lash cap safty
larger surface area on a skinny valve stem, that's whats on a hi flow small block chev head with ultra high lift cam, also helps keep the keepers from flying out as easy during valve float.
On these 212cc industrial type engines with there cheese soft valve springs its probably cheap insurance in the event that someone accidentally over revs the motor and floats the valves before the governor can pull it back (broken drive chain or belt for example). If the valves are floated and the piston hits the slow in closing exhaust valve the dogged in retainer can separate from the valve and it will drop. The lash cap and retainer are fitted pieces that need a lot of room to become separated, acts like an additional interlock.
They don't put one on the intake cause it's not in danger of being hit by the piston during valve float.