Check the mica depth (A). If the mica is too high (B), undercut the mica with a hacksaw blade to the proper depth. Cut away all the mica (C) between the commutator segments. The undercut should not be too shallow, too narrow, or V-shaped (D).

Commutator Mica Depth
Standard (New):	0.50−0.80 mm (0.020−0.031 in.)
Service Limit:	0.2 mm (0.008 in.)