Connecting Rod: Testing and Inspection
PISTON AND CONNECTING ROD INSPECTION1. 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 ring grooves.
(c) Using a soft brush and solvent, thoroughly clean the piston.
CAUTION: Do not damage the piston.
2. Inspect piston.
A. Inspect Piston Oil Clearance.
NOTE: There are 3 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 mm (0.91 inch) from the piston head.
Piston diameter:
Mark "1": 73.900 - 73.910 mm (2.9O94 - 2.3098 inch)
Mark "2": 73.910 - 73.920 mm (2.9098 - 2.9120 inch)
Mark "3": 73.920 - 73.930 mm (2.9120 - 2.9106 inch)
(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: 0.09 - 0.11 mm (0.0035 - 0.0043 inch)
Maximum oil clearance: 0.13 mm (0.0051 inch)
If the oil clearance is greater than maximum, replace all 4 pistons. If necessary, replace the cylinder block.
NOTE: (Use new cylinder block: Use a piston with the same number mark as the cylinder bore diameter marked on the cylinder block.
B. Inspect Piston Ring Groove Clearance.
Using a feeler gauge, measure the clearance between new piston ring and the wall of the ring groove.
Ring groove clearance:
No. 1: 0.04 - 0.08 mm (0.0016 - 0.0031 inch)
No. 2: 0.03 - 0.07 mm (0.0012 - 0.0028 inch)
If the oil 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, 110 mm (4.33 inch) from the top of the cylinder block.
(c) Using a feeler gauge, measure the end gap.
Standard end gap:
No. 1: 0.26 - 0.48 mm (0.0102 - 0.0189 inch)
No. 2: 0.36 - 0.57 mm (0.0142 - 0.0224 inch)
Oil (Side rail): 0.13 - 0.50 mm (0.0051 - 0.0197 inch)
Maximum end gap:
No. 1: 1.07 mm (0.0421 inch)
No. 2: 1.02 mm (0.0402 inch)
Oil (Side rail): 1.10 mm (0.0433 inch)
If the end gap is greater than maximum, replace the piston ring. If necessary, replace the cylinder block.
3. Inspect connecting rods.
Using a rod aligner, check the connecting rod alignment.
^ Check for out-of-alignment.
Maximum out-of-alignment: 0.03 mm (0.0012 inch) per 100 mm (3.94 inch)
If out-of-alignment is greater than maximum, replace the connecting rod assembly.
^ Check for twist.
Maximum twist: 0.05 mm (0.0020 inch) per 100 mm (3.94 inch)
If twist is greater than maximum, replace the connecting rod assembly.
NOTE: If replacing the connection rods, replace the same number of connecting rod bearings as that of new connecting rod caps.