Piston: Testing and Inspection

1. Using a bore gauge, measure cylinder bore for wear, out-of-round and taper. The standard inner diameter "Db" is 89.000 - 89.030 mm (3.5039 - 3.5051 inch). The wear limit is 0.2 mm (0.008 inch). Out-of-round (X - Y) is less than 0.015 mm (0.0006 inch). Taper is (A - B or A - C) less than 0.01 mm (0.0004 inch). If it exceeds the limit, rebore all cylinders. Replace cylinder block if necessary.
2. Check for scratches and seizure. If seizure is found, hone it.





NOTE: If cylinder block or piston is replaced, match piston grade with grade number on cylinder block upper surface.

3. Measure the piston skirt diameter and refer to Specifications. The measuring point "a" (distance from the top) is 52 mm (2.05 inch).





4. Check that the piston-to-bore clearance is within specification. Piston-to-bore clearance "B" is 0.020 - 0.040 mm (0.0008 - 0.0016 inch).
5. Determine the piston oversize according to amount of cylinder wear. Oversize pistons are available for service.
6. Cylinder bore size is determined by adding piston-to-bore clearance to piston diameter "A". Rebored size calculation formula is D = A + B - C where, D is the bored diameter; A is the piston diameter as measured; B is the piston-to-bore clearance and C is the honing allowance 0.02 mm (0.0008 inch).
7. Install main bearing cap and tighten bolts to 46 - 56 Nm (34 - 41 ft. lbs.). This will prevent distortion of cylinder bores.
8. 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 inch) or so at a time.

9. Hone cylinders to obtain specified piston-to-bore clearance.
10. Measure finished cylinder bore for out-of-round and taper. Measurements should be done after cylinder bore cools down.