Small Engines (Lawn Mowers, etc.): electric starter Tecumseh 33329 for snowblower, wd 40, electric starter

Question
My starter will turn over and engage when NOT attached to the engine. It will not turn over and start the engine when attached.  Is this just a matter of replacing the brushes ?

Answer
Does the shaft turn by hand?

Do you have any experience repairing electric motors?  Personnally, I take them to a local shop in town.  These guys rebuild electric motors everyday and do it in half the time I can...plus they don't charge that much.

You may try spraying some WD-40 around the brush area and then GENTLY tapping the are with a small hammer or screwdriver...I've seen the brushes stick causing a similar problem.
Is your motor a 110 AC or a 12 DC motor?
Let me know.
Eric