This is my favorite for gear driven cam sounds.. VFR750 Honda
[ame="http://www.youtube.com/watch?v=K68881TWCT4&feature=related"]YouTube - VFR 750 RC 36 MIG[/ame]
They sound something like a cross between a Nascar stocker and a Viper on the road.
[ame="http://www.youtube.com/watch?v=iU4B5QUnVHM&feature=related"]YouTube - Honda VFR RC36 Sound III[/ame]