If you've ever wondered the answer to the question in the title you need to visit How Many Left?. Unless it's a very old car or bike or a kit car you can find how many are left on the road and see the last 10 years of history. I was reminded of the website by the name of a forum member who's name implied he had a certain motorcycle. There are only 174 such bikes still in use from what was a very popular bike. I have an Italjet dragster 180 of which there are only 56 with a similar number of 125s and only 19 50s. There are plenty of old motors where only one is left still in use. Have fun exploring!