I am looking to buy a used Harley in the next couple of months. Unfortunately I don't know a lot about them, British bikes being my thing. My aim is to get a machine with about 20,000 kms on it. But what is considered low miles for a Harley engine? Which is the better engine the Evolution or the Twin Cam? What sort of mileage could I expect to get out of an engine before a re build is required? 

thanks, Nilo