Cylinder Boring

NOTE:
- To rebore the cylinder to oversize, keep the specified clearance between the oversize piston and the bore.
Piston to cylinder wall clearance:
Standard Value; 0.02-0.04 mm (0.0008-0.0016 inch).
Out of roundness and taper of cylinder bore.
Maximum allowable; 0.02mm (0.0008 inch).
- Make sure that all pistons used are of the same oversize.
1st O.S. 0.25 mm (0.0098 inch)
2nd O.S. 0.50 mm (0.0197 inch)
3rd O.S. 0.75 mm (0.0296 inch)
4th O.S. 1.00 mm (0.0394 inch)
- The standard measurement of the piston outside diameter is taken at a level 12mm (0.47 inch) above the bottom of the piston skirt and across the thrust faces.

NOTE: Size mark is stamped on top of the piston.

1. Measure the outside diameter of the piston to be used.
2. Based on the measured O.D., calculate the boring finish dimension. Boring finish dimension equals Piston O.D plus Piston To Cylinder Wall Clearance standard value.

NOTE: Leave sufficient material to finish hone to size.

3. Bore each of the cylinders to the calculated size.

CAUTION: To prevent distortion that may result from temperature rise during honing, bore the cylinder holes in the firing order sequence.

4. Hone the cylinders, finishing them to the proper dimension (piston outside diameter plus piston to cylinder wall clearance standard value).
5. Check the clearance between the piston and cylinder.

NOTE: When boring the cylinders, finish all of the cylinders to the same oversize. Do not bore only one cylinder to an oversize.