60H5E11
Power unit
POWR
Oversize piston:
1st : 90.145 - 90.165mm
(3.5490 - 3.5498 in)
2nd : 90.395 - 90.415 mm
(3.5589 - 3.5596 in)
Piston ring dimensions
(Top ring, Second ring):
B:1.97 - 1.99mm
(0.0776 - 0.0783 in)
T: 2.7-2.9mm (0.1063 - 0.1142 in)
at 20°C (68 °F)
5-31
5. Measure the cylinder bore with cylinder
gauge. Calculate the cylinder bore diam-
eter (D), taper (T), and roundness (R). If
the results exceeded the specified limit,
rebore the cylinder sleeve, or replace the
cylinder block.
60H50480
A:
10mm (0.039 in) to the cylinder head top
surface
B:
5mm (0.20 in) above the exhaust port up-
per edge
C:
5mm (0.20 in) below the scavenging port
lower edge
NOTE:
• Measure the cylinder bore diameter at 6 po-
sitions shown.
• To obtain the cylinder bore diameter(D), cal-
culate the largest of D1-D6 measurements.
• Taper(T) is obtained by subtracting D5 from
D1, and D6 from D2 and selecting the maxi-
mum value.
• To obtain the out of round(R), calculate the
difference between D1 and D2, D3 and D4,
and D5 and D6 respectively. The largest dif-
ference of the three shall apply.
• Oversize pistons is available in two sizes.
Checking the piston
1. Check the piston outside diameter. Re-
place the piston if the diameter is out of
specification.
60H50490
2. Check the piston clearance. Replace the
piston and the piston ring, or the cylinder
block if out of specification.
3. Check the piston ring dimensions of B and
T. Replace the piston ring if the dimension
is out of specification.
60H50500
Specified limits
Cylinder bore diameter(D) :
90.10mm(3.5472in)
at 20 °C (68 °F)
Taper(T) : 0.08mm(0.0031in)
Out of round(R) : 0.05mm(0.0020in)
at 20 °C (68 °F)
Piston outside diameter:
89.895 - 89.915mm
(3.5392 - 3.5400 in)
at 20°C (68 °F)
A
: 10 mm (0.39 in)
Piston clearance:
0.100 - 0.106mm (0.0039 - 0.0042 in)
at 20°C (68 °F)
T
B