I dont know the whole science may be some engineer who designed this engine can give a exact info who they damp vibration of engine in RP..
But all I can tell you is that RP has Different valves, Different crank, different cam, has autoadjustable screw heads on tappets with extra steal cushion which rotates its face automatically according to vales postion some thing very unque to RP ... different gear box and bulky frame which eats most of the vibration which might come from engine..