I don't know the laws of other countries, but here in America, every state has different laws regarding motorized bikes. State law supersedes federal law here. In certain areas of Australia and the UK, motorized bicycles are completely illegal. They are federally banned in Canada, but some regions and provinces allow them. So motorbiking across the world could prove very difficult from a legal standpoint. You could be pulled over, have your bike impounded, you could even be arrested or deported in some places. You would need to research the laws in every country and state or province you plan to travel through, and figure out the route that is most friendly to you legally.