Taking apart a starter engine – brushes

I replaced my starter several years ago with a overhauled one and my old starter has been awaiting overhauling. This is what you get if you take the starter apart. The starter is powered by a solenoid which closes the circuit of the electro motor and connects the cogwheel to the flywheel of the engine. On my old starter it was the solenoid which was dirty so that the circuit could not be closed.