Way back in the days of slot cars, we used to buy bottles of some magic elixer into which we would immerse a new motor, and then run it at low speed for a while.  The brushes wore in, not out, and the fluid carried the worn material away.  The result was way improved brush/commutator fit and a motor that was squeekey clean inside.

Anyone know what the stuff was, and where to get it?

I have a couple of applications where a brushed motor will be just fine, and I want them to last!

I used to race 1/10 scale Electric RC cars during the 80's and we also used distilled water for "running in brushes". Another popular "mod" was to chamfer the edges of the brush face where it met the commutator apparently to reduce the breakup of the brushes as they passed over the slots between the segments. "Timing" brushes (On fixed can motors used in "standard" classes) by stepping the brush to advance it's relative position was another trick.

TTFN
John.

A couple of drops of dishwashing liquid in normal water and run the motor in that at full speed for a few minutes. Keep checking the brushes to see when they are bed nicely to the commutator.

Then a drop of brasso (brass or silver polish liquid) on each bush run again for a minute, this time not in the water, make sure to then submerge the motor back in the water soap mixture to wash out the brasso in the bushes. Lube the bushes again with some thin oil when finished as most the bushes are an oil lite bush and absorbs oil to keep the bush lubricated.

I have been doing that for years and normally increase the RPM by 1500 under no load and the amp draw goes down.

Lionel