The carnet is a leaflet, where the details of you bike such as frame number and engine number, will be printed on each page. When you enter a country, thats in the carnet-system, such as Iran, the customs will give an entry stamp, and so your bike is allowed temporary import into this country. When you exit, the customs will give an exit stamp, and you need to make sure you´ll get it, as otherwise there may be problems.

There´s usually a considerable bond, which you need to leave to get the carnet, becaus in case your bike will not leave a carnet country, they will contact the issuer, and demand all taxes and duties be paid. In Finland, this bond was 5000 euros minimum, could be a bit cheaper elsewhere. Usually it can be handled as a bank bond, like a loan which you take, but it will be kept in an account that you´ll have no access until the carnet & bike have returned home.

You get the carnet from the automobile association in your country, so if you plan to go to Pakistan & India, better contact them straight away. I dont think you can do those countries without it (Iran you maybe could, but it wont help much, because your biking-trip will end at the Pakistani border). Some have reported doing Pakistan without a carnet, but not riding, rather putting the bikes on trucks or trains, plus a huuuuuuuge hassle, that wouldnt really fit my idea of a motorbike-tour, or holiday.

I used a "Silk Road" map, sorry I dont remember the publisher and Ive already lost it. But it showed the area from around Ankara to Delhi, and was good enough for me, because I didnt take many side roads in East Turkey, Iran or Pakistan. It is a good idea to buy maps beforehand, for route planning, and also because sometimes it might be hard to find good ones on the road.