alan0899 and speedair have it. It's the washer. Easy to lose and a MANDATORY part. They call it a "thrust washer" item #10 on this drawing http://downloads.hobbico.com/evpl/osm/ev15460aa.pdf and Tower has them cheap http://www3.towerhobbies.com/cgi-bin...EARCH=46120000 Don't use a cheap substitute.