If you think your bike is overheating, don't panic, there is often a simple explanation.
First off, air cooled bikes do not often overheat. They are designed to cool themselves when operated normally. Note, that normal operation implies that the bike is moving. If you turn your bike on and let it idle and then go inside and watch TV for 30 mins on a hot day, it might overheat. But most air cooled bikes will do just fine even in stop and go traffic on a hot day. If you feel random gusts of hot air on your legs while riding your air cooled bike, usually thats normal.
Liquid cooled bikes can be higher performance machines because the extra heat produced is dealt with by the cooling system. Sometimes these systems fail. So, lets see a couple common problems: