Inspection Of Pistons - TOHATSU MX 50D2 Service Manual

Power Unit
a
5-62
b

18) 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 (2.6756 in)
Oversized Piston : 68.46 mm (2.6953 in)
Functional Limit a :
Standard Piston : 67.90 mm (2.673 in)
Oversized Piston : 68.40 mm (2.69 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 (0.00315 - 0.00472 in)
Functional Limit :
0.21 mm (0.00827 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
Functional Limit :
Top Ring
Second Ring
GB
0.22 - 0.37 mm
(0.009 - 0.015 in)
0.33 - 0.48 mm
(0.013 - 0.019 in)
}
1.0 mm
(0.00394 in)
2st X50D2 2011