For the first 21 months of our trip starting February 2014, we sought the following insurance:

• Navigator Travel Insurance (Silver policy)
• Various road insurances through South and Central America

Once in the US from November 2015 onwards, we sought new coverage for the States and Canada:

• STA Travel (Adventure Plus policy for general travel and health insurance.)
• Progressive (The cheapest on road policy we could find.)

See this great link for reviews on US based motorcycle insurance.