Under normal air-cooling(Riding) the CX/GL500 engines should run with the temp needle in the nominal position mark on the temp gauge,
http://www.youtube.com/watch?v=TiPzLGMv ... 37#preview
These engines should run around 80/85 Deg C(176/185 °F ) at the cylinder jacket at the middle rear of the Cylinder below the Head cover.
If stopped in traffic or left idling the needle can go up to 3/4 of the gauge.It should NEVER go into the red.
My two CX now thermostatically controlled electric fan conversions,
viewtopic.php?f=7&t=209
so never go above the middle of the temp gauge and then the fan/s drive my temps back down to the nominal mark just like a car system.
You should flush the cooling system and if the bike is new to you check and or renew the Thermostat and Radiator caps.These can be had cheap from Autozone type shops.You should also flush the system and change the coolant,
http://www.pdsrecording.site90.com/cxgl500/Coolant.htm