Probably saw this in the 80's. A commercial started out with a straight on shot of a Porsche 911 at the starting line of a race track. As the car accelerated (driving straight forward, toward the viewer) a voice-over stated that the Porsche 911 was the fastest production car in the world, and continued to give statistics on the speed of the car. After a few seconds, a motorcycle leans out from behind the car and proceeds to pass it. The announcer starts telling the stats for the bike. The final line of the commercial: "How fast is the [name of motorcycle]? Ask the guy in the Porsche."
I've been trying to identify the make of the motorcycle and can't find anything.