There are two brushes inside that wear out. I get replacements from the hardware store and just solder in a new pair then spray the starter down with electrical cleaner on the inside and off it goes again. Sounds easier then it really is, you need four hands to get it back together again but I manage so most anyone should be able to do it. A new starter from Hobby People is about 20 bucks so if you have problems getting it back together you know where to go.