12
Connecting rot neck and main shaft neck matching group number is in the table below:
Connecting rod neck matching group Main shaft neck matching group
Group and
mark
Connecting rod neck
dimension(
Ф
40
0
-0.024
)
Group and
mark
Main shaft neck dimension
(
Ф
43
0
-0.024
)
1
≥
－
0.024
≤
－
0.016
1
≥
－
0.024
≤
－
0.016
2
＞－
0.016
≤
－
0.008
2
＞－
0.016
≤
－
0.008
3
＞－
0.008
≤
0
3
＞－
0.008
≤
0
3.3.2 Main shaft bearing
Main shaft bearing grouping according to the dimension of centre thickness see the table below:
Main shaft bearing matching group
Group and mark
Identifying Color
Centre thickness( 2
+0.006
-0.014
)
1
Yellow
≥
－
0.014
≤
－
0.010
2
Green
＞－
0.010
≤
－
0.006
3
Brown
＞－
0.006
≤
－
0.002
4
Black
＞－
0.002
≤
+0.002
5
Blue
＞
+0.002
≤
+0.006
When fitting in order to ensure the bearing clearance it needed to matching on group ,the matching
relation is in the table blow.
Main bearing matching relation
Main shaft neck matching group number
Main bearing matching group
number
1 2 3
4
3
2
1
5
4
3
2
Main bearing hole matching
group number
6
5
4
3
Note:
(1) Main bearing matching group number=main bearing hole matching group number-main shaft
neck matching group number
(2
）
Upper and lower bearing should be fitted with the same group bearing set.
3.4 PISTON AND CONNECTING ROD ASSEMBLY
Piston is made of special aluminum alloy. There are two gas rings and one oil ring on each piston.
The surfaces of the first gas ring and oil ring are chromium plated The second gas ring is slightly
conical and serves to proof gas and form lubricating oil zone (when piston is going upwards) and
scrape oil (when piston is going downwards). The combined oil ring consists of an upper scrape ring, a
lower scrape ring and a compound ring in the middle.
The oil ring has radial and axial sealing function and can prevent lubricating oil enter combustion
chamber.
Piston pin is pressed into the hole of connecting rod with interference. In order to prevent
knocking .the hole of piston pin deviates 1mm from supporting and compressing direction.
