is the water circulating in the coolant header tank? you should be able to see it with the cap ff and the bike Running,a leaking head gasket will also cause that.
adam bike doctor
October 2015
if the temp gauge needle's going straight into the red, no/low coolant, thermostat stuck shut, no/low engine oil engine semi-seizing up. If temp reads normal when engine stops must be poor fuel delivery from tank to carb/carb to inlet. dirt or water in carb or tank or filters.