I'm using the same servo that you are and I don't have any trouble. Mine will retract all the way. Make sure that the servo moves the wire going to the bellcrank the same distance that it takes to extend and retract the servo. I operate the servo without the wires tightened to see how far the easy connectors travel. Then I mark the wire (masking tapes works good) and operate the gear by hand to see it the travles match up. If not then you have to move the easy connectors or use a different servo arm. You should be able to make it work if you get the travel set right. Good Luck. I also used the stock wheels that came with the kit. Sam