Three-time National champion Jimmy Weinert
(wearing a Kawasaki - naturally - lime green windbreaker), but piloting a SUZUKI (!) pit bike. #3...

See other image in this gallery of #3 Rich Thorwaldson on a Suzuki.
Weinert's way of saying that he's "riding" Thorwaldson, in his own inimitable way.
Ahhhh, politics comes to motocross.

See: http://home.ama-cycle.org/forms/museum/hofbiopage.asp?id=292