I'm not sure what you're asking Dave, nor where you're located (the US vs abroad), but in the state of Pennsylvania, the frame VIN is used to register the motorcycle for license plates and that VIN must match the title. There is no requirement for the engine serial number to match the frame vin serial. If you don't have a title, then you'll need to look up your localities process for applying for a title of ownership prior to registering. This process can often be difficult and time consuming and sometimes impossible to accomplish.