I am really interested in any ones reponse to this.
As i want to travel from vietnam to mongolia and im not sure how to achieve this.

Beijing customs bike import situation
 

So, just to update anyone who's interested:

I thought I'd just give it a go, and after a day of arguments I didn't understand in various Moscow offices, managed to get the bike on the train (Moscow - Beijing, about 250 GBP for 200kg). Too late to get it on the same train as me, it followed my arrival in Beijing by a couple of days.

The good news was: the bike made it through - I saw it with my own eyes in one brief, glorious moment. The bad news was: Beijing customs would not let me have it. Apparently they are not legally authorised to import motor vehicles. Also no luck via a customs broker.

Worth a try though. They are letting me keep the bike in storage until I can get the right documents to convince another branch of Chinese customs to authorise the import. Then I will ride to Tibet. Maybe.

Please keep us informed of your proceedings!

I would love to know how you go, even if you have to but your bike back on the train and train out of the country!