From Germany to Mongolia by motorcyle

[sim11]

Hello. I´m 22 years old and am an active person. Me and some friends of mine are planning to make one of our´s biggest adventures ever. We´ll be driving from Berlin to Mongolia! First of all, what bike do you prefer? I will buy one later this year, cuz we are leaving in June 2017. I wanna get to know my bike as well. We will be driving on both good roads, but also off-road, dirt roads and so on. This vehicle are to tolerate these bad conditions including bad weather, bad air, mountains, different airpressure. Also, it has to be between 500-700 cc and under 94 hp like medium heavy motorbike. Of course, we´ll drive all day long, so it has to tolerate to drive long. So, which bike do you recommend?
Edit: we will be driving through Russia, visit Moskva and continue the journey along the southern part of Russia! There will be bad and good roads though, but any tips for where to drive? which highroad man? What should we explore?

Our plan is going from Norway to Berlin, from Berlin to Moskva, from Moskva to Astana, and from Astana to Ulaanbataar (Mongolia). But which exact roads do you recommend?