Apply engine oil to new О-rings and install it onto the oil jet.
Install the oil jet into the crankcase properly as shown (jet hole side facing toward the connecting rod side).
Apply engine oil to the piston pin outer surface.
Set the piston over the connecting rod with the piston direction and position properly as noted during removal.
Place a clean shop towel over the crankcase to prevent the clip from falling into the crankcase.
Install new piston pin clips.
Make sure the piston pin clips are seated properly and their end gaps are not aligned with the cutouts in the piston.