Piston To Cylinder Bore Clearance
Cylinder Bore Inner Diameter
- Using bore gauge, measure cylinder bore for wear, out-of-round and taper at six different points on each cylinder. (X" and "Y) directions at (A", (B) and (C) (X" is in longitudinal direction of engine.
Standard inner diameter:
95.500 - 95.530 mm (3.7598 - 3.7610 in)
Out-of-round (Difference between (X) and (Y)):
0.015 mm (0.0006 in)
Taper limit (Difference between (A) and (C)):
0.01 mm (0.0004 in)
- If the measured value exceeds the limit, or if there are scratches and/or scuff marks on the cylinder inner wall, hone or re-bore the inner wall.
Piston Skirt Diameter
Measure the outer diameter of piston skirt with micrometer.
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Measure point |
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: Distance from the top 43.03 mm (1.6941 in) |
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Standard |
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: 95.480 - 95.510 mm (3.7590 - 3.7602 in) |
Piston to Cylinder Bore Clearance
Calculate by piston skirt diameter and cylinder bore inner diameter (direction "X", position "B").
(Clearance) = (Cylinder bore inner diameter) - (Piston skirt diameter).
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Standard |
: 0.010 - 0.030 mm (0.0004 - 0.0012 in) |
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Limit |
: 0.08 mm (0.0031 in) |
- If the calculated value exceeds the limit, replace piston and piston pin assembly. Refer to How to Select Piston and Bearing .
Re-boring Cylinder Bore
- Cylinder bore size is determined by adding piston to cylinder bore clearance to piston skirt diameter.
Re-bored size calculation: D = A + B - C
where,
D: Bored diameter
A: Piston skirt diameter as measured
B: Piston to cylinder bore clearance (standard value)
C: Honing allowance 0.02 mm (0.0008 in)
- Install lower cylinder block, and tighten to the specified torque. Otherwise, cylinder bores may be distorted in final assembly.
- Cut cylinder bores.NOTE:
- When any cylinder needs boring, all other cylinders must also be bored.
- Do not cut too much out of cylinder bore at a time. Cut only 0.05 mm (0.0020 in) or so in diameter at a time.
- Hone cylinders to obtain the specified piston to cylinder bore clearance.
- Measure the finished cylinder bore for out-of-round and taper.NOTE: Measurement should be done after cylinder bore cools down.