Cylinder, Piston and Piston Ring Inspection
Cylinder, Piston and Piston Ring InspectionReference: Piston, Piston Ring and Connecting Rod Disassembly and Reassembly
Cylinder
Visual inspection
Check cylinder walls for scratches, roughness or ridges which indicate excessive wear.
Replace cylinder block, piston rings and/or pistons if cylinder wall is too rough, deeply scratched or ridged.
Cylinder bore diameter, taper and out-of-round
Use cylinder gauge to measure cylinder bore in thrust and axial direction. Replace cylinder block if any of the following conditions are discovered:
^ Cylinder bore exceeds limit.
^ Difference of measurements at two positions ([1] and [2]) exceeds taper limit.
^ Difference between thrust [4] and axial [3] measurements exceeds roundness limit.
CAUTION:
Replace cylinder block if any abnormality is found on cylinder inside wall.
NOTE:
There are two sizes for cylinder bore, to keep clearance between piston and cylinder properly.
To distinguish standard value, refer to Piston, Piston Ring and Connecting Rod Disassembly and Reassembly.
Cylinder bore diameter
Standard
Cylinder bore diameter
Limit: 92.050 mm (3.6240 in.)
Cylinder bore roundness ([3] - [4])
Limit: 0.020 mm (0.00078 in.)
Cylinder bore taper ([1] - [2])
Limit: 0.013 mm (0.00051 in.)
Piston
NOTE:
Two sizes of piston are available as standard size spare part so as to ensure proper piston-to-cylinder clearance.
Visual inspection
Inspect piston for cracks or other damages.
Replace piston if any abnormalities are found.
Piston diameter
As indicated in figure, piston diameter should be measured at specified position "a" 11.4 mm (0.448 in) from piston skirt end in the direction perpendicular to piston pin.
Replace piston if measured diameter is less than its limit.
New piston diameter standard size
Piston diameter limit size
Piston clearance
Measure cylinder bore diameter and piston diameter to find their difference called piston clearance. Piston clearance should be within its standard value.
Replace piston if it is out of limit.
NOTE:
Cylinder bore diameters used here are measured in thrust direction at two positions.
Piston clearance
Limit: 0.12 mm (0.0047 in.)
Ring groove clearance
1) Before checking, piston grooves must be clean, dry and free from carbon deposits.
2) Fit new piston ring (1) into piston groove.
3) Use feeler gauge (2) to measure clearance between ring and ring land.
Replace piston if clearance is out of limit.
Ring groove clearance
Piston Ring
Piston ring end gap
To measure end gap, insert piston ring (1) into cylinder bore, and then measure the gap with feeler gauge (2).
Replace piston ring if measured gap exceeds limit.
NOTE:
Remove carbon deposit from top of cylinder bore before inserting piston ring.
Piston ring end gap
