I had this same problem. You should have a tube for the pushrod, make sure that its not 'pinched' tight between the tank and the fuse wall, or anything else. Also, make sure that the pushrod has a strait path to the nosegear (servo and pushrod exit are on the same side of the fuse insted of). I used some airgun cleaning oil on mine to loose'n it up a bit. If you are using the smaller diamiter pushrods, you may want to try a bigger one.

Once you get it, it wont take much to turn the plane... very little is needed.

Hope this helped out a little.