QUOTE (Gary @ 23 Oct 2007, 16:37)
<{POST_SNAPBACK}>Is there any downside?
From the electrical side, it's all benefit. Higher magnetic flux means more torque from lower current, better protection against burning out motor coils.
Mechanically, if the bearings are in good condition then no problem. If the bearings are worn then the motor may become very noisy as the armature is dragged off centre by the higher field. This effect is worst in three pole motors which do not fill the magnetic gap between the pole pieces very well. If the bearings are worn enough it is sometimes possible to see the armature 'snapping' across the pole pieces, six times a revolution, as the motor is slowly hand turned.