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Crank mechanism

Pistons

A piston of an aluminum alloy with a flat bottom.

At the bottom of the piston diameter of the piston specified label and arrow for orientation when installing the piston into the cylinder, which should be directed towards camshaft drive. By weight of the pistons of the engine must not differ by more than 4,9 g

Characteristic	Value
The clearance between the piston and the cylinder, mm
nominal
M 102	0,016-0,040
other models	0,025-0,035
the legal limit in operation	0.10

Bore *

Option mm	Engine model
	M 115,938	M 102,920, 102,939 M	M 102,980, M 102.982	M 115,954
nominal
Class 1	86.98	88,968-88,982	95,468-95,482	93.73
Class 2	-	88,978-88,992	95,478-95,492	-
Class 3	-	88,988-89,002	95,488-95,502
1st oversize
Class 1	87.48	89,468-89,482	95,968-95,982	94.13
Class 2	-	89,478-89,492	95,978-95,992	-
Class 3	-	89,488-89,502	96,988-96,002	-
2nd oversize
Class 1	87.98	89,968-89,982	96,468-96,482	94.53
Class 2	-	89,978-89,992	96,478-96,492	-
Class 3	-	89,988-90,002	96,488-96,502	-
3rd oversize
Class 1	88.48	-	-	-
Option mm	M 123,920, 123,921 M	M 110,923	M 110,984, 110,988 M
nominal
Class 1	85.98	85.98
Class 2	-	-
Class 3	-	-
1st oversize
Class 1	86.48	86.48
Class 2	-	-
Class 3	-	-
2nd oversize
Class 1	86.98	86.98
Class 2	-	-
Class 3	-	-
3rd oversize
Class 1	-	-

* The difference values caused by model year release.

Piston fingers

The piston pin steel, brushed, floating. By axial displacement of the finger is held by retaining rings.

Features piston pin

Option mm	Engine model
	M 102,920, 102,939 M	M 102,980, M 102.982
Diameter
outer	23,995-24,000
interior	15.5
Length	-
The gap between the finger and the sleeve upper crosshead	0,007-0,02
The gap between the pin and piston boss	0,002-0,012

Piston rings

On the outer surface of the piston machined three groove for mounting rings. The situation in the assembly: the mark "TOP" should be upwards. On engines M 102 can be installed piston ring company "Go?�tze" or TRW.

Design features of piston rings firm "Go?�tze"

The top compression ring is cylindrical, with a chamfer on an inner surface, a porous outer surface of the chrome plating. The lower compression ring, conical, with collar. Scraper ring with two-flats, expander coil spring and chrome outer surface.

Design features of piston rings the TRW

The top compression ring is cylindrical, with a chamfer on an inner surface with a chrome polished outer surface of the barrel. Lower compression ring cone with collar and chrome outer surface of the barrel. Scraper ring with two-flats with expander coil spring and chrome outer surface.

Characteristics of piston rings

Option mm	Engine model
	M 115,938	M 102,920, 102,939 M	M 102,980, M 102.982	M 115,954
Clearance height
top compression ring	0.05-0.08	0,05-0,085	0,050-0,085
lower compression ring	0.03-0.06	0.01-0.03	0.03-0.06
oil ring	0.01-0.04	0,01-0,045	0.01-0.04
Marginal gap adjustment operation
top compression ring	0.15
lower compression ring	0.10
oil ring	0.16	0.10		0.16
The gap in the castle
top compression ring	0,30-0,55
lower compression ring	0.25-0.45
oil ring	0.25-0.50
The maximum end gap in service
top compression ring	10	10		10
lower compression ring	0.8	0.8		0.8
oil ring	0.8	0.8		0.8
Option mm	M 123,920, 123,921 M	M 110,923	M 110,984, 110,988 M
Clearance height
top compression ring	0,050-0,085
lower compression ring	0.03-0.06
oil ring	0.01-0.04
Marginal gap adjustment operation
top compression ring	0.15
lower compression ring	0.10
oil ring	0.16
The gap in the castle
top compression ring	0,30-0,55
lower compression ring	0.25-0.45
oil ring	0.25-0.50
The maximum end gap in service
top compression ring	10
lower compression ring	0.8
oil ring	0.8

Cranks

Rod I-section steel, forged with replaceable inserts. Cover the bottom head of a rod section directly. For the supply of oil to metal parts of the connecting rod in the rod hole is drilled. By weight of the connecting rods of the engine must not vary by more than 5 grams

Characteristic	Value
Non-parallelism and flatness holes heads when measured at a distance of 100 mm from the axis of the rod connecting rod, not more, mm
M 102	0,045
M 115	0,030
M 110	0,040
M 123	0,040
The surface roughness of the connection with the piston rod, mm	0,002
Run-out holes of the bottom head of a rod, not more, mm	0.02

Features rods

Option mm	Engine model
	M 115,938	M 102,920, 102,939 M	M 102,980, M 102.982	M 115,954
The diameter of the bottom head of a rod	55,60-55,62	51,60-51,619		55,60-55,62
The diameter of the upper crosshead	29,00-29,02	27,00-27,021		29,00-29,02
Inner diameter of the upper head	26,012-26,018	24,007-24,015		26,012-26,018
The distance between holes heads	148,95-149,05	144,95-145,05		148,95-149,05
The width of the bottom head	32.08-32,10	27,857-27,90		32.08-32.10
Option mm	M 123,920, 123,921 M	M 110,923	M 110,984, 110,988 M
The diameter of the bottom head of a rod	51,60-51,62
The diameter of the upper crosshead	26,00-26,02
Inner diameter of the upper head	23,007-23,013
The distance between holes heads	130,95-131,05
The width of the bottom head	27,86-27,89

The bolts connecting rod cap

Bolts with pulling rod.

Characteristic	Value
Thread diameter	M9h1
The diameter of the rod, mm
M 102
New bolts	8.3-8.4
maximum allowable	8.0
M 115
New bolts	8.3-8.4
maximum allowable	8.0
M 110
New bolts	7.3-7.4
maximum allowable	7.1
M 123
New bolts	7.3-7.4
maximum allowable	7.1
The height of the bolt head (102 M), mm	5.0-5.2
The length of the threaded portion (102 M), mm	40.0
The length to head (M 102), mm	51,7-52,0

Crankshaft

Steel crankshaft, forged four (motor M 123), five (motors M 102 and M 115) or semioporny (engine M 110).

The crankshaft 4-cylinder engine (M 102, M 115) has eight counterweights, 6-cylinder (M 110, M 123) - 12 balances.

Characteristic	Value
Permissible runout cheeks main bearing, mm	0.02
Radii galiteley indigenous and crank pins, mm	2.5-3.0
The diameter of the front end of the crankshaft, mm	29,987-30,000
Permissible runout of the front end of the crankshaft, mm	0,030
The diameter of the bearing surface of the rear oil seal, mm	92,874-92,928
Netsilindrichnost flange to mm	0.02
The beating of the flange up, mm	0.012
The beating of indigenous necks (the crankshaft mounted on the prism necks 1 and 5), up to, mm
2 and cervix 4	0.07
cervical 3	0.10

The clearances of the crankshaft of the engine M 102

Characteristic	Value
Diametrical clearance between the main journal and inserts, mm
nominal	0,025-0,045
limiting the wear in operation	0,070
Diametrical clearance between the crankpin and inserts, mm
nominal	0,030-0,050
limiting the wear in operation	0,070
The axial clearance of the crankshaft, mm
nominal	0,06-0,22
limiting the wear in operation	0.30
The axial clearance between the connecting rod and the crankshaft, mm
nominal	0,11-0,23
limiting the wear in operation	0.50
Permitted roundness of indigenous and crankpins in operation, mm	0,025
Acceptable conicity in operation, mm
crankpins	0,010
main journals	0,015
Voltage unbalance between the crankshaft in operation g.sm	15

Options crankshafts

Option mm	Engine model
	M 115,938	M 102,920, 102,939 M	M 102,980, M 102.982	M 115,954
The diameter of the main journals
nominal
1 class	69,95-69,96	57,935-57,940		69,95-69,96
Class 2	*	57,940-57,945		*
Grade 3	*	57,945-57,950		*
4th grade	*	57,950-57,955		*
Grade 5	*	57,955-57,960		*
6th grade	*	57,960-57,965		*
1st oversize	69,70-69,71	57,705-57,715		69,70-69,71
2nd oversize	69,45-69,46	57,455-57,465		69,45-69,46
3rd oversize	69,20-69,21	57,205-57,215		69,20-69,21
4th oversize	68,95-68,96	57,955-57,965		68,95-68,96
The width of the main journals
Rated	34,00-34,03	28,500-28,521 or 28,600-28,621		34,00-34,03
1st oversize	34,00-34,03	28,700-28,721		34,00-34,03
2nd oversize	to 34.60	28,900-28,921		to 34.60
3rd oversize	to 34.60	29,000-29,021		to 34.60
4th oversize	to 34.60	*		to 34.60
The distance between the bearing surfaces of persistent half rings
	-	23,979-24,000		-
Diameter crankpins
Rated	51,97-51,96	47,955-47,965		51,97-51,96
1st oversize	51,70-51,71	47,705-47,715		51,70-51,71
2nd oversize	51,45-51,46	47,455-47,465		51,45-51,46
3rd oversize	51,20-51,21	47,205-47,215		51,20-51,21
4th oversize	50,95-50,96	46,955-46,965		50,95-50,96
The width of the crank pins
Rated	32,0-32,1	27,000-28,034		32,0-32,1
oversize	to 32.30	to 28.30		to 32.30
Option mm	M 123,920, 123,921 M	M 110,923	M 110,984, 110,988 M
The diameter of the main journals
nominal
1 class	59,95-59,96
Class 2	*
Grade 3	*
4th grade	*
Grade 5	*
6th grade	*
1st oversize	59,70-59,71
2nd oversize	59,45-59,46
3rd oversize	59,20-59,21
4th oversize	58,95-58,96
The width of the main journals
Rated	29,00-29,02
1st oversize	29,00-29,02
2nd oversize	to 29.60
3rd oversize	to 29.60
4th oversize	to 29.60
The distance between the bearing surfaces of persistent half rings
	-	-	-
Diameter crankpins
Rated	47,95-47,96
1st oversize	47,70-47,71
2nd oversize	47,45-47,46
3rd oversize	47,20-47,21
4th oversize	46,95-46,96
The width of the crank pins
Rated	28,00-28,08
oversize	to 28.30

Inserts indigenous and connecting rod bearings

Color marking of bearings: blue or gray.

Characteristic	Value
The width of the pads, mm
Engine M 102 and M 115
Rated	33,80-33,90
repair	34,40-34,60
Engine M 110 and M 123
Rated	28,78-28,90
repair	29,40-29,60

Inserts for all levels of repair are available with excess width and should be finalized by the size of the bearing reground.

Engine Model M 102 issues from July 1986 have a thickness of loose leaves of radical bearings, increased by 0.003 mm in order to reduce the gap and reduce the operating noise of the engine.

Characteristics of loose leaves of radical bearings and rod

Option mm	Engine model
	M 115,938	M 102,920, 102,939 M	M 102,980, M 102.982	M 115,954
The thickness of the main bearing shells
Rated	2.25	2.25		2.25
1st oversize	2.37	2.37		2.37
2nd oversize	2.50	2.50		2.50
3rd oversize	2.62	2.62		2.62
4th oversize	2.75	2.75		2.75
The thickness of the connecting rod bearing liner
Rated	1.80			1.80
1st oversize	1.92			1.92
2nd oversize	2.05			2.05
3rd oversize	2.17	2.18		2.17
4th oversize	2.30			2.30
Option mm	M 123,920, 123,921 M	M 110,923	M 110,984, 110,988 M
The thickness of the main bearing shells
Rated	3.50
1st oversize	3.63
2nd oversize	3.75
3rd oversize	3.88
4th oversize	4.00
The thickness of the connecting rod bearing liner
Rated	1.81
1st oversize	1.93
2nd oversize	2.06
3rd oversize	2.18
4th oversize	2.31

Flywheel engine M 102

The flywheel is secured by eight bolts. Installation hole is opposite the hole in the crankshaft.

Characteristic	Value
The diameter of the spigot ring mm	275,31-275,39
The distance between the working surface of the driven disk and the clutch housing support surface, mm	22,5-22,6
The distance between the working surface of the clutch disc and the flywheel mounting bolt head, mm
nominal	16.6
after grinding, at least	15.5
Flatness of the working surface clutch plate, no more, mm	0.05
The outer diameter of the working surface of the clutch plate, mm	222.0
The outer diameter of the clutch housing support surface, mm	253.0
The diameter of the rod compensating flywheel bolts, mm
new bolts	8.5
minimum	8.0
The length of the bolt to the head, mm
new bolts	22 ?� 0.2
maximum	22.5