I am curious and am fairly sure I know the answer to this question, but after reading up on some of the laws published it states...

Article 16 No units or individuals shall do the following:

　　(1) assembling motor vehicles or altering the registered composition, structure or features of motor vehicles without authorization;

　　(2) changing the models of motor vehicles, their engine number, chassis number or the identification code of the vehicles;

So, am I led to believe that once a bike has been licensed I must rebuild the same motor should it fail in order to retain the engine number? Or does an authorized service shop have the ability to replace the motor with say..one that is better of the same cc? Of course the owner says its not a problem, but....

I ask because I have found a decent used bike, but the motor is shot (cracked case). I don't mind dropping in a new one but not if its going to cause ANY issues with registration or future inspections.