The secondary should float a little. The theroy of once lined up , always lined up , doesn't work. Your motor twist on the mounts as you put power to it, the clutch will float, even while under power, to help to minimize the misalighnment caused by the engine torque. The clutch will move in and out on the shaft because it is turning and not in a static position when the pressure is on it. !/4" each way is far too much and will wear the keyway out rather fast. 1/8 to a max of 3/16" The M series have different style motor mounts to try to help eliminate the changing alighnment problem, but they still have more belt problems than the floating secondary.