Passport - Make sure your passport is valid for more than 6 months after your return date. Your passport isn't really a 5 year document, it is more like a 4 1/2 year. Countries will not let you enter them if your passport expires within 6 months of your entry stamp!
International Drivers Permit - These tend to only cost about $30-$40 and translate your licence into many different languages. Some countries require them, so just not a bad idea to have along. Don't forget your actual licence as well. In British Columbia you can get an IDP at BCAA.
Access to Money (Credit Cards) - It is always a good idea to have at least 2 different credit cards available. One mastercard and one visa. Unlike North America, not everywhere accepts both. Some bank machines wont give you money on one but will on another. As a Canadian in South America, I like Scotia bank for my visa card, as they have a decent prescence there and fees can be less.
Travel Insurance - We are using World Nomads. It is very important to make sure whomever you use actually covers motorcycle riding or you could end up royally screwed. World Nomads covers quite a bit and was reasonable. $300 cdn for 4 months of travel.
Imunizations and Shots - Check with a doctor or travel clinic for what is needed depending on your travel location. Since we are doing the entire Panamerican Highway, we ended up with a fair few needed. We got shots for Hepatitis (A & B), as well as Yellow Fever, Typhoid, Tetanus and measles/mumps/rubella. Also could have gotten rabies, but if exposed one still must go for more treatment anyways, and rabies was quite an expensive one.
Medical Kit / Prescriptions - Make sure any required prescriptions are filled with enough for the duration of your trip. You wont be able to get refills on the fly. I got additional prescriptions for travellers diarrhea and altitude sickness. I passed on anti-malarial pills as the price was too high or they had psychotic side effects. I do have some high quality repellent with me though. I also have a small first aid kit packed with all the typical essentials.