I'm having problems with my Optimum BF20L Motor as it's making arking noises which gets worse the faster I run it.
I had been doing some heavy machining and the motor got very hot on a few occations.
I actually broke the sacuficial gear and after replacing this I noticed the brushers where sparking a far bit over 2500rpm.
I cleaned the armiture tried it again but soon after the problem started again.
Pulled the motor off and this time measured between the windings and found a couple that where 5K ohm and not 0.6 ohm as the other where.
I noticed that winding attached to the copper pad through a small crimp block which a tapped down with a miniture hammer and it made a better connection of 0.6 ohm.
Thinking I solved the motor problem I put it all back together but she is still sparking like a fire cracker and making missing sounds when running at high speeds.
The brushes are about half worn and look OK to me.
I can buy a new motor for AU$210 but what to eliminate everything first.