In maintenance, if the clearance between the piston pin and the connecting rod bushing is too large, or when the piston and the piston pin are replaced, the connecting rod bushing must be replaced to ensure its normal coordination. Connecting rod bushing and connecting rod small head hole should have an appropriate amount of interference to prevent bushing rotation or axial movement when working. The new bushing can be pressed into the connecting rod head with a bench clamp. Some engine connecting rod bushings have no machining allowance and do not need to be repaired after pressing. For bushings with processing allowance, after pressing the connecting rod head, the following repairs should be made:
(1) Reaming or enameling the connecting rod bushing, pay attention to controlling the processing allowance, so as to avoid reaming or enameling the bushing hole.
(2) Put the piston pin into the bushing for grinding. The piston pin is clamped with a bench clamp, and a small amount of lubricating oil is injected into the piston pin and bushing to rotate the connecting rod and move it forward and backward along the axis of the piston pin. The piston pin can stay in the bushing hole until the connecting rod is at a 75 degree angle to the horizontal plane. When the connecting rod is tapped, the piston pin slowly drops in the bushing hole and ends.
(3) After grinding, the fit clearance between piston pin and connecting rod bushing should be 0.004-0.010 mm, and the contact area between piston pin and bushing should be more than 75%.