Cylinder Block Assembly
Cylinder^ Inspect cylinder walls for scratches, roughness, or ridges, which indicate excessive wear. If cylinder bore is very rough or deeply scratched, or ridged, rebore cylinder and use over size piston.
^ Using a cylinder gauge, measure cylinder bore in thrust and axial directions at 2 positions (1, 2) as shown in the figure. If any of the following conditions is noted, rebore cylinder.
- Cylinder bore dia. exceeds limit.
- Difference of measurements at 2 positions exceeds taper limit.
- Difference between thrust and axial measurements exceeds out-of-round limit.
Cylinder bore dia. limit: 84.050 mm (3.3090 inch)
Taper and out-of-round limit: 0.10 mm (0.004 inch)
NOTE: If any one of four cylinders has to be rebored, rebore all four to the same next oversize. This is necessary for the sake of uniformity and balance.
Pistons
^ Inspect piston for faults, cracks or other damages. Damaged or faulty piston should be replaced.
^ Piston diameter:
As shown in the figure, piston diameter should be measured at a position 26.5 mm (1.04 inch) (1) from piston skirt end in the direction perpendicular to piston pin.
Piston diameter:
^ Piston clearance:
Measure cylinder bore diameter and piston diameter to find their difference, which is piston clearance. Piston clearance should be within specification as given below. If it is out of specification, rebore cylinder and use oversize piston.
Piston clearance: 0.02 - 0.04 mm (0.0008 - 0.0015 inch)
NOTE: Cylinder bore diameters used here are measured in thrust direction at 2 positions.
^ Ring groove clearance:
Before checking, piston grooves must be clean, dry and free of carbon deposits.
Fit new piston ring (1) into piston groove, and measure clearance between ring and ring land by using thickness gauge (2). If clearance is out of specification, replace piston.
Ring groove clearance
Top: 0.03 - 0.07 mm (0.0012 - 0.0027 inch)
2nd: 0.02 - 0.06 mm (0.0008 - 0.0023 inch)
Piston Pin
^ Check piston pin, connecting rod small end bore and piston bore for wear or damage, paying particular attention to condition of small end bore bush. If pin, connecting rod small end bore or piston bore is badly worn or damaged, replace pin, connecting rod or piston.
^ Check piston pin clearance in small end. Replace connecting rod if its small end is badly worn or damaged or if measured clearance exceeds limit.
Piston clearance in small end:
Standard: 0.003 - 0.014 mm (0.0001 - 0.0005 inch)
Small-end bore: 21.003 - 21.011 mm (0.8269 - 0.8272 inch)
Piston pin dia.: 20.997 - 21.000 mm (0.8267 - 0.8268 inch)
Piston Rings
To measure end gap, insert piston ring into cylinder bore and then measure the gap by using thickness gauge.
If measured gap is out of specification, replace ring.
NOTE: Clean carbon deposits and any other dirt from top of cylinder bore before inserting piston ring.
Piston ring end gap:
Connecting Rod
^ Big-end side clearance:
Check big-end of connecting rod for side clearance, with rod fitted and connected to its crank pin in the normal manner. If measured clearance is found to exceed its limit, replace connecting rod.
Big-end side clearance
Standard: 0.25 - 0.40 mm (0.0099 - 0.0157 inch)
Limit: 0.45 mm (0.0177 inch)
^ Connecting rod alignment:
Mount connecting rod on aligner to check it for bow and twist. If limit is exceeded, replace it.
Connecting rod alignment
Limit on bow: 0.05 mm (0.0020 inch)
Limit on twist: 0.10 mm (0.0039 inch)
Crank Pin and Connecting Rod Bearings
^ Inspect crank pin for uneven wear or damage. Measure crank pin for out-of-round or taper with a micrometer. If crank pin is damaged, or out-of round or taper is out of limit, replace crankshaft or regrind crank pin.
Crank Pin diameter:
Crank shaft out-of-round limit ("A" - "B") and taper limit ("a"-"b"): 0.01 mm (0.0004 inch)
^ Rod bearing:
Inspect bearing shells for signs of fusion, pitting, burn or flaking and observe contact pattern. Bearing shells found in defective condition must be replaced.
2 kinds of rod bearing are available; standard size bearing and 0.25 mm (0.0098 inch) undersize bearing. For identification of undersize bearing, it is painted red (1) at the position as shown in the figure, undersize bearing thickness is 1.605 - 1.615 mm (0.0632 - 0.0635 inch) at the center of it.
^ Rod bearing clearance:
1. Before checking bearing clearance, clean bearing and crank pin.
2. Install bearing in connecting rod and bearing cap.
3. Place a piece of gaging plastic (1) to full width of crank pin as contacted by bearing (parallel to crankshaft), avoiding oil hole.
4. Install rod bearing cap to connecting rod.
When installing cap, be sure to point arrow mark (1) on cap to crankshaft pulley side, as shown in the figure. After applying engine oil to rod bolts, tighten cap nuts to specified torque.
Tightening torque
Connecting rod bearing cap nut (a): 45 Nm (4.5 kg-m, 33.0 ft. lbs.)
NOTE: DO NOT turn crankshaft with gaging plastic installed.
5. Remove cap and using a scale (2) on gaging plastic (1) envelope, measure gaging plastic (1) width at the widest point (clearance).
If clearance exceeds its limit, use a new standard size bearing and remeasure clearance.
Connecting rod bearing clearance:
Standard: 0.039 - 0.057 mm (0.0016 - 0.0022 inch)
Limit: 0.08 mm (0.0031 inch)
6. If clearance can not be brought to within its limit even by using a new standard size bearing, replace crankshaft or regrind crank pin to undersize as follows.
^ Install 0.25 mm undersize bearing to connecting rod big-end.
^ Measure bore diameter of connecting rod big-end.
^ Regrind crank pin to following finished diameter
^ Confirm that bearing clearance is within above standard value.
Crankshaft
Crankshaft runout
Using a dial gauge, measure runout at center journal. Rotate crankshaft slowly. If runout exceeds its limit, replace crankshaft.
Crankshaft runout:
Limit: 0.06 mm (0.0023 inch)
Crankshaft thrust play
Measure this play with crankshaft set in cylinder block in the normal manner, that is, with thrust bearing and journal bearing caps installed. Tighten crankcase bolts to specified torque in such order (1 -> 22) as shown in the figure.
Tightening torque
Thrust and journal bearing cap bolt (8 mm thread diameter) (a): 60 Nm (6.0 kg-m, 43.5 ft. lbs.)
Thrust and journal bearing cap bolt (10 mm thread diameter) (b): 27 Nm (2.7 kg-m, 19.5 ft. lbs.)
Use a dial gauge to read displacement in axial (thrust) direction of crankshaft. If its limit is exceeded, replace thrust bearing with new standard one or oversize one to obtain standard thrust play.
Crankshaft Thrust Play
Standard: 0.10 - 0.35 mm (0.0039 - 0.0138 inch)
Limit: 0.42 mm (0.0165 inch)
Thickness of crankshaft thrust bearing:
Standard: 2.500 mm (0.984 inch)
Oversize (0.125 mm (0.0049 inch)): 2,563 mm (0.1009 inch)
Out-of-round and taper (uneven wear) of journals
An unevenly worn crankshaft journal shows up as a difference in diameter at a cross section or along its length (or both). This difference, if any, is determined by taking micrometer readings. If any one of journals is badly damaged or if amount of uneven wear in the sense explained above exceeds its limit, regrind or replace crankshaft.
Limit on out-of-round (A - B) and taper (a - b): 0.01 mm (0.0004 inch)
Main Bearings
General information
^ Service main bearings are available in standard size and 0.25 mm (0.0098 inch) undersize, and each of them has 5 kinds of bearings differing in tolerance.
^ Upper half of bearing (1) has oil groove (2) as shown in the figure.
Install this half with oil groove to cylinder block.
^ Lower half of bearing does not have oil groove.
Visual inspection
Check bearings for pitting, scratches, wear or damage. If any malcondition is found, replace both upper and lower halves. Never replace either half without replacing the other half.
Main bearing clearance
Check clearance by using gaging plastic (1) according to the following procedure.
1. Remove lower crankcase.
2. Clean bearings and main journals.
3. Place a piece of gaging plastic the full width of bearing (parallel to crankshaft) on journal, avoiding oil hole.
4. Install lower crankcase to cylinder block. Tighten crankcase bolts, following sequence in the figure. Tighten crankcase bolts to specified torque.
Tightening torque
Thrust and journal bearing cap bolt (8 mm thread diameter) (a): 60 Nm (6.0 kg-m, 43.5 ft. lbs.)
Thrust and journal bearing cap bolt (10 mm thread diameter) (b): 27 Nm (2.7 kg-m, 19.5 ft. lbs.)
NOTE: Do not rotate crankshaft while gaging plastic is installed.
5. Remove lower crankcase and using scale (2) on gaging plastic (1) envelop, measure gaging plastic (1) width at its widest point. If clearance exceeds its limit, replace bearing. Always replace both upper and lower inserts as a unit. A new standard bearing may produce proper clearance. If not, it will be necessary to regrind crankshaft journal for use of 0.25 mm undersize bearing. After selecting new bearing, recheck clearance.
Main Bearing Clearance
Standard: 0.032 - 0.052 mm (0.0013 - 0.0020 inch)
Limit: 0.060 mm (0.0023 inch)
Selection of main bearings
^ STANDARD BEARING:
If bearing is in malcondition, or bearing clearance is out of specification, select a new standard bearing according to the following procedure and install it.
1. First check journal diameter. As shown in the figure, crank web No. 2 has stamped numbers.
3 kinds of numbers ("1", "2" and "3") represent the following journal diameters.
Stamped numbers on crank web No. 2 represent journal diameters marked with an arrow in the figure respectively.
For example, stamped number "1" indicates that corresponding journal diameter is 57.994 - 58.000 mm.
Journal diameter:
2. Next, check crankcase (bearing cap) bore diameter without bearing. On lower crankcase five alphabets are stamped as shown in the figure.
3 kinds of alphabets ("A", "B" and "C") represent the following cap bore diameters.
Stamped alphabets on lower crankcase represent crankcase bore diameter marked with an arrow in the figure respectively.
For example, stamped alphabet "A" at bearing cap No. 2 indicates that bearing cap bore diameter of bearing cap No. 2 is 62.000 - 62.006 mm.
Main bearing cap bore diameter (for bearing cap No. 1, No. 2, No. 3 and No. 5):
Main bearing cap bore diameter (for bearing cap No. 4):
3. There are 5 kinds of standard bearings differing in thickness. To distinguish them, they are painted in the following colors at the position as shown in the figure.
Each color indicated the following thickness at the center of bearing.
Standard size main bearing thickness:
4. From number stamped on crank web No. 2 and alphabets stamped on lower crankcase, determine new standard bearing to be installed to journal.
For example, if number stamped on crank web No. 2 is "1" and alphabet stamped on lower crankcase is "B", install a new standard bearing painted in "Black" to its journal.
New standard size bearing specification:
5. Using gaging plastic (1) and scale (2), check bearing clearance with newly selected standard bearing.
If clearance still exceeds its limit, use next thicker bearing and recheck clearance.
6. When replacing crankshaft or cylinder block and lower crankcase due to any reason, select new standard bearings to be installed by referring to number stamped on new crankshaft or alphabets stamped on new lower crankcase.
^ UNDERSIZE BEARING (0.25 mm):
0.25 mm undersize bearing is available, in 5 kinds varying in thickness.
To distinguish them, each bearing is painted in the following colors at such position as shown in the figure.
Each color represents the following thickness at the center of bearing.
Undersize main bearing thickness
^ If necessary, regrind crankshaft journal and select undersize bearing to use with it as follows.
1. Regrind journal to the following finished diameter.
Finished Journal diameter: 57.732 - 57.750 mm (2.2729 - 2.2736 inch)
2. Using micrometer, measure reground journal diameter. Measurement should be taken in 2 directions perpendicular to each other in order to check for out-of-round.
3. Using journal diameter measured above and alphabets stamped on lower crankcase, select an undersize bearing. Check bearing clearance with newly selected undersize bearing.
Undersize bearing specification:
Flywheel
^ If ring gear is damaged, cracked or worn, replace flywheel.
^ If the surface contacting clutch disc is damaged, or excessively worn, replace flywheel.
^ Check flywheel for face runout with a dial gauge. If runout exceeds its limit, replace flywheel.
Flywheel runout:
Limit: 0.2 mm (0.0078 inch)
Cylinder Block
^ Distortion of gasketed surface Using straightedge (1) and thickness gauge (2), check gasketed surface for distortion and, if flatness exceeds its limit, correct it.
Gasketed Surface Flatness
Limit: 0.06 mm (0.0024 inch)
^ Honing or reboring cylinders
1. When any cylinder needs reboring, all other cylinders must also be rebored at the same time.
2. Select oversized piston according to amount of cylinder wear.
Oversize piston specification:
3. Using micrometer, measure piston diameter.
4. Calculate cylinder bore diameter to be rebored as follows.
D = A + B - C
D: Cylinder bore diameter to be rebored.
A: Piston diameter as measured.
B: Piston clearance = 0.02 - 0.04 mm (0.0008 - 0.0015 inch)
C: Allowance for honing = 0.02 mm (0.0008 inch)
5. Rebore and hone cylinder to calculated dimension.
NOTE: Before reboring, install lower crankcase and tighten to specification to avoid distortion of bearing bores.
6. Measure piston clearance after honing.