Jensen A540 turntable freewheel coupling

[maybelateron]

My Jensen A540 turntable chipper has an overrun/freewheel coupling so that when you turn off the engine the chipping flywheel continues to turn and slow down until stopped. I have not come across any other chippers with an overrun/freewheel before. Can anyone shed light on why Jensen fit this? Also, it is quite a while since I last changed the oil in the freewheel (due to low hours use, not neglect), that I cannot remember exactly what you do to drain the old oil out. I can't find anything online about it, does anybody have the answer? I seem to remember you have to position the freewheel correctly then undo some of the countersunk bolts on the front of it?