In ideal circumstance find a bolt a little longer than double the diameter of the piston. Make sure the head is larger than the I.D. of the wrist pin, but smaller than the hole through the piston. (In non ideal circumstances, like clearing case shapes, or covers as here, or other obstructions improvise as best you can using the same methods.)
Use a deep wall socket, piece of tube with a washer, or stacks of washers that are larger than the wrist pin being pulled. Push the bolt through the wrist pin, put the socket or other improvised device over the end, screw a nut on and crank it out. Make sure there is enough stroke to pull it all the way out, add pieces if not.
As always, heat and your favorite penetrating fluid never hurts.
