The engine stopped while running it. I took it apart and insured the front two set of wheels had no binding, relubricated them. Removed the motor cleaned all the grease out relubricated that .. also,insured that there was no binding in that set of wheels. I removed all the linkages except the side rods and the binding is still there when I manually turn the motors flywheel. The wheels always bind in the same position. Again, it seems as though the holes in the side rod may have become too large and there is too much playin them for the front free wheeling wheels to not bind. They just don't maintain the same position as the back to set of wheels. Thank you for trying to help with this problem.