Piston and Connecting Rod

PISTON AND CONNECTING ROD ASSY DISASSEMBLY
1. CHECK FIT BETWEEN PISTON AND PISTON PIN
Try to move the piston back and forth on the piston pin. If any movement is felt, replace the piston and pin as a set.

2. REMOVE PISTON RINGS
(a) Using a piston ring expander, remove the two compression rings.

(b) Remove the two side rails and oil ring expander by hand.

HINT: Arrange the rings in correct order only.

3. DISCONNECT CONNECTING ROD FROM PISTON
(a) Using a small screwdriver, pry off the snap ring from the piston.

(b) Gradually heat the piston to approx. 60°C (1 400 F.

HINT: The piston and pin are a matched set. Arrange the pistons, pins, rings, connecting rods and bearings in correct order.

PISTON AND CONNECTING ROD INSPECTION
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.

2. INSPECT PISTON
A. Inspect piston oil clearance

HINT: There are three sizes of the standard diameter, marked "1", "2" and "3,, accordingly. The mark is stamped on the top of the piston.

(a) Using a micrometer, measure the piston diameter at right angles to the piston pin center line. 26 mm (1.02 in.) from the piston head.
Piston diameter:
STD:
Mark "1" 87.360 - 87.370 mm (3.4394 - 3.4398 in.)
Mark "2" 87.370 - 87.380 mm (3.4398 - 3.4402 in.)
Mark "3" 87.380 - 87.390 mm (3.4402 - 3.4405 in.)
0/S 0.50 87.410 - 87.440 mm (3.4413 - 3.4425 in.)
(b) Measure the cylinder bore diameter in the thrust directions.
(c) Subtract the piston diameter measurement from the cylinder bore diameter measurement.
Standard oil clearance: 0.13 - 0.15 mm (0.0051 - 0.0059 in.)
Maximum oil clearance: 0.17 mm (0.0067 in.)
If the oil clearance is greater than maximum, replace all the six pistons. If necessary, rebore all the six cylinders or replace the cylinder block.

HINT: (Use new cylinder block): Use a piston with the same number mark as the standard bore diameter marked on the cylinder block.

B. Inspect piston ring groove clearance
Using a thickness gauge, measure the clearance between new piston ring and the wall of the piston ring groove.
Ring groove clearance:
No.1: 0.010 - 0.080 mm (0.0004 - 0.0031 in.)
No.2: 0.030 - 0.070 mm (0.0012 - 0.0028 in.)
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 bottom of the ring travel, 1OO mm (3.94 in.from the top of the cylinder block.

(c) Using a thickness gauge, measure the ring end gap.
Standard ring end gap:
No.1: 0.280 - 0.500 mm (0.0110 - 0.0197 in.)
No.2: 0.380 - 0.600 mm (0.0150 - 0.0236 in.)
Oil (Side rail): 0.150 - 0.570 mm (0.0059 - 0.0224 in.)
Maximum ring end gap:
No.1: 1.10 mm (0.0433 in.)
No.2: 1.20 mm (0.0472 in.)
Oil (Side rail): 1.17 mm (0.0461 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 six 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 a rod aligner and thickness gauge, check the connecting rod alignment.
Check for bend.
Maximum bend: 0.05 mm (0.0020 in.) per 100 mm (3.94 in.)
If bend is greater than maximum, replace the connecting rod assembly.

Check for twist.
Maximum twist: 0.15 mm (0.0059 in.) per 100 mm (3.94 in.)
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 - 22.014 mm (0.8663 - 0.8667 in.)
(b) Using a micrometer, measure the piston pin diameter.
Piston pin diameter: 21.997 - 22.006 mm (0.8660 - 0.8664 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.

(d) Using a pin hone 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.

D. Inspect connecting rod bolts
(a) Install the cap nut to the connecting rod bolt. Check that the cap nut can be turned easily by hand to the end of the thread.

(b) If the cap nut cannot be turned easily, measure the outer diameter of the compressed thread with a vernier caliper.
Standard outer diameter: 7.860 - 8.000 mm (0.3094 - 0.3150 in.)
Minimum outer diameter: 7.60 mm (0.2992 in.)

HINT: If the location of this area cannot be judged by visual inspection, measure the outer diameter at the location shown in the illustration.

If the outer diameter is less than minimum, replace the connecting rod and cap nut as a set.

BORING OF CYLINDER

HINT: Bore all the six cylinders for the oversized piston outside diameter. Replace the piston rings with ones to match the oversized pistons.
1. KEEP OVERSIZED PISTONS
Oversized piston diameter:
0/S 0.50: 87.945 - 87.975 mm (3.4624 - 3.4636 in.)

2. CALCULATE AMOUNT TO BORE CYLINDER
(a) Using a micrometer, measure the piston diameter at right angles to the piston pin center line, 26 mm (1.02 in.) from the piston head.
(b) Calculate the amount each cylinder is to be rebored as follows:
Size to be rebored P + C - H
P = Piston diameter
C = Piston oil clearance 0.13 - 0.15 mm (0.0051 - 0.0059 in.)
H = Allowance for honing 0.02 mm (0.0008 in.) or less
3. BORE AND HONE CYLINDERS TO CALCULATED DIMENSIONS
Maximum honing: 0.02 mm (0.0008 in.)
NOTICE: Excess honing will destroy the finished roundness.