tph1

The difference is difficult to explain properly but the best way is grunt ... bit like having a lazy V8 that pulls from anywhere where as the OS is like a japanese bike engine .. .. awsome power but you have to wind it up.

The grunt comes into its own after snaps and rolls on uplines where as with the 91 fx you need to keep the engine wound up with the YS you just blip the throttle and power pulls you through!