16918-ZY3-003 Honda O-RING (Honda Code 6990451).

Illustration 1 g00845975
Typical example
(1) The chamber that is on the top of the piston must face the right side of the engine. (2) The Shibaura name that is on the inside of the piston must align with the stamped number on the connecting rod.Piston and Piston Rings
Illustration 2 g00845969
Typical example
Use a feeler gauge to measure the clearance between the piston ring groove and the piston ring. If the clearance is greater than the service limit, use a new piston ring and check the clearance.If the clearance is within the service limit, renew the piston rings. If the clearance is outside of the service limit, renew the piston. (1) Top piston ringShape of top ring (A)Naturally aspirated ... Barrel faceC0.5 and C0.7Clearance between piston ring groove and top piston ring ... 0.06 to 0.10 mm (0.0024 to 0.0039 inch)Service limit for clearance of top piston ring ... 0.25 mm (0.0098 inch)Gap of top piston ring ... 0.13 to 0.28 mm (0.0051 to 0.0110 inch)Service limit for gap of top piston ring ... 1.0 mm (0.039 inch)Note: Install the word "T" or "RN" toward the top of the piston. New top piston rings have a red identification mark. The red identification mark must be on the left of the ring gap when the top piston ring is installed on an upright piston.Note: The top surface of the piston ring should be equally distant from the top face of the cylinder block at all points before the piston ring end gap is measured with a feeler gauge. (2) Intermediate ringShape of intermediate ring (B) ... TaperC0.5 and C0.7Clearance between piston ring groove and intermediate ring ... 0.05 to 0.09 mm (0.0020 to 0.0035 inch)Service limit for clearance of intermediate ring ... 0.25 mm (0.0098 inch)Gap of intermediate ring ... 0.10 to 0.25 mm (0.0039 to 0.0098 inch)Service limit for gap of intermediate ring ... 1.0 mm (0.039 inch)Note: Install the word "T" or "RN" toward the top of the piston. New intermediate rings have a green identification mark. The green identification mark must be on the left of the ring gap when the intermediate ring is installed on an upright piston.Note: The top surface of the piston ring should be equally distant from the top face of the cylinder block at all points before the piston ring end gap is measured with a feeler gauge. (3) Oil control ringC0.5 and C0.7Clearance between piston ring groove and oil control ring ... 0.02 to 0.06 mm (0.0008 to 0.0024 inch)Service limit for clearance of oil control ring ... 0.15 mm (0.0059 inch)Gap of oil control ring ... 0.10 to 0.30 mm (0.0039 to 0.0118 inch)Service limit for gap of oil control ring ... 1.0 mm (0.039 inch)The oil control ring has two components. The two components of the oil control ring are installed in the following order.
Spring (D)
Oil control ring (C)Note: A latch pin is used to hold both ends of the spring of the oil control ring in position. The ends of the spring of the oil control ring must be 180 degrees opposite the end gap of the oil control ring.Note: The top surface of the piston ring should be equally distant from the top face of the cylinder block at all points before the piston ring end gap is measured with a feeler gauge. (4) PistonC0.5 and C0.7Diameter of the piston skirt ... 66.9375 to 66.9525 mm (2.6353 to 2.6359 inch)Service limit ... 66.7 mm (2.6260 inch)Clearance of the piston skirt to the cylinder wall ... 0.048 to 0.082 mm (0.0019 to 0.0032 inch)Service limit ... 0.25 mm (0.010 inch)Diameter of the piston pin ... 18.998 to 19.002 mm (0.7480 to 0.7481 inch)Service limit ... 18.98 mm (0.7472 inch)Clearance between the hole for the piston pin and the piston pin ... 0 to +0.008 mm (0 to +0.0003 inch)Service limit ... 0.02 mm (0.0008 inch)Refer to Specifications, "Cylinder Head" for the piston height for a given gasket thickness.