The crap on the internet written by people to get any attention blows out of all proportions, especially in this here forum.
Large displacement bikes were never really banned nation-wide, only certain cities / municipalities / provinces / counties stopped issuing new license plates and registration for large displacement bikes (i.e. Chang-Jiang sidecars).
During the boom of the 1990's and 2000's every village idiot and foreign looking english teacher was seen riding a CJ sidecar with a Beijing black "A" plate around capital city, even embassies and country representative offices had them CJ's with special black / red embassy plates, them CJ's were really fashionable and brought out a whole new breed of scam artists (bike shops).

Yes, in the late 90's and the years afterwards quite a lot of "grey imported" large displacement motorbikes were confiscated in bigger cities and municipalities like Shanghai, Beijing, Shenzhen, Guangzhou, Tianjin, Zhuhai, Xiamen, etc. to resurface in the hinterland provinces up for sale with new dodgy documents and ridden back to the big cities mention earlier.
The notorious second hand markets in the Guangzhou / Beijing suburbs and the Tianjin outskirts spring to mind right now and the fake HD shops around Beijing, the custom bike builders ("wreckers") between Beijing and Tianjin....

One clever and smart move by the Shanghai government was the free exchange of motorcycle plates (yellow plates above 125cc displacement) for car plates as everyone knows cars have more status (face matter) compared to the two wheeled motorbikes. The Shanghai city government laughed as tens of thousands of motorcycle owners exchanged plates for the more prestigious car plates and they got the motorbikes of the roads and boosted new car sales. Obviously the pool of available motorcycle license plates decreased drastically and the prices for rego / plates (motorbikes) went up as new ones were not issued for quite a very long time.

Just a gentle reminder, same goes for the motorbikes on expressways China laws and regulations, never been really revised since the early 1990's and till today motorcycles technically are allowed on expressways nationwide but every county / municipality / province makes up rules and regulations as they dream them up.

Ride safe! PAL