It's Jay Leno's favorite motorcycle: the classic English superbike known as the Vincent Black Shadow.

More than 50 years after the last one rolled off the line, the Black Shadow is still an incredible piece
of mechanics and design.

From the article written by Jay Leno:
...and the fastest motorcycle was the Vincent Black Shadow. Vincent ads read:
"The World's Fastest ­Standard Motorcycle. This is a Fact Not a Slogan."

http://www.popularmechanics.com/cars/a6962/vincent-black-shadow-the-first-superbike-and-maybe-the-best/
.
.