A valve drive mechanism includes a tappet assembly (24) which comprises a centre tappet (43), a pair of side tappets (41, 42) between which the centre tappet (43) is interposed so as to move relatively to the side tappets (41, 42), and a locking/unlocking ...

Intake valve drive shaft and exhaust valve drive shaft (2,15) are arranged in parallel to each other and provided with sprockets, respectively, for receiving engine rotation from a crank shaft. A rocker cam (13) is swingably mounted on the intake valve dri...