There are three types of insurance the Adventure Traveller may want to think about:
Covering expenses if you hurt someone else with your bike (Third Party Liablility)
Covering the cost of fixing or replacing your bike if it is damaged or stolen (Motorcycle Insurance)
Covering expenses if you get sick or injured (Travel insurance)
Third Party Liability
Most of the time you have a choice. However, in many countries you are required by law to purchase a basic third party liablility policy. In some cases they won't give you the Temporary Vehicle Permit without showing evidednce that you have already purchase the insurance for that country. In other cases, you are required to have it, but you can get into the country without it and bad things may happen if the Police stop you and you don't have it. In other cases it is optional.
Some people claim they have BSed their way through Police stops by claiming they have a multi-country insurance coverage. Maybe they exist, I don't know. On a number of occaisions I asked for such an animal or asked if the "multi-country" policy I bought in another country would work and was told each time the insurance had to be issued by the country you are in.
Obviously it's your decision whether to get insurance in any country. I usually got it when it was a requirement and didn't when it wasn't. In Colombia, it took me a couple of days to find an insurance office that would sell me a policy. In Ecuador, there is an insurance vendor at the border crossing but their computer was down and they told us to buy it in Quito - a day away. Went to half dozen insurance agencies and banks and never did find someone to sell me the specialize policy required. Was there a month and, I guess I was fortunate to not get stopped or get in an accident.
Why bother getting third party liability insurance when not stipulated for your permit? In most (all?) Latin American countries, if you are involved in an accident, the police will arrest all parties and confiscate all vehicles until they sort out who is at fault. Since you are obviously a wealthy Gringo (all Gringos are deemed to be wealthy), you are likely deemed to be at fault . . . even if you weren't. A call to your local insurance company will result in them providing a person to advocate for you, who understands the local system and can get you and your bike out of the clink a lot faster. I never was involved in such an accident but, that was my theory on how it would work.
Mexico - You are required to buy Third Party Liability insurance when in Mexico. Optionally, the insurance companies will also insure your bike. I have always used an online Agent Adventure Mexican Insurance - get it all done before you leave.
Insure your bike? I didn't. Try to get secure parking at night and keep your senses sharp for people who may wish to separate you from your bike.
I have heard of some riders buying policies prior to departure to cover loss of their bike while travelling in many differrent countries. You will have to check the forums and do some Googling to see where people are buying bike insurance and if it is worthwhile. I think most travellers skip it.
What happens to your bike if you get injured or can't continue to ride? Some end up with Motorcycle Extraction Insurance as part of another policy. If you buy a medical extraction policy from MedJet, you can add on an extraction rider for something like $15. Also, check your Travel Insurance - they may provide extraction coverage - mine did.
A relatively inexpensive health insurance. They will cover medical expenses if you get sick or are injured outside your home-country. They will usually provide Medi-Vac evacuation if you are seriously injured or at least a flight home if you aren't seriously injured.
If you are Canadian, I can't say enough good about the Travel Insurance package provided by RBC Insurance. I've had two major claims, one involving a Medi-Vac and the other they bought me two seats on a schecualed flight and surprised me by bringing my bike home. First class service, didn't try to cheap out on anything and were very helpfull. If you are not Canadian, shop around for a company with a good reputation and full coverage. I've heard anecdotal reports of hospitals refusing to provide care until payment was assured. My insurance also had agents who were fluent in Spanish and were able to easily converse with Doctors and staff.
If your Travel Insurance does not include evacuation coverage, you can look at MedJet who will provide extraction and has a good reputation