0384549 JOHNSON BASE PLATE ASSEMBLY

When handling the piston assembly, be aware that the piston pin plug which fits on the end of the piston pin, is only used to prevent the piston pin from scuffing the cylinders. It does not retain the pin in the assembly, once the piston assembly is removed from the cylinder, the pin is free to fall out of the assembly at any time.
(1) Crater. The piston is a symmetrical piston with an "on center" crater. Thoroughly lubricate piston group 360 degrees in zone (A) with clean engine oil prior to inserting into the block group.(2) Top piston ring. Install ring with side marked "UP-1" toward top of piston. Clearance between ends of piston ring when installed in a cylinder liner with a bore size of 125.000 mm (4.9213 in) ... 0.625 0.190 mm (.0250 .0075 in)Increase in clearance between ends of piston ring for each 0.03 mm (.001 in) increase in cylinder liner bore size ... 0.09 mm (.004 in)Minimum depth of groove in piston for top ring (new) ... 5.43 mm (.214 in)(3) Intermediate piston ring. Install ring with side marked "UP-2" toward top of piston. Width of groove in piston for intermediate ring (new) ... 3.061 0.013 mm (.1205 .0005 in)Minimum depth of groove in piston for intermediate ring (new) ... 5.43 mm (.214 in)Thickness of intermediate ring (new) ... 2.988 .013 mm (.1176 .0005 in)Clearance between groove and intermediate ring (new) ... 0.047 to 0.099 mm (.0019 to .0039 in)Clearance between ends of piston ring when installed in a cylinder liner with a bore size of 125.000 mm (4.9213 in) ... 0.625 0.125 mm (.0250 .0050 in)Increase in clearance between ends of piston ring for each 0.03 mm (.001 in) increase in cylinder liner bore size ... 0.09 mm (.004 in)(4) Oil regulating piston ring. Oil ring spring ends to be assembled 180 degrees from ring end gap (orange colored portion of spring must be visible at ring end gap).Width of groove in piston for oil ring (new) ... 4.033 0.013 mm (.1588 .0005 in)Minimum depth of groove in piston for oil ring (new) ... 3.727 mm (.1467 in)Thickness of oil ring (new) ... 3.987 0.013 mm (.1570 .0005 in)Clearance between groove and oil ring (new) ... 0.020 to 0.072 mm (.0008 to .0028 in)Clearance between ends of piston ring when installed in a cylinder liner with a bore size of 125.000 mm (4.9213 in) ... 0.44 0.15 mm (.017 .006 in)Increase in clearance between ends of piston ring for each 0.03 mm (.001 in) increase in cylinder liner bore size ... 0.09 mm (.004 in)After piston rings have been installed, rotate rings so the end gaps are 120 degrees apart.(5) Crown assembly.(6) Piston pin bore diameter in piston skirt ... 50.815 .005 mm (2.0006 .0002 in)Piston pin bore diameter in piston crown assembly ... 50.830 0.008 mm (2.0012 .0003 in)Thoroughly lubricate piston pin with clean engine oil prior to inserting into piston group and rod assembly.(7) Piston skirt.