Cylinder Boring

1. Oversize pistons used should be determined based on the largest bore cylinder.
Size Identification Mark
0.25 0.25 (0.010) O.S
0.50 0.50 (0.020) O.S
0.75 0.75 (0.030) O.S
1.00 1.00 (0.039) O.S

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

2. Measure the outside diameter of the piston to be used.
3. Based on the measured O.D., calculate the boring finish dimension.
Boring finish dimension:
Piston O.D + 0.02 to 0.04 mm (0.0008 to 0.0016 inch) (clearance between piston and cylinder) - 0.02 mm (0.008 inch) (honing margin.)
4. 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.

5. Hone the cylinders, finishing them to the proper dimension (piston outside diameter + gap with cylinder).
Piston-to-cylinder wall clearance:
0.01-0.03 mm (0.0004-0.0012 inch)
6. 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.