Lubricate the following parts with oil before mounting: the piston pin, the piston, the cylinder and the big-end bearing.
Couple the piston with the connecting rod, thus the combustion chamber centre B is perpendicularly under end A of the nozzle housed inside the head.
Lubricate the piston pin and insert it in the piston, lightly pressing with your thumb.
Make sure that the two stop rings are well housed inside their seats.
A = Clearance volume
B = Head gasket
The thickness B head gasket determines the clearance volume A which shall be 0.75 ÷ 0.90 mm for 3LD 450, 3LD 451/S, 3LD 510, 3LD 510/S and 0.80 ÷ 1.00 mm for 4LD 640, 4LD 705, 4LD 820.
Measure the piston crown position as to the cylinder surface and chose a gasket having a suitable thickness.
Always consider that the piston at the top dead centre could be at the same level, either under or over the cylinder.