Inspection Of Pistons - TOHATSU MD 70-90C2 Service Manual

2) Calculate taper of inner diameter of the cylinder.
Replace the cylinder or use oversized piston if the taper
is equal to or over the specified value.
Calculation of taper :
(Measurement Point) a
D -D
1 5
(Measurement Point) c
D -D
2 6
Functional Limit of taper :
0.08 mm (0.0032 in)
3) Calculate out-of-roundness of inner diameter of the cylinder.
Replace the cylinder or use oversized piston if the out-of-
roundness is equal to or over the specified value.
Calculation of out-of-roundness :
Maximum of the following value
(D -D )
2 1
(D -D )
4 3
(D -D )
6 5
Functional Limit of out-of-roundness :
0.05 mm (0.0020 in)

24) 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 :
11.5 mm (0.45 in) above bottom end of piston skirt.
approximately 90 degrees from pin hole.
Standard Value a :
Standard Piston : 85.85 mm (3.3799 in)
Oversized Piston : 86.35 mm (3.3996 in)
Functional Limit a :
85.79 mm (3.3776 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 : 0.13 - 0.20 mm (0.0051 - 0.0079 in)
Functional Limit :
0.30 mm (0.0118 in)
Calculation of Piston Clearance :
Cylinder Inner Diameter - Piston Outer
Diameter
Use the maximum value of the cylinder inner
diameter measured.
TLDI 75/90C2 2010
D2
D4
D6
a 10mm (0.39 in) d Crank Shaft Direction
b 30mm (1.18 in) e Crank Web Direction
c 80mm (3.15 in)
a
D1
a
b
D3
c
D5
d
e
b
5-37
5