Via a bridge, the Nürburgring Nordschleife track crosses a street of the town Adenau/Breidscheid. When you drive downhill "Wehrseifen" just before climbing up to "Ex-Mühle", look over the wall, you can see some buildings on the right hand side. There you find the motorcycle mural.
Unfortunately, in real life the mural disappeared due to a new window of the house.