Yanmar 3TNV Series, Service Manual

Page: 116 / 213

4. Disassembly, Inspection and Reassembly of Engines
101
(4) Piston
Especially clean the combustion surface,
circumference, ring grooves and piston pin bosses,
and check after removing any carbon deposit. Any
burr at a ring groove or snap ring groove shall be
removed. If crack is suspected, inspect by color
check.
(a) Piston outside diameter measurement
Measure the long diameter at H mm from the bottom
end of the piston of the oval hole in the vertical
direction to the piston pin hole.
Piston outside diameter mm
Model
Outside diameter
Standard
Limit
Clearance between
piston and cylinder
Measurement
position (H)
3TNV82A 81.950 81.980 81.905 0.035 0.065
3,4TNV84(T) 83.945 83.975 83.900
3,4TNV88 87.945 87.975 87.900
0.040 0.070
22 25
4TNV94L 93.945 93.955 93.900 22
4TNV98(T) 97.940 97.950 97.895 22
4TNV106(T) 105.930 105.960 105.880
0.050 0.080
30
If the clearance between piston and cylinder exceeds
the limit, use an oversized piston. (Refer to the tables
of oversized pistons, oversized piston rings and
cylinder boring dimension on 4.4.5(1)(c) in chapter 4.)
(b) Piston pin hole measurement
Measure the outside diameter of piston pin and the
inside diameter of piston pin hole. Calculate the
clearance between piston pin and piston pin hole. If
any data exceeds the limit, replace the part with a new
one.
mm
Model Item Standard Limit
Pin I.D. 23.000 23.009 23.039
Pin O.D. 22.995 23.000 22.965 3TNV82A
Clearance 0.000 0.014 0.074
Pin I.D.
26.000 26.009 26.039
Pin O.D. 25.995 26.000 25.965 TNV84 88
Clearance 0.000 0.014 0.074
Pin I.D.
30.000 30.009 30.039
Pin O.D. 29.989 30.000 29.959
4TNV94L
4TNV98(T)
Clearance 0.000 0.020 0.080
Pin I.D.
37.000 37.011 37.039
Pin O.D. 36.989 37.000 36.959
4TNV106(T)
Clearance 0.000 0.022 0.080