Cylinder Honing and Boring
1. Cylinder wall flex hone should be used for deglazing whenever piston(s) or ring set(s) require replacement and cylinder bores are found within specifications. Refer to step 7 for finish honing procedures.
2. If one or more cylinder bore(s) are damaged or exceed out of round specifications, cylinder honing and/or boring will be required. It is good practice to obtain the piston(s) before re-working a cylinder bore. Select oversize piston. Oversize Piston Diameters Available:
- 0.125 mm (0.005 inch)
- 0.400 mm (0.0157 inch)
NOTE: The cylinder bore diameter is determined by measuring at two axis (transverse and longitudinal) 63.5 mm (2 1/2 inch) from top of block and averaging them together.
3. Calculate amount to hone or bore cylinder.
a. Using a micrometer, measure the piston diameter at a right angle to the piston pin hole center line, 5 mm (0.200 inch) from the bottom of the piston.
b. Calculate the amount each cylinder is to be honed or bored as follows. Size to be honed or bored = P + C - H. where P = piston diameter, C = piston clearance 0.006 mm (0.0002 inch) to 0.044 mm (0.0017 inch), and H = allowance for finish honing 0.050 mm (0.002 inch).
NOTE: Cylinder No. 4 is 0.01 mm (0.0004 inch) larger than No.'s 1, 2 and 3.
4. Bore or finish hone cylinders to the following calculated dimensions.
a. Piston/Bore O.S. Dimension: 0.125 mm (0.005 inch)
- Bore O.S. Dimension (Cylinder No. 1, 2, 3): 82.115-82.135 mm (3.2328-3.2336 inch). (Cylinder No. 4): 82.125-82.145 mm (3.2333-3.2340 inch).
- Piston O.S. Dimension: 82.091-82.109 mm (3.239-3.2326 inch).
NOTE: 0.125 mm (0.005 inch) oversize bores can be honed to size following steps 6 and 7 under honing.
b. Piston/Bore O.S. Dimension: 0.400 mm (0.016 inch)
- Bore O.S. Dimension: (Cylinder No. 1, 2, 3): 82.39-82.41 mm (3.2436-3.2444 inch). (Cylinder No. 4): 82.40-82.42 mm (3.2440-3.2448 inch).
- Piston O.S. Dimension: 82.381-82.399 mm (3.243-3.244 inch).
CAUTION: The cylinder bore, piston and ring set must be equivalent in oversize dimensions (.125 mm or .400 mm O.S.). An 0.400 mm (0.016 inch) oversize bore require boring prior to honing.
5. Follow the manufacturer's instructions and machine the cylinder bore to 0.038-0.062 mm (0.0015-0.0025 inch) less than the required finished dimension to allow for honing.
WARNING: Do not allow hone to come out of cylinder bore while it is turning. the stones could be released and cause injury.
6. Hone bores to within 0.005 mm (0.0002 inch) of desired size using 120-150 grit stones.
7. Finish hone to desired size by removing 0.005 mm (0.0002 inch) left in second step using 320 grit stones.
CAUTION: Make sure crankshaft pulley/damper keyway is at 3 or 9 o'clock position to prevent damage of crankshaft connecting rod journals during honing.
a. Hone the cylinder bore using a 10W-30 or 5W-30 weight motor oil and flex hone.
b. Make sure the flex hone is rotating upon entry and removal from cylinder bore.
CAUTION: The recommended speed of the flex hone is 150 - 200 rpm. Do not use air pressure driven or high-speed tools.
c. Use 60 strokes per minute. Honing time should be approximately 20 seconds or 20 strokes per cylinder to develop a 45-50° (included angle) honing cross-hatch. One "stroke" consists of a full downward and upward motion of the flex hone in the cylinder bore.
d. Thoroughly scrub cylinder bores after honing with a scrub brush, a strong solution of hot water and Tided powder laundry detergent (or equivalent). Thoroughly rinse with hot clean water (high-pressure, if available).
CAUTION: If the cylinder bores are not thoroughly cleaned, the residual grit from the honing stones will wear out the piston rings and cylinder bores extremely fast, resulting in oil consumption. Never use solvent to clean cylinder bores; it will only redistribute the grit on the cylinder walls; detergent and hot water will carry the grit away.
e. Dry the cylinder bores and wipe them with a clean white towel saturated with engine oil. Dark residual grit on the towel after wiping the cylinder bore indicates the bores are not dean. The cleaning process in step e must be repeated until the towel is free of all dark residual grit.