosing a left-hand side of the IC engine in the width direction; an electric motor , the electric motor being operably connected to the output shaft to provide a parallel torque assist at the output shaft along with the IC engine ; a second transmission mechanism , the second transmission mechanism being interposed between the electric motor and the output shaft to provide torque multiplication rotary motion output at the output shaft ; wherein the electric motor unit comprises a first housing member and a second housing member assembled to form a space to accommodate the electric motor and the second transmission mechanism ; and wherein the second housing member of the electric motor unit being configured to attached to the clutch cover . wherein the electric motor unit comprises a first housing member and a second housing member assembled to form a space to accommodate the electric motor and the second transmission mechanism ; and wherein the second housing member of the electric motor unit being configured to attached to the clutch cover . <EOS>