I have a 1982 gl1100a that is an awesome bike but when I ride on the interstate at about 80+ my bike will over heat no matter what. Riding in town or on the highway at 5 mph to 70mph I will sit at normal operating temp even in 90+ degree weather. Only on the interstate it over heats. Anyone have any ideas as what could be the problem? Could it be thermostat? Waterpump? Any help would be very appreciated!