You mean the pulley wheel housing cover? Yeah sounds like what gadget is saying. The bolt that holds the pulley wheel onto the valve itself is protruding too far and the cover is holding it still. You'll be able to see if there are marks on the inside of the cover. Give me a shout if you find you have the wrong one in and i can send you the right one with the right washers on. Make sure you're cables arent too tight. Follow the set up instructions perfectly or you could burn the motor in your servo unit out.
