Have a brushfull motor making a clanking grinding sound of death? It's likely one of the brushes have come out of the their tracks and needs to be reset.
You'll likely find that these motors are easy to take apart, and terribly difficult to put together - requiring custom tools and a little coaxing.
Step 1: Take Apart Motor
Remove any case screws and set aside - then pull the back cover away from the motor housing. If your brushes are spring loaded (like this motor's), they may spring apart. Remove the casing slowly to prevent any rogue springs from disappearing under your work bench.
Step 2: Inspection
Look at the motor's innards. Look for physical damage, scorching etc. If you don't find anything, look for free fragments of anything. The case magnets should not touch anything except the motor housing.
If everything looks good, take a look at the brushes. They should have a concave portion on one end where they touch the motor armature.
If everything looks good, we'll hope that the brushes just need to be reset.
Step 3: Custom Tools
Push the spring and brush assembly into it's holder.
- use a small screwdriver to push the spring into the holder (there's a channel on the side for this)
- push the brush into the holder while holding the spring back
- insert a bent paper clip through the small hole
Step 4: Assemble Motor
Now it's time to complete assembly.
Lower the motor housing onto the paperclipped rear casing. Be sure the tightening screws line up.
Now, pull the paper clips out of the housing. The brushes should gently push up against the armature (you shouldn't here loud clicking or similar).
Screw your motor back together and make sure the shaft spins freely.
Now test. The first time I gave it power, my leads had a rather large spark. The second time it powered on without problem :)