Checking The Piston Rings

CONNECTING RODS AND PISTONS

NOTE:                                                d. If out of specification, replace the piston and
Measure cylinder bore “C” by taking side-to-side        piston rings as a set.
and front-to-back measurements of the cylinder.      e. Calculate the piston-to-cylinder clearance
Then, find the average of the measurements.             with the following formula.
                                                      • Piston-to-cylinder clearance =
           Bore                                         Cylinder bore “C” -
            79.000–79.010 mm (3.1102–                   Piston skirt diameter “D”
            3.1106 in)
           Taper limit                                           Piston-to-cylinder clearance
            0.050 mm (0.0020 in)                                  0.020–0.045 mm (0.0008–0.0018
           Out of round limit                                     in)
            0.050 mm (0.0020 in)                                 Limit
                                                                  0.12 mm (0.0047 in)
“C” = maximum of D1–D6
                                                     f. If out of specification, rebore or replace the
“T” = maximum of D1 or D2 - maximum of D5
                                                        cylinder, and replace the piston and piston
or D6                                                   rings as a set.
“R” = maximum of D1, D3 or D5 - minimum of           ▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
D2, D4 or D6                                         EAS24430

                                                     CHECKING THE PISTON RINGS
                                                     1. Measure:
                                                      • Piston ring side clearance
                                                        Out of specification → Replace the piston
                                                        and piston rings as a set.
                                                     NOTE:
                                                     Before measuring the piston ring side clearance,
                                                     eliminate any carbon deposits from the piston
                                                     ring grooves and piston rings.

b. If out of specification, rebore or replace the               Piston ring
   cylinder, and replace the piston and piston                   Top ring
   rings as a set.                                                 Ring side clearance
c. Measure piston skirt diameter “D” “a” with the                   0.030–0.070 mm (0.0012–
   micrometer.                                                      0.0028 in)
                                                                   Limit
         Piston                                                     0.120 mm (0.0047 in)
          Diameter D                                             2nd ring
            78.965–78.980 mm (3.1089–                              Ring side clearance
            3.1094 in)                                              0.020–0.060 mm (0.0008–
                                                                    0.0024 in)
                                                                   Limit
                                                                    0.120 mm (0.0047 in)

 b. 5 mm (0.20 in) from the bottom edge of the
    piston

                                                 5-106