Yikes...well the Darien Gap in Panama might be a bit of a problem. Check out this link
1. Try to find a bank that has branches in nearly all the countries you're crossing, and open up an account there. It will cut down on the cash you have to carry. Or at least a couple of banks...
2. Carry as many spare parts as you think is conceivable...who knows if in some backwoods portion of Honduras you'll be able to find stuff for it.
3. Avoid Colombia. Honestly, I'm all for adventure and traveling to many countries others woudl balk at (my next planned trip is Syria), but Colombia has lots of bad shit going on down there right now. And Venezuala moving that direction, to, with the Chavez stuff and drug money.
4. Get a guidebook on Mayan ruins in the area...you should be able to hit a ton of them with your own wheels...man, sounds awesome! I recommend Tikal, especially. Also, in the area of Merida, Mexico, there's a boatload of them, too...
5. Check out (on the web) how to BUY a replacement bike in some of the countries on your route. That way, if disaster strikes your wheels, your trip doesn't have to be ruined.
That's all I can think of for now...