to my knowledge, the BMW bike dealer in Beijing cannot rent motorcycles, they trying to but as always in China: Red Tape! they have heavy difficulties getting registration / license / insurance for rental bikes and looks like there is still a long way to go until this issue is sorted. furthermore, Shg/BJ authorities does not issue temporary motorcycle license to individuals.
even you were able to rent a bike in Beijing, there is still the grey area about travelling to or through other Mainland China provinces, they implemented a "interprovince travel ban for motorcycles" three years ago. you can get away with it being a foreigner but they could give you hassles and confisctate the bike. ain't life in China great?!
doubt very much that you can enter China easily with an Mongolian plate (registration).
honest, if your talking about a CJ= Chang-Jiang 750cc sidecar, personally would not do a long haul trip on a CJ sidecar, you will not enjoy it. you need some repair knowlegde about the old CJ beast and furthermore they are unconfortable, slow,heavy and too many breakdowns, trust me - driving CJ's since 1989 in China....
[This message has been edited by butchman (edited 06 July 2004).]
Somewhere down the road in China…. life is one lap with no restarts and the finish line is unknown ~ keep going!!! TBR-China