(a) Using a small screwdriver, pry out the two snap rings.
(b) Gradually heat the piston to 80 - 90°C (176 -194 °F).
(c) Using plastic-faced hammer and brass bar, lightly tap out the piston pin and remove the connecting rod.
• The piston and pin are a matched set.
• Arrange the pistons, pins, rings, connecting rods and bearings in correct order.
INSPECTION OF PISTON AND CONNECTING ROD ASSEMBLIES
1. CLEAN PISTON
(a) Using a gasket scraper, remove the carbon from the piston top.
(b) Using a groove cleaning tool or broken ring, clean the piston ring grooves.
(c) Using solvent and a brush, thoroughly clean the piston.
NOTICE: Do not use a wire brush.
2. INSPECT PISTON A. Inspect piston oil clearance
HINT: There are three sizes of the standard piston diameter, marked "1 ", "2" and "3" accordingly. The mark is stamped on the piston top. (a) Using a micrometer, measure the piston diameter at right angles to the piston pin center line, 23.5 mm (0.925 in.) from the piston head. Piston diameter:
EHUU t wjm
(b) Measure the cylinder bore diameter in the thrust direc tions.
(See step 4 on page EM-286)
(c) Subtract the piston diameter measurement from the cylinder bore diameter measurement. Standard oil clearance: 0.079 - 0.099 mm (0.0031 - 0.0039 in.)
Maximum oil clearance: 0.119 mm (0.0047 in.)
If the oil clearance is greater than maximum, replace all the four pistons and rebore all the four cylinders. If necessary, replace the cylinder block. HINT (Use new cylinder block): Use a piston with the same number mark as the cylinder bore diameter marked on the cylinder block.
EHUU t wjm
B. Inspect piston ring groove clearance
Using a feeler gauge, measure the clearance between new piston ring and the wall of the piston ring groove. Ring groove clearance: 0.030 - 0.070 mm (0. 0012 - 0.0028 i n . )
If the clearance is greater than maximum, replace the piston.
C. Inspect piston ring end gap
(a) Insert the piston ring into the cylinder bore.
(b) Using a piston, push the piston ring a little beyond the bot tom of the ring travel, 115 mm (4.53 in.) from the top of the cylinder block.
(c) Using a feeler gauge, measure the end gap. Standard end gap: N o .1 0.270 - 0.500 m m (0.0106 - 0.0197 in.) N o . 2 0.350 - 0.600 m m (0. 0138 - 0.0234 in.) Oil (Side rail) 0.200 - 0.550 mm (0-0079 - 0.0217 in.) Maximum end gap: No.1 1.10 mm (0.0433 in.) No.2 1.20 mm (0.0472 in.) Oil (Side rail) 1.15 mm (0.0453 in.) If the end gap is greater than maximum, replace the piston ring. If the end gap is greater than maximum, even with a new piston ring, rebore all the four cylinders or replace the cylinder block.
D. Inspect piston pin fit
At 60°C (140° F), you should be able to push the piston pin into the piston pin hole with your thumb.
3. INSPECT CONNECTING ROD A. Inspect connecting rod alignment
Using rod aligner and feeler gauge, check the connecting rod alignment.
• Check for bending. Maximum bending:
If bend is greater than maximum, replace the connecting rod assembly.
• Check for twist. Maximum twist:
If twist is greater than maximum, replace the connecting rod assembly.
B. Inspect piston pin oil clearance
(a) Using a caliper gauge, measure the inside diameter of the connecting rod bushing.
Bushing inside diameter: 22.005 - 22.017 mm (0.8663 - 0.8668 in.)
(b) Using a micrometer, measure the piston pin diameter. Piston pin diameter: 21.997 - 22.009 mm (0.8660 - 0.8665 in.)
(c) Subtract the piston pin diameter measurement from the bushing inside diameter measurement. Standard oil clearance: 0.005 - 0.011 mm (0.0002 - 0.0004 in.)
Maximum oil clearance: 0.05 mm (0.0020 in.)
If the oil clearance is greater than maximum, replace the bushing. If necessary, replace the piston and piston pin as a set.
C. If necessary, replace connecting rod bushing
(a) Using SST and a press, press out the bushing. SST 09222-30010
(b) Align the oil holes of a new bushing and the connecting rod.
(c) Using SST and a press, press in the bushing.
(d) Using a pin hole grinder, hone the bushing to obtain the standard specified clearance (see step B above) between the bushing and piston pin.
(e) Check the piston pin fit at normal room temperature. Coat the piston pin with engine oil, and push it into the connecting rod with your thumb.
Was this article helpful?