If you buy a travel insurance policy look and see if it includes 'athletic events' disclaimers. Lots of policies exclude anything that involves athletic pursuits, and they interpret those pretty broadly, including bicycle touring. a random day of bicycling in Europe probably won't be a problem, but riding 100km through Columbia day-after-day might be. Call the company and ask.

Also, a lot of policies require you to pay 'up-front' in country, then they re-imburse you when you get home based on submittal of bills, so make sure you have enough access to cash in the country you are visiting (lots of developing countries will make you pay cash for medical services).