Cylinder, Piston and Piston Ring Inspection
Cylinder, Piston and Piston Ring InspectionCylinder
Visual inspection
Check cylinder walls for scratches, roughness or ridges which indicate excessive wear.
If cylinder wall is too rough, deeply scratched, ridged, replace cylinder block, piston rings and/or pistons.
Cylinder bore diameter, taper and out-of-round
Using cylinder gauge, measure cylinder bore in thrust and axial directions.
If any of the following conditions is noted, replace cylinder block.
^ 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:
If abnormality is found on cylinder inside wall, replace cylinder block.
NOTE:
There are two sizes for cylinder bore, to keep clearance between piston and cylinder properly.
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.
If abnormality is found, replace piston.
Piston diameter
As indicated in figure, piston diameter should be measured at specified position "a" 11.4 mm (0.449 in) from piston skirt end in the direction perpendicular to piston pin.
If measured diameter is less than its limit, replace piston.
New piston diameter standard size 91.990 - 92.020 mm
Piston diameter limit size
Piston clearance
Measure cylinder bore diameter and piston diameter to find their difference called is piston clearance. Piston clearance should be within its standard value.
If it is out of its limit, replace piston.
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) Measure clearance between ring and ring land using thickness gauge (2). If clearance is out of limit, replace piston.
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 using thickness gauge (2).
If measured gap exceeds limit, replace piston ring.
NOTE:
Remove carbon deposit from and clean top of cylinder bore before inserting piston ring.
Piston ring end gap
