There is 2 types of insurances I think you need.
- Health insurance:
As it is usually cheaper to buy a travel insurance (Auslandskrankenversicherung) I closed mine at ADAC Germany. It costs ~ € 240,- (for 6 months) and includes home flight in case of any emergency. For this time you can ask your health insurance company if they put your contract on hold and keep it as an entitlement (Anwartschaft). Once you are back you will get your “normal” contract and all benefits you had before.
- Bike insurance:
You are enforced in South America (like in most of the countries in the world) to have an insurance for your bike.
There is at least an easy way to get a combined insurance policy for the following countries: Brasil, Chile, Argentina, Bolivia, Paraguay and Uruguay. The costs are ~ € 35,- per month and you can get directly in contact with Gisela Speiser in Argentina (firstname.lastname@example.org).
Beside the above you need:
- International driver license (costs: ~ € 10,-)
- International registration document (costs: ~ € 15,-)
(Internationaler Zulassungsschein / Fahrzeugschein)