
B: SERVICE DATA
NOTE:
STD: Standard, I.D.: Inner Diameter, O.D.: Outer Diameter, OS: Oversize, US: Undersize
Belt ten-
sion
adjusterProtrusion of adjuster rod 5.2 Ð 6.2 mm (0.205 Ð 0.244 in)
Belt ten-
sionerSpacer O.D. 17.955 Ð 17.975 mm (0.7069 Ð 0.7077 in)
Tensioner bush I.D. 18.00 Ð 18.08 mm (0.7087 Ð 0.7118 in)
Clearance between spacer and
bushSTD 0.025 Ð 0.125 mm (0.0010 Ð 0.0049 in)
Limit 0.175 mm (0.0069 in)
Side clearance of spacerSTD 0.2 Ð 0.55 mm (0.0079 Ð 0.0217 in)
Limit 0.81 mm (0.0319 in)
CamshaftBend limit 0.020 mm (0.0008 in)
Thrust clearanceSTD 0.040 Ð 0.080 mm (0.0016 Ð 0.0031 in)
Limit 0.10 mm (0.0039 in)
Cam lobe heightIntakeSTD 42.20 Ð 42.30 mm (1.6614 Ð 1.6654 in)
Limit 42.04 mm (1.6551 in)
ExhaustSTDFront: 42.50 Ð 42.60 mm
Rear: 41.40 Ð 41.50 mm(1.6732 Ð 1.6772 in) (1.6299
Ð 1.6339 in)
LimitFront: 42.34 mm Rear: 41.24
mm(1.6669 in) (1.6236 in)
Camshaft journal O.D.Front 31.946 Ð 31.963 mm (1.2577 Ð 1.2584 in)
Center 27.946 Ð 27.963 mm (1.1002 Ð 1.1009 in)
Rear 27.946 Ð 27.963 mm (1.1002 Ð 1.1009 in)
Camshaft journal hole I.D.Front 32.000 Ð 32.018 mm (1.2598 Ð 1.2605 in)
Center 28.000 Ð 28.018 mm (1.1024 Ð 1.1031 in)
Rear 28.000 Ð 28.018 mm (1.1024 Ð 1.1031 in)
Oil clearanceSTD 0.037 Ð 0.072 mm (0.0015 Ð 0.0028 in)
Limit 0.10 mm (0.0039 in)
Cylinder
headSurface warpage limit 0.05 mm (0.0020 in)
Surface grinding limit 0.3 mm (0.012 in)
Standard height 127.5 mm (5.02 in)
Valve seatRefacing angle 90É
Contacting widthIntakeSTD 1.0 mm (0.039 in)
Limit 1.7 mm (0.067 in)
ExhaustSTD 1.5 mm (0.059 in)
Limit 2.2 mm (0.087 in)
Valve guideInner diameter 6.000 Ð 6.015 mm (0.2362 Ð 0.2368 in)
Protrusion above head 12.0 Ð 12.4 mm (0.472 Ð 0.488 in)
ValveHead edge thicknessIntakeSTD 1.2 mm (0.047 in)
Limit 0.8 mm (0.031 in)
ExhaustSTD 1.5 mm (0.059 in)
Limit 0.8 mm (0.031 in)
Stem diameterIntake 5.950 Ð 5.965 mm (0.2343 Ð 0.2348 in)
Exhaust 5.950 Ð 5.965 mm (0.2343 Ð 0.2348 in)
Stem oil clearanceSTDIntake 0.035 Ð 0.062 mm (0.0014 Ð 0.0024 in)
Exhaust 0.040 Ð 0.067 mm (0.0016 Ð 0.0026 in)
Limit Ð 0.15 mm (0.0059 in)
Overall lengthIntake 105.9 mm (4.169 in)
Exhaust 106.2 mm (4.181 in)
3
[S1B0]2-3bSPECIFICATIONS AND SERVICE DATA
1. Engine

Valve
springFree length 48.04 mm (1.8913 in)
Squareness 2.5É, 2.1 mm (0.083 in)
Tension/spring height146.1 Ð 167.7 N (14.9 Ð 17.1 kg, 32.9 Ð 37.7 lb)/42.0 mm
(1.654 in) 455.0 Ð 523.7 N (46.4 Ð 53.4 kg, 102.3 Ð 117.7
lb)/33.4 mm (1.315 in)
Cylinder
blockSurface warpage limit (mating with cylinder head) 0.05 mm (0.0020 in)
Surface grinding limit 0.1 mm (0.004 in)
Cylinder bore STDA 99.505 Ð 99.515 mm (3.9175 Ð 3.9179 in)
B 99.495 Ð 99.505 mm (3.9171 Ð 3.9175 in)
TaperSTD 0.015 mm (0.0006 in)
Limit 0.050 mm (0.0020 in)
Out-of-roundnessSTD 0.010 mm (0.0004 in)
Limit 0.050 mm (0.0020 in)
Piston clearanceSTD 0.010 Ð 0.030 mm (0.0004 Ð 0.0012 in)
Limit 0.050 mm (0.0020 in)
Enlarging (boring) limit 0.5 mm (0.020 in)
Piston Outer diameterSTDA 99.485 Ð 99.495 mm (3.9167 Ð 3.9171 in)
B 99.475 Ð 99.485 mm (3.9163 Ð 3.9167 in)
0.25 mm (0.0098 in) OS 99.725 Ð 99.735 mm (3.9262 Ð 3.9266 in)
0.50 mm (0.0197 in) OS 99.975 Ð 99.985 mm (3.9360 Ð 3.9364 in)
Piston pinStandard clearance between piston
pin and hole in pistonSTD 0.004 Ð 0.010 mm (0.0002 Ð 0.0004 in)
Limit 0.020 mm (0.0008 in)
Degree of fitPiston pin must be fitted into position with thumb at 20ÉC
(68ÉF).
Piston ringPiston ring gapTop ringSTD 0.20 Ð 0.35 mm (0.0079 Ð 0.0138 in)
Limit 1.0 mm (0.039 in)
Second
ringSTD 0.37 Ð 0.52 mm (0.0146 Ð 0.0205 in)
Limit 1.0 mm (0.039 in)
Oil ringSTD 0.20 Ð 0.60 mm (0.0079 Ð 0.0236 in)
Limit 1.5 mm (0.059 in)
Clearance between
piston ring and piston
ring grooveTop ringSTD 0.040 Ð 0.080 mm (0.0016 Ð 0.0031 in)
Limit 0.15 mm (0.0059 in)
Second
ringSTD 0.030 Ð 0.070 mm (0.0012 Ð 0.0028 in)
Limit 0.15 mm (0.0059 in)
Connecting
rodBend twist per 100 mm (3.94 in) in
lengthLimit 0.10 mm (0.0039 in)
Side clearanceSTD 0.070 Ð 0.330 mm (0.0028 Ð 0.0130 in)
Limit 0.4 mm (0.016 in)
Connecting
rod bearingOil clearanceSTD 0.010 Ð 0.038 mm (0.0004 Ð 0.0015 in)
Limit 0.05 mm (0.0020 in)
Thickness at center portionSTD 1.492 Ð 1.501 mm (0.0587 Ð 0.0591 in)
0.03 mm
(0.0012 in)
US1.510 Ð 1.513 mm (0.0594 Ð 0.0596 in)
0.05 mm
(0.0020 in)
US1.520 Ð 1.523 mm (0.0598 Ð 0.0600 in)
0.25 mm
(0.0098 in)
US1.620 Ð 1.623 mm (0.0638 Ð 0.0639 in)
Connecting
rod bush-
ingClearance between piston pin and
bushingSTD 0 Ð 0.022 mm (0 Ð 0.0009 in)
Limit 0.030 mm (0.0012 in)
4
2-3b[S1B0]SPECIFICATIONS AND SERVICE DATA
1. Engine

5) Check cam face condition; remove minor faults
by grinding with oil stone. Measure the cam height
H; replace if the limit has been exceeded.
Cam height: H
Standard:
Intake:
42.20 Ð 42.30 mm (1.6614 Ð 1.6654 in)
Exhaust:
Front: 42.50 Ð 42.60 mm (1.6732 Ð
1.6772 in)
Rear: 41.40 Ð 41.50 mm (1.6299 Ð 1.6339
in)
Limit:
Intake:
42.04 mm (1.6551 in)
Exhaust:
Front: 42.34 mm (1.6669 in)
Rear: 41.24 mm (1.6236 in)
Cam base circle diameter A:
28.0 mm (1.102 in)
B2M1209A
6) Measure the thrust clearance of camshaft with
dial gauge. If the clearance exceeds the limit,
replace caps and cylinder head as a set. If neces-
sary replace camshaft.
Standard:
0.040 Ð 0.080 mm (0.0016 Ð 0.0031 in)
Limit:
0.1 mm (0.004 in)
B2M1217
32
2-3b[W3B1]SERVICE PROCEDURE
3. Camshaft

2) Compress the valve spring and remove the
valve spring retainer key. Remove each valve and
valve spring.
ST1 498267600 CYLINDER HEAD TABLE
ST2 499718000 VALVE SPRING REMOVER
CAUTION:
IKeep removed parts in order for re-installing
in their original positions.
IMark each valve to prevent confusion.
IUse extreme care not to damage the lips of
the intake valve oil seals and exhaust valve oil
seals.
B2M1221A
C: INSPECTION
1. CYLINDER HEAD
1) Make sure that no crack or other damage
exists. In addition to visual inspection, inspect
important areas by means of red check.2) Measure the warping of the cylinder head sur-
face that mates with crankcase by using a straight
edge and thickness gauge.
If the warping exceeds 0.05 mm (0.0020 in),
regrind the surface with a surface grinder.
Warping limit:
0.05 mm (0.0020 in)
Grinding limit:
0.3 mm (0.012 in)
Standard height of cylinder head:
127.5 mm (5.02 in)
CAUTION:
Uneven torque for the cylinder head nuts can
cause warping. When reassembling, pay spe-
cial attention to the torque so as to tighten
evenly.
G2M0760
38
2-3b[W4C1]SERVICE PROCEDURE
4. Cylinder Head

5. VALVE SPRINGS
1) Check valve springs for damage, free length,
and tension. Replace valve spring if it is not to the
specifications presented in the table.
2) To measure the squareness of the valve spring,
stand the spring on a surface plate and measure
its deflection at the top using a try square.
Valve spring
Free length 39.8 mm (1.567 in)
Tension/spring height228.5 Ð 261.8 N
(23.3 Ð 26.7 kg, 51.4 Ð 58.9
lb)/31.0 mm (1.220 in)
462.9 Ð 531.5 N
(47.2 Ð 54.2 kg, 104.1 Ð 119.5
lb)/23.2 mm (0.913 in)
Squareness 2.5É, 1.7 mm (0.067 in)
G2M0154
6. INTAKE AND EXHAUST VALVE OIL
SEAL
Replace oil seal with new one, if lip is damaged or
spring out of place, or when the surfaces of intake
valve and valve seat are reconditioned or intake
valve guide is replaced.
1) Place cylinder head on ST1.
2) Press in oil seal to the specified dimension indi-
cated in the figure by using ST2.
ST1 498267600 CYLINDER HEAD TABLE
ST2 498857100 VALVE OIL SEAL GUIDE
CAUTION:
IApply engine oil to oil seal before force-fit-
ting.
IDifferentiate between intake valve oil seal
and exhaust valve oil seal by noting their dif-
ference in color.
Color of rubber part:
Intake [Black]
Exhaust [Brown]
Color of spring part:
Intake [Silver]
Exhaust [Silver]
B2M1399A
7. VALVE LIFTER
1) Check valve lifter visually.
2) Measure outer diameter of valve lifter.
Outer diameter:
32.959 Ð 32.975 mm (1.2976 Ð 1.2982 in)
B2M1222
41
[W4C7]2-3bSERVICE PROCEDURE
4. Cylinder Head

3. CRANKSHAFT AND PISTON
B2M1320I
(1) Connecting rod cap
(2) Connecting rod bearing(3) Top ring
(4) Second ring(5) Oil ring
(6) Circlip
1) Remove connecting rod cap.
2) Remove connecting rod bearing.
CAUTION:
Arrange removed connecting rod, connecting
rod cap and bearing in order to prevent confu-
sion.
3) Remove piston rings using the piston ring
expander.
4) Remove the oil ring by hand.
CAUTION:
Arrange the removed piston rings in good
order to prevent confusion.
5) Remove circlip.
C: INSPECTION
1. CYLINDER BLOCK
1) Check for cracks and damage visually.
Especially, inspect important parts by means of red
lead check.
2) Check the oil passages for clogging.
3) Inspect crankcase surface that mates with cyl-
inder head for warping by using a straight edge,
and correct by grinding if necessary.
Warping limit:
0.05 mm (0.0020 in)
Grinding limit:
0.1 mm (0.004 in)
Standard height of cylinder block:
201.0 mm (7.91 in)
55
[W5C1]2-3bSERVICE PROCEDURE
5. Cylinder Block

2. CYLINDER AND PISTON
1) The cylinder bore size is stamped on the cylin-
der block's front upper surface.
NOTE:
Standard sized pistons are classified into two
grades, ªAº and ªBº. These grades should be used
as a guide line in selecting a standard piston.
Standard diameter:
A: 99.505 Ð 99.515 mm (3.9175 Ð 3.9179
in)
B: 99.495 Ð 99.505 mm (3.9171 Ð 3.9175
in)
H2M1732A
2) How to measure the inner diameter of each
cylinder
Measure the inner diameter of each cylinder in
both the thrust and piston pin directions at the
heights shown in figure, using a cylinder bore
gauge.
CAUTION:
Measurement should be performed at a tem-
perature 20ÉC (68ÉF).
Taper:
Standard
0.015 mm (0.0006 in)
Limit
0.050 mm (0.0020 in)
Out-of-roundness:
Standard
0.010 mm (0.0004 in)
Limit
0.050 mm (0.0020 in)
G2M0170
3) When piston is to be replaced due to general or
cylinder wear, determine a suitable sized piston by
measuring the piston clearance.
56
2-3b[W5C2]SERVICE PROCEDURE
5. Cylinder Block

4) How to measure the outer diameter of each
piston
Measure the outer diameter of each piston at the
height shown in figure. (Thrust direction)
CAUTION:
Measurement should be performed at a tem-
perature of 20ÉC (68ÉF).
Piston grade point H:
37.0 mm (1.457 in)
Piston outer diameter:
Standard
A: 99.485 Ð 99.495 mm (3.9167 Ð 3.9171
in)
B: 99.475 Ð 99.485 mm (3.9163 Ð 3.9167
in)
0.25 mm (0.0098 in) oversize
99.725 Ð 99.735 mm (3.9262 Ð 3.9266 in)
0.50 mm (0.0197 in) oversize
99.975 Ð 99.985 mm (3.9360 Ð 3.9364 in)
B2M1305A
5) Calculate the clearance between cylinder and
piston.
CAUTION:
Measurement should be performed at a tem-
perature of 20ÉC (68ÉF).
Cylinder to piston clearance at 20ÉC (68ÉF):
Standard
0.010 Ð 0.030 mm (0.0004 Ð 0.0012 in)
Limit
0.050 mm (0.0020 in)
6) Boring and honing
(1) If the value of taper, out-of-roundness, or
cylinder-to-piston clearance measured exceeds
the specified limit or if there is any damage on
the cylinder wall, rebore it to use an oversize
piston.
CAUTION:
When any of the cylinders needs reboring, all
other cylinders must be bored at the same
time, and use oversize pistons. Do not perform
boring on one cylinder only, nor use an over-
size piston for one cylinder only.(2) If the cylinder inner diameter exceeds the
limit after boring and honing, replace the crank-
case.
CAUTION:
Immediately after reboring, the cylinder diam-
eter may differ from its real diameter due to
temperature rise. Thus, pay attention to this
when measuring the cylinder diameter.
Limit of cylinder enlarging (boring):
0.5 mm (0.020 in)
3. PISTON AND PISTON PIN
1) Check pistons and piston pins for damage,
cracks, and wear and the piston ring grooves for
wear and damage. Replace if defective.
2) Measure the piston-to-cylinder clearance at
each cylinder.
If any of the clearances is not to specification,
replace the piston or bore the cylinder to use an
oversize piston.
3) Make sure that piston pin can be inserted into
the piston pin hole with a thumb at 20ÉC (68ÉF).
Replace if defective.
Standard clearance between piston pin and
hole in piston:
Standard
0.004 Ð 0.010 mm (0.0002 Ð 0.0004 in)
Limit
0.020 mm (0.0008 in)
B2M1401
B2M0084A
57
[W5C3]2-3bSERVICE PROCEDURE
5. Cylinder Block