I have seen other bikes do this and the most common fix was to BURP the radiator. To do that, you take the radiator cap off, start up the bike and let it warm up. While the bike is idling, check to make sure you have the proper level of fluid under the cap. If the bike has air in the system, you will see air bubbles coming to the top where the cap is and this will proceed until the air bubbles go away under a constant idle. I have seen some bikes that will dribble a little fluid out during this process, but eventually the bubbles go away. When they do, put the radiator cap back on and give the bike a few throttle blips to cycle the fluid a little more. Then, turn the bike off and let it cool or... go for a ride and see if you still have heat issue.
13' KLR 650, 06' GL1800
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