Lets start with the basics
The banshee is a 350
The YFZ450 is a 450
The Banshee is a 2 stroke
The YFZ450 is a 4 stroke
E1=Comparison Engine (450)
E2=Comparison Standard (350)
S1=Stroke Cycles of First Engine (4)
S2=Stroke Cycles of Second Engine (2)
The formula: (E1/E2) x (S2/S1) = Overall excitement and fun
You can also manipulate this equation algebraiclly, i.e., if you have your fun factor, and have the stroke cycles of 2 bikes, and the displacement of 1 bike, to find the approximate displacement of the second bike and so on.
So, (450/350) x (2/4)=.643