Update:
I took the 2009 FISE blade motor apart tonight, easily. Just remove the two bolts, then gently pry the top off with two screw drivers. The top has the brush setup attached. Then pull out the armature / commutator out. It was full of brush dust. It needs a good cleaning ! The bearings still rotate smoothly, so that is good news, but the bushes are very worn.
The brush assemble (not sure what to call this plastic part) is pryed easily from the top housing, then the white plastic spring reatiners are pryed off to remove the springs and brushes.
Next step for me is to get the new brushes and it looks like they can be soldered to the copper wire or cut off and the new ones crimped.
The commutator has some wear, but I believe I can polish it with abrasive cloth.
I received this motor early summer in 2009 and due to a dying battery only mowed the back yard in 2010. Based on this observation, the brushes MUST be replaced at least every season, IMO. I would not push it past one season. It might even be worth putting in new brushes before cutting the heavy lush grass in the spring, then replace them again during the slow growth part of the summer to be ready for early fall.
Next project is to inspect the wheel motors. Good news is the planetary gear setup does not seem to have much backlash after running for a season and a half. I will take the apart and clean and grease them. Not sure about brush replacement on these IMS motors.
