Piston, Piston Ring, and Piston Pin

PISTON, PISTON RING, AND PISTON PIN





1. Measure the outer diameter of each piston at a right angle (90°) to the piston pin, 22.5 mm (0.89 in) below the oil ring land lower edge.

Piston diameter





2. Calculate the piston-to-cylinder clearance. Subtract the piston diameter from the cylinder bore of the corresponding cylinder.





Clearance: 0.030-0.043 mm (0.0012-0.0016 in)
Maximum: 0.10 mm (0.0039 in)

3. If the clearance exceeds the maximum, replace the piston or rebore the cylinders to fit oversize pistons.
4. If the piston is replaced, the piston rings must also be replaced.





5. Measure the piston ring-to-ring land clearance around the entire circumference using a new piston ring.

Clearance
Top: 0.035-0.065 mm (0.0014-0.0025 in)
Second: 0.030-0.065 mm (0.0012-0.0025 in)
Oil: 0.07-0.16 mm (0.0030.006 in)
Maximum: 0.15 mm (0.006 in)

6. If the clearance exceeds the maximum, replace the piston and piston ring.





7. Insert the piston ring into the cylinder by hand and use the piston to push it to the bottom of the ring travel.
8. Measure each piston ring end gap with a feeler gauge. Replace the piston ring if necessary.

End gap
Top: 0.15-0.30 mm (0.006-0.011 in)
Second: 0.25-0.40 mm (0.010-0.015 in)
Oil rail: 0.20-0.70 mm (0.008-0.027 in)
Maximum: 1.0 mm (0.039 in)





9. Measure each piston pin hole diameter in X and Y directions at the four points (A, B, C, and D) as shown.

Diameter: 19.988-20.000 mm (0.7870-0.7874 in)





10. Measure each piston pin diameter in X and Y directions at the four points (A, B, C, and D) as shown.

Diameter: 19.974-19.980 mm (0.7864-0.7866 in)

11. Calculate the piston pin-to-piston pin bore clearance.

Clearance: 0.008-0.026 mm (0.0004-0.0010 in)

12. If the clearance exceeds specification, replace the piston and/or piston pin.