You can obtain a Chinese motorbike license using a US license. You will have to take a health check, register at the local police station and take a multiple choice test. You can take a mock test in english at this website using internet explorer.
If you do not have a foreign license then the procedure is much more complicated. You will need to join a driving school and take 2 practical tests in addition to the multiple choice theory test.
Plates to ride within the 2nd ring road will cost ~15,000RMB. There will undoubtedly be lots of queuing and red tape involved. It doesn’t matter what cc the bike is, unless it’s under 50! It’s the same procedure for both license and plates.