I have enjoyed the 6th International Yinchuan Car and Motorcycle Tourism Festival, I rode the 1299 km to there from Beijing with two groups of sidecar bike (Changjiang 750) riders through Inner Mongolia. About 3000 bikes were there (I was told and cannot verify the number), for the corso lining up according to one's Chinese Province. As bikes are hard to bring into China, "International" refers nowadays more to the presence of foreigners living in China. Police were helpful, but expressways are mostly out of reach for motorcyclists.
You can buy bikes in China for cash, many registrations are fake (especially from Hebei Province), some people ride in the West of China without number plates and drivers license, especially outside of the big cities. Generally speaking, the East and South East is more strict towards motorcyclists than the North and North East. Bif cities often ban all bikes or bikes from other cities and provinces, rural places have no bans on bikes, but few of them on foreigners. Especially Changjaings (three wheelers require a Chinese D license) are looked upon in a more lenient way. Remember that China has rules that are enforced, occasionally (then it can be your very very bad luck) or rarely enforced. Bike confiscation, bike theft can happen, probably even worse things in the case of accidents.