Hello,

I have been with a guy riding with an Xr400 when I was in Mongolia. It is a really nice bike for such trip, As I remember that was his modifications:
- You should try to fit an acerbis 22l tank for extra range.
- Front sprokets with different number of tooth so you can change them depending on the kind of road.
- A nice bash plate.


Now concerning your budget, It depend on how much time you are planing to do the trip (stoping a lot?). But, I think 3 to 4 month, If you are really serious about camping and eating cheap food, 15 000 euro is definitely enough (hell I could do a rtw trip with that budget... well 3/4).

In regards to the road you have chosen. Keep in mind that the "carnet" will be costly for Iran and India. Furthermore, I see 2 big problems:
-Pakistan: The east and Karachi are really dangerous, I have relation with peoples working in NGOs in that country and some history are... disturbing, let just say that westerner avoid to go out in the region of Quetta and Karachi. The west is "less dangerous" (you should keep a low profile).
Now I know an other rider who went in Pakistan last year (from west to north) and at some point he had police escort, same for a couple in 4x4 (north to west). The french government give some nice advice on all the countries, you should read it (if you speak french): Pakistan - France-Diplomatie-Ministère des Affaires étrangères
-Burma and China are a no go by motorcycle in my book... well you can try China if you are very rich and are willing to be followed by a "guide" all the time... Maybe you should considering shipping your bike at one point? Other rider have taken the "stan road".