why does the over center spring have to be removed

new to the clutch workings. why when you put in a diaphram clutch does the over center spring have to be removed? they never took mine out and the pedal seems screwy.clutch seems to disengage when just over half way to floor then its stiff from that point to the floor, from a dead stop it seems to come back up real fast. is this from the spring still being in there??