Engine: Bore Stroke :100 mm (3.937 in) x 82 mm (3.228 in) , Compression Ratio :9.5 : 1, Engine :644cc (39.3 cu. in), 4-stroke, air-cooled, OHC , Fuel System: MIKUNI BST40, single , Ignition: Electronic ignition (CDI) , Lubrication :Wet sump , Starter: Electric ,