well you will need to get that Form "temporario importation del vehiculo" at the aduana. In case you have two bikes in one box, you will have to have strong nerves, since they will make a big thing out of it, that it would not work to import themand so on. Well it worked but it needed time. Carnet will help you but it is not really necessary. AND: Do not show them to any other costum. We where just once asked for it but after we told them that we would not have it, they arranged it without.
When arriving at Valparaiso, the costums is not right next to the harbour (more to the north), so organise all the papers before you go to the harbour, since it will need time there. You will not need more than your export paper, paper from the transport company, passports and the carnet. We needed 1 day to get our bikes out of the costums area at the port.
Well, thats about all at the moment.
have a nice ride