Dan
Guest
Jim, The back is normally OK but I have found some early '80's machines that had flange for holding up right side of rear door to be mislocated. It would have to be cut out and then rewelded with rear of concave true to cylinder. The cylinder or concave is not adjustable to move for or aft to correct the clearance. We let the cylinder down to zero clearance and then reach threw round side inspection doors or climb on top of raddle chain to feel the clearance between bar and concave. It should be very close to rubbing or rubbing on both sides. If in corn and soybeans only it would maybe be OK to have more clearance as long as it is close to the same side to side for you would normally be running larger cylinder clearances than the hard to knock out crops. I'm sure the way the factory intends them to be is rubbing on the back and just clearing on the front when at zero clearance. As you open up the clearance the front gap will increase faster than the rear so there will be a wedge effect. The channel bars that are fastened in front of concave could be though of as part of the concave with filler bars installed. The front channel bar will have a gap even when cylinder is at zero and that is where the wedgeing starts. Hope that helps you out. Dan