The little end bearing needs to be as accurate as possible, we do not want the bush to be loose in the connecting rod as it means this will wear. If the gudgeon pin is very loose in the bush it will cause hammering to occur. It the gudgeon pin is tight in the bush the hardened steel pin will be forced to rotate in the piston, this means the piston is likely to wear.

  1. Remove the old bush (a hydraulic press may be required), check the con rod little end eye for ovality and measure the diameter.
  2. Measure the diameter of the gudgeon pin at the widest point (obviously the little end must be able to pass over this).
  3. Select a suitable piece of phosphor bronze and secure in the three-jaw chuck of the lathe.
  4. Start by machining out the centre to fit the gudgeon pin.
  5. Machine the OD to fit the con rod including extra diameter for the press fit.
  6. Machine the end face
  7. Slightly chamfer the OD to end face edge to guide the press fit.
  8. Bore out the oil groove with the special tool (if still around) or make a tool for it)
  9. Part off the bush over-lengthed
  10. Secure the bush in the three jaw chuck such that you can machine the second end face.
  11. Machine the bush to length, it should end up slightly proud of either side of the con rod.
  12. Mount the bush in the machine vice of the pillar drill being sure not to damage the surface finish of the OD or make the bush oval.
  13. Drill the hole for the oil to flow through, being careful not to let the drill snag.
  14. Remove the burrs from the oil groove and hole (the flutes of a drill are ideal for this), being careful not to damage any other surfaces.
  15. File the slot for directing the oil into the little end.
  16. Press the bush into the con rod making sure the alignment is correct as you should not move it once it is pressed in.
  17. Make sure the gudgeon pin still fits (this fit will have contracted by a fraction of a thou as a result of the press fit).