Hi All: when I remove the starter & reinstall it, is there a chance I could dislodge the sprocket in the chain & have it drop. Is the sprocket tight in the chain or just sitting loose waiting for me to make my move? It seems easy to do, but the sprocket worries me a bit. Going to replace brushes & clean it up. How long do brushes last, any idea? It,s an 82, I,m the 2nd owner for 18 years And never had it off. Thanks Les.