A valve train for operating a cylinder valve assembly for an internal combustion engine comprising: - a main event motion source configured to provide main event valve motions to the valve assembly, - a main rocker arm, arranged to swivel on a corresponding rocker shaft and operatively connected to the main event motion source, in such a way to assume an active condition at main event and a released condition otherwise, - a valve bridge including a casing wherein is slidably inserted - a lost motion assembly, wherein the lost motion assembly includes an outer plunger having a longitudinal development arranged to receive a main rocker arm action and to transmit such action to the valve bridge through a locking element, wherein the locking element is arranged to assume - a locking condition with a first portion disposed in a corresponding seat of the valve assembly and a second portion disposed in a passing through opening of the outer plunger, - an unlocking condition where the locking element is completely outside the seat of the valve assembly, wherein, said outer plunger includes an axial cavity where an inner plunger is suitable to slide under in response of oil pressurization, wherein said oil pressurization transmitted by the rocker arm, and wherein said inner plunger includes a recess suitable to accommodate said locking element during oil pressurization such that to define said unlocking condition; the lost motion assembly being configured to define a clearance between a bottom portion of the casing and a bottom portion of the outer plunger configured to receive said pressurized oil and wherein said casing is provided of a passing through opening to discharge said pressurized oil in such a way to dump a sudden restriction of the clearance; the train being characterized in that the bottom portion of the outer plunger is provided of a tapered pin affixed to penetrate the passing through opening at least in a predetermined operating condition. - a main event motion source configured to provide main event valve motions to the valve assembly, - a main rocker arm, arranged to swivel on a corresponding rocker shaft and operatively connected to the main event motion source, in such a way to assume an active condition at main event and a released condition otherwise, - a valve bridge including a casing wherein is slidably inserted - a lost motion assembly, wherein the lost motion assembly includes an outer plunger having a longitudinal development arranged to receive a main rocker arm action and to transmit such action to the valve bridge through a locking element, wherein the locking element is arranged to assume - a locking condition with a first portion disposed in a corresponding seat of the valve assembly and a second portion disposed in a passing through opening of the outer plunger, - an unlocking condition where the locking element is completely outside the seat of the valve assembly, wherein, said outer plunger includes an axial cavity where an inner plunger is suitable to slide under in response of oil pressurization, wherein said oil pressurization transmitted by the rocker arm, and wherein said inner plunger includes a recess suitable to accommodate said locking element during oil pressurization such that to define said unlocking condition; the lost motion assembly being configured to define a clearance between a bottom portion of the casing and a bottom portion of the outer plunger configured to receive said pressurized oil and wherein said casing is provided of a passing through opening to discharge said pressurized oil in such a way to dump a sudden restriction of the clearance; the train being characterized in that the bottom portion of the outer plunger is provided of a tapered pin affixed to penetrate the passing through opening at least in a predetermined operating condition.