On Sun, 03 Jun 2012 10:40:07 -0700, Jeff Liebermann
wrote:

Only one brush? It should be sparking equally under both brushes. Are
the brushes curved to fit the commutator shape? Is one brush
different? Are the commutator sections pitted? Are the brush faces
pitted? Are they the correct size and tupe of brushes?

Add to the above list, are the brush springs sufficiently strong?

Your idea of seating the brushes is my idea of burning away the
carbon and spraying the debris all over the inside of the engine. Find
a round file with approximately the same diameter as the commutator
and file the brushes.

2nd thought, a file might be a bit too aggressive for the small
brushes. Find a wooden dowel of approximately the same diameter as
the commutator, wrap a piece of very find sandpaper around the dowel,
and use that to pre-curve the brush faces.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558