You're looking at two different bikes (I picked this up from the IMDB):
"The motorcycles used by Kevin Dillon in the film are a 500cc T100R Triumph Tiger and a 200cc T20 Triumph Tiger Cub for the jumps."
In the main photo, it's the 500cc bike, same with the first image in nocar's message. The bike doing the donut is the smaller machine. You can see the cub has a rigid rear suspension and the engine itself is less massive.