Ex500 = GPZ500 Same bike better known as the ex500 in the U.S. One problem i found with my 1990 model is the magnets fell off inside the rotor.(after 50,000miles) BAD Glueing! check charging to the battery or even take the engine cover off to check the magnets for damage. Later models aparently have these reinforced. i.e. 1998 models +.