Starter Motor Refurb

[PhilM]

Although I've now had my 1937 two seater (not Opal) project at home for several weeks now, I'm still in the process of getting the garage space sorted out in order to start work on the major items. I have a large double garage but the A7 shares the space with the Midget, a lathe and a small Mill so space is at a premium. This probably means that anything like engine out or body off chassis work is now going to have to wait till the spring when I can bear to put the Midget outside under a decent cover.

However being an impatient sort I've started to remove bite sized bits and pieces which can be overhauled and refurbished on the bench, the latest of which is the starter motor.  
On disassembly of the motor I found a bit of a mess, everything is covered in what looks like thick copper grease, which I guess is dust from commutator / brushes. 





I would guess that this stuff is quite conductive so I'd like to remove as much of it as is possible.
Is there something I can safely wash the area around the field coils out with?
I'm reluctant to use any strong solvents in case it adversely affects the insulation.

Any observations will be gladly received.

Many thanks,    .... Phil.