hitting on a car starter (if it doesn't work) may work, if the grease in it has hardened with time. Car starters use a built-in solenoid to attach or pull the pinion to the big pinion on the flywheel by a slide mechanism. The same solenoid then gives contact to the real starter motor.
Then you only should use a wooden or plastic hammer, just to break loose the hardened grease. This may work sometimes but if you run into that issue, start collecting money for a new starter motor or have a very skilled person to clean the inside from any old grease and go on with fresh grease.
http://de.wikipedia.org/w/index.php?title=Datei:Automobile_starter_2.JPG&file...The most motorcycles (except BMW, Moto Guzzi etc.) have a free-wheeling clutch instead. No mallets allowed!