When i hit the starter & the pinon gear engages it will not spin the flywheel. Sometimes it does, but it is not consistent. Had the starter apart & all the gears look good. The clutch in there turns hard. I sprayed it with teflon oil & that helped. Checked the battery[new] & its fine, 12.8 volts. Do not have a load tester. Any help would be appreciated. Jon M Riley
End play in the armature, the drive engages too far and contacts the ring. It is a simple fix to shim the drive end of the armature to keep it from hitting the ring.
Check for a voltage drop between the battery and starter connection.. a bad or weak ground could cause the problems also... The battery could be new and check good but if there is a weak connection there is a lack of cranking juice getting to the starter it will effect it's operation.