TOHATSU MD 30B2 Service Manual page 161

29) Inspection of Pistons
1. Inspection of Piston Outer Diameter
Measure piston outer diameter, and replace the piston if
the outer diameter is less than the functional Limit.
Measurement Point b :
12 mm (0.47 in) above bottom end of piston skirt.
approximately 90 degrees from pin hole.
Standard Value a :
Standard Piston : 67.96 mm (2.6755 in)
Oversized Piston : 68.46 mm (2.6953 in)
Functional Limit a :
67.90 mm (2.6732 in)
2. Inspection of Piston Clearance
Calculate piston clearance, and if it is over the limit,
replace piston or any of piston rings, replace cylinder, or
use oversized piston.
Piston Clearance :
Standard Value : 0.08 – 0.12 mm (0.0031 – 0.0047 in)
Functional Limit :
0.21 mm (0.0083 in)
Calculation of Piston Clearance :
Cylinder Inner Diameter – Piston Outer
Diameter
Use the maximum value of the cylinder inner
diameter measured.
3. Inspection of Piston Rings
1) Push a piston ring into the cylinder by using top surface
of a piston.
2) Use thickness gauge to measure piston ring gap.
Replace piston ring if the gap is over specified value.
Thickness Gauge :
Commercially Available Item
Piston Ring End Gap : Standard Value
Top Ring
Second Ring
Third Ring
Functional Limit :
a Top Ring
b Second Ring
c Third Ring
TLD D30/40/50B2 2013
}
0.38 – 0.53 mm
(0.0150 – 0.0209 in)
}
0.80 mm
(0.0315 in)
b
a
5
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