JUKI MO-6900J Series Quick start guide

R
ENGINEER’S MANUAL
29355807
No.E350-01
Super-High-Speed Overlock Machine
High-Speed Overlock Machine / Safety Stitch Machine
MO-6000S series
MO-6900G series (for Extra-heavy-weight Materials)
High-Speed Variable Top Feed Overlock Machine
MO-6900R series
MO-6900J series (for Extra-heavy-weight Materials)

PREFACE
This Engineer’s Manual is written for the technical personnel who are responsible for the service and maintenance of
the machine.
The Instruction Manual for these machines intended for the maintenance personnel and operators at an apparel
factory contains operating instructions in detail. And this manual describes “Standard Adjustment”, “Adjustment
Procedures”, “Results of Improper Adjustment”, and other important information which are not covered by the Instruction
Manual.
It is advisable to use the relevant Instruction Manual and Parts List described below together with this Engineer's
Manual when carrying out the maintenance of these machines.
In addition, for the motor for the sewing machine with thread trimmer, refer to the separate Instruction Manual or
Engineer’s Manual for the motor. And for the control panel, refer to the Instruction Manual for the control panel.
This manual gives the “Standard Adjustment” on the former page under which the most basic adjustment value is
described, and on the latter page “Results of Improper Adjustment” under which stitching errors and troubles arising
from mechanical failures are described together with the “Adjustment Procedures”.
MO-6900S MO-6700S MO-6900G MO-6900R MO-6900J
Part No. Part No. Part No. Part No. Part No.
29351707 29351707 29351707 29356409 29363009
29351806 29352408 29352309 29356201 29362803
Model
Name of part
Instruction Manual
Parts List

CONTENTS
1. SPECIFICATIONS ............................................................................................. 1
(1) MO-6700S SERIES ........................................................................................................... 1
(2) MO-6900S SERIES ........................................................................................................... 2
(3) MO-6900G SERIES........................................................................................................... 3
(4) MO-6900R SERIES........................................................................................................... 4
(5) MO-6900J SERIES............................................................................................................ 5
2. MODEL NUMBERING SYSTEM ....................................................................... 6
3. STANDARD ADJUSTMENT ............................................................................. 8
(1) Adjusting the needle height............................................................................................ 8
(2) Positioning the throat plate ............................................................................................ 8
(3) Installing position of the needle clamp ....................................................................... 10
(4) Adjusting the length of the lower looper holder
(Applicable only to MO-6 16S / MO-6916R, G, J series)........................................... 10
(5) Adjusting the lower looper ........................................................................................... 12
1) Returning amount of the lower looper .................................................................................................... 12
2) Clearance between the lower looper and the needle ............................................................................. 12
(6) Position of the upper looper guide .............................................................................. 14
(7) Positioning the upper looper holder............................................................................ 16
(8) Positioning the upper looper........................................................................................ 18
1) Height of the upper looper ...................................................................................................................... 18
2) Longitudinal position of the upper looper................................................................................................ 18
(9) Adjusting the double chain looper
(Applicable only to MO-6 16S/MO-6916R, G, J series) .............................................. 20
1) Returning amount of the double chain looper......................................................................................... 20
2) Longitudinal motion (Avoid motion) ........................................................................................................ 20
3) Clearance between the double chain looper and the needle ................................................................. 20
(10) Adjusting the height and clearance of the needle guard......................................... 22
1) For 1-needle or 2-needle overlock machine ........................................................................................... 22
2) For safely stitch machine ........................................................................................................................ 22
(11) Adjusting the height of the feed dog ......................................................................... 24
(12) Adjusting the tillt of the feed dog............................................................................... 24
(13) Adjusting the differential feed ratio ........................................................................... 26
(14) Longitudinal position of the feed dog ....................................................................... 26
(15) Adjusting the presser foot.......................................................................................... 28
1) Adjusting the tilt of the presser foot ........................................................................................................ 28
2) Adjusting the micro-lifting mechanism of the presser foot ...................................................................... 28
(16) Positioning the upper knife arm shaft ....................................................................... 30
(17) Positioning the upper and lower knives, and available overedge widths.............. 30
1) Lower knife ............................................................................................................................................. 30
2) Upper knife ............................................................................................................................................. 30
3) Overdging width...................................................................................................................................... 30
(18) Resharpening of the knife .......................................................................................... 32
(19) Position of the thread cam (Applicable only to MO-6 16 series)........................ 32
1) Adjustment of the thread cam................................................................................................................. 32
2) Adjusting looper thread cam thread guides A and B and the looper thread cam nail............................. 32

(20) Adjusting the throat plate support............................................................................. 34
(21) Adjusting the feed mechanism cover presser.......................................................... 34
(22) Adjusting the looper cover ......................................................................................... 36
(23) Adjusting the cloth chip cover ................................................................................... 36
(24) Adjusting the needle mechanism............................................................................... 38
(25) Position of the upper looper lubrication pin............................................................. 40
1) Orientation of the lubricating pin ............................................................................................................. 40
2) Setting the lubricating pin ....................................................................................................................... 40
(26) Longitudinal momentum of the top feed dog (Top feed amount) ........................... 42
(27) Vertical momentum of the top feed dog.................................................................... 44
(28) Adjusting the height of the top feed dog................................................................... 46
(29) Locus cut of the top feed dog .................................................................................... 48
(30) Adjusting the longitudinal position of the top feed dog .......................................... 48
(31) Adjusting the lateral position of the top feed dog.................................................... 50
(32) Position of the motion of the top feed dog ............................................................... 52
(33) Adjusting the feed bar guides A and B...................................................................... 54
(34) Adjusting the top feed dog pressure......................................................................... 56
(35) Lifting amount of the top feed dog (when operating the pedal).............................. 56
(36) Height of the presser (pedal operation)..................................................................... 58
(37) Lifting amount of the top feed dog (when the presser lifting lever is operated) ... 60
(38) Position of the thread guides and the looper thread take-ups................................ 62
(39) Adjusting soft chain making mechanism.................................................................. 64
1) Replacing the parts with those exclusively designed for making soft chains ......................................... 64
2) Adjustment value .................................................................................................................................... 64
3) Important points in adjustment ............................................................................................................... 65
(40) Position of the thread guides and the looper thread take-ups of MO-6900G (J)... 66
4. ADDITIONAL INFORMATION AND PRECAUTIONS..................................... 68
(1) Thread tension............................................................................................................... 68
1) Strength of tension spring....................................................................................................................... 68
2) Springs used for each model. ................................................................................................................. 68
(2) Upper looper .................................................................................................................. 69
(3) Center-to-center distance of the upper looper holder ............................................... 69
(4) Caution in assembly...................................................................................................... 69
1) Application of sealant ............................................................................................................................. 69
2) Precautions to be taken with respect to the lubricating components...................................................... 71
(5) Kinds of motor pulleys, belts and frame support plate bolts.................................... 72
1) Motor pulleys and belts........................................................................................................................... 72
2) Pat No. of frame support plate bolt......................................................................................................... 73
(6) Inspection and replacement of the cartridge filter ..................................................... 73
5. ADJUSTMENT OF THE NEEDLE HEIGHT AND LOOPER TIMMING........... 74
(1) MO-6000 SERIES ........................................................................................................ 74
6. TROUBLES AND CORRECTIVE MEASURES............................................... 75
7. DIMENSIONS OF TABLE ............................................................................... 87
(1) Semi-sunken type.......................................................................................................... 87
(2) Fully-suken type ............................................................................................................88

−1−
1. SPECIFICATIONS
(1) MO-6700S SERIES
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Item
Model
Description
Stitch type F. S. T.
Sewing speed
Stitch length
Needle gauge
Overedging width
Differential feed ratio
Needle bar stroke
Needle tilt angle
Needle
Presser lifting amount
Presser foot pressure
Stitch adjusting method
Upper knife
Differential feed adjustment
Weight
Lubrication
Lubricating oil
Needle cooler
Needle thread heat remover
Micro presser lifting device
Motor
7,000 rpm
MO-6704S
1-needle Overlock
machine
JIS E13
(USA standard : 504)
–
1.6, 3.2, 4, 4.8 mm
7.0 mm
MO-6714S
2-needle Overlock
machine
JIS E24
(USA standard : 514)
2, 2.4, 3.2 mm
3.2, 4, 4.8 mm
6.5 mm
MO-6716S
2-needle Safety stitch
machine
JIS E13 + D12
(USA standard : 516)
1.5 to 4 mm
2, 3.2, 4, 4.8 mm
3.2, 4, 4.8, 6.4 mm
7.0 mm
Specifications
0.8 to 4mm
Gathering 1 : 2 (Max.1 : 4), Stretching 1 : 0.7 (Max.1 : 0.6)
24.5mm
20˚
ORGAN DC X 27 (Standard) (DC X 1 can be used as well.)
49N (5Kg)
By pushbutton
Flat knife
By lever with micro adjustment mechanism
28 kg
Gear-type automatic lubrication
*JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Optional
Optional
Provided as standard
2P 550W (In case of 7,000 rpm)
2P 400W (in case of less than 7,000 rpm)
* JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Part No. : MML018900CA (900 mRR
RR
R)

−2−
(2) MO-6900S SERIES
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Item
Model
Description
Stitch type F. S. T.
Sewing speed
Stitch length
Needle gauge
Overedging width
Differential feed ratio
Needle bar stroke
Needle tilt angle
Needle
Presser lifting amount
Presser foot pressure
Stitch adjusting method
Upper knife
Differential feed adjustment
Weight
Lubrication
Lubricating oil
Needle cooler
Needle thread heat remover
Micro presser lifting device
Motor
Specifications
MO-6904S
1-needle Overlock
machine
JIS E13
(USA standard : 504)
8,500 rpm
–
1.6, 3.2, 4, 4.8 mm
7.0 mm
MO-6914S
2-needle Overlock
machine
JIS E24
(USA standard : 514)
2, 2.4, 3.2 mm
3.2, 4, 4.8 mm
6.5 mm
MO-6916S
2-needle Safety stitch
machine
JIS E13 + D12
(USA standard : 516)
1.5 to 4 mm
2, 3.2, 4, 4.8 mm
3.2, 4, 4.8, 6.4 mm
7.0 mm
Gathering 1 : 2 (Max.1 : 4), Stretching 1 : 0.7 (Max.1 : 0.6)
24.5mm
20˚
ORGAN DC X 27 (Standard) (DC X 1 can be used as well.)
49N (5Kg)
By pushbutton
Flat knife
By lever with micro adjustment mechanism
28 kg
Gear-type automatic lubrication
*JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Provided as standard (Excluding some of subclass machines)
Provided as standard (Excluding some of subclass machines)
Provided as standard
2P 550W (In case of not less than 7,000 rpm)
2P 400W (In case of less than 7,000 rpm)
8,000 rpm
0.8 to 4mm
* JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Part No. : MML018900CA (900 mRR
RR
R)

−3−
(3) MO-6900G SERIES
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Item
Model
Description
Stitch type F. S. T.
Sewing speed
Stitch length
Needle gauge
Overedging width
Differential feed ratio
Needle bar stroke
Needle tilt angle
Needle
Presser lifting amount
Presser foot pressure
Stitch adjusting method
Upper knife
Differential feed adjustment
Weight
Lubrication
Lubricating oil
Needle cooler
Needle thread heat remover
Micro presser lifting device
Motor
Specifications
MO-6904G
1-needle Overlock
machine
JIS E13
(USA standard : 504)
2.5 to 5 mm
–
4.8, 10 mm
Gathering 1 : 1.75 (Max.1 : 3.8)
Stretching 1 : 0.6
MO-6914G
2-needle Overlock
machine
JIS E24
(USA standard : 514)
2.5 to 4 mm
2.6 mm
6.4 mm
Gathering 1 : 2 (Max.1 : 3.8)
Stretching 1 : 0.7 (Max.1 : 0.6)
MO-6916G
2-needle Safety stitch
machine
JIS E13 + D12
(USA standard : 516)
2.5 to 5 mm
4.8 mm
4.8, 6.4 mm
Gathering 1 : 1.75 (Max.1 : 3.8)
Stretching 1 : 0.6
6,000 rpm
28.8 mm
20˚
ORGAN DO X 5
Max. 8 mm
49N (5Kg)
By pushbutton
Flat knife
By lever with micro adjustment mechanism
28 kg
Gear-type automatic lubrication
*JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Provided as standard (Excluding some of subclass machines)
Provided as standard (Excluding some of subclass machines)
Provided as standard
2P 400W
* JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Part No. : MML018900CA (900 mRR
RR
R)

−4−
(4) MO-6900R SERIES
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Item
Model
Description
Stitch type F. S. T.
Sewing speed
Stitch length
Needle gauge
Overedging width
Differential feed ratio
Needle bar stroke
Needle tilt angle
Needle
Presser lifting amount
Presser foot pressure
Stitch adjusting method
Upper knife
Vertical amount of top feed dog
Longitudinal amount of top feed dog
Top feed adjusting type
Differential feed adjustment
Weight
Lubrication
Lubricating oil
Needle cooler
Needle thread heat remover
Micro presser lifting device
Motor
Specifications
MO-6904R
1-needle Overlock
machine
JIS E13
(USA standard : 504)
–
3.2, 4, 4.8, 5.6 mm
7.0 mm
MO-6914R
2-needle Overlock
machine
JIS E24
(USA standard : 514)
2 mm
3.2, 4 mm
6.5 mm
MO-6916R
2-needle Safety stitch
machine
JIS E13 + D12
(USA standard : 516)
1.5 to 4 mm
3.2, 4.8 mm
3.2, 4, 4.8, 6.4 mm
5.5 mm
Gathering 1 : 2 (Max.1 : 4), Stretching 1 : 0.7 (Max.1 : 0.6)
24.5mm
20˚
ORGAN DC X 27 (Standard) (DC X 1 can be used as well.)
49N (5Kg)
By pushbutton
Flat knife
3.5 to 8.5 mm
1 to 7.5 mm (depending on the specifications of the respective machines)
By lever
By lever with micro adjustment mechanism
29 kg
Gear-type automatic lubrication
*JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Provided as standard (Excluding some of subclass machines)
Provided as standard (Excluding some of subclass machines)
Provided as standard
2P 550W (In case of not less than 7,000 rpm)
2P 400W (In case of less than 7,000 rpm)
0.8 to 4mm
* JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Part No. : MML018900CA (900 mRR
RR
R)
Feed type Vertical amount of top feed dog
7,000 rpm (longitudinal amount of top feed less than 6 mm)
6,000 rpm (longitudinal amount of top feed 6 to 8.5 mm)

−5−
(5) MO-6900J SERIES
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Item
Model
Description
Stitch type F. S. T.
Sewing speed
Stitch length
Needle gauge
Overedging width
Differential feed ratio
Needle bar stroke
Needle tilt angle
Needle
Presser lifting amount
Presser foot pressure
Stitch adjusting method
Upper knife
Vertical amount of top feed dog
Longitudinal amount of top feed dog
Top feed adjusting type
Differential feed adjustment
Weight
Lubrication
Lubricating oil
Needle cooler
Needle thread heat remover
Micro presser lifting device
Motor
Specifications
MO-6904J
1-needle Overlock
machine
JIS E13
(USA standard : 504)
2.5 to 5 mm
–
4.8 mm
Gathering 1 : 1.75 (Max.1 : 3.8)
Stretching 1 : 0.6
MO-6914J
2-needle Overlock
machine
JIS E24
(USA standard : 514)
2.6 mm
6.4 mm
Gathering 1 : 2 (Max.1 : 3.8)
Stretching 1 : 0.7 (Max.1 : 0.6)
MO-6916J
2-needle Safety stitch
machine
JIS E13 + D12
(USA standard : 516)
2.5 to 5 mm
4.8 mm
4.8, 6.4 mm
Gathering 1 : 1.75 (Max.1 : 3.8)
Stretching 1 : 0.6
28.8mm
20˚
ORGAN DO X 5
Max. 8 mm
49N (5Kg)
By pushbutton
Square knife
3.5 to 8.5 mm
2.7 to 7.0 mm (depending on the specifications of the respective machines)
By lever
By lever with micro adjustment mechanism
29 kg
Gear-type automatic lubrication
*JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Provided as standard (Excluding some of subclass machines)
Provided as standard (Excluding some of subclass machines)
Provided as standard
2P 400W
* JUKI MACHINE OIL 18 (Equivalent to ISO VG 18)
Part No. : MML018900CA (900 mRR
RR
R)
Feed type Vertical amount of top feed dog
6,000 rpm
2.5 to 4 mm

−6−
2. MODEL NUMBERING SYSTEM
MO-6000 SERIES MODEL NUMBERING SYSTEM
MO6 / –
1 2 3 4 5 6 7 8 9 10 11 12 1314 15 16 17 18 19 20 21 22
4 Machine code
7 6700 series
9 6900 series
5. 6 Seam code
03 Splicing
04 1-needle 3-thread overlock (504)
05 For blind hemmong (505)
12 2-needle 4-thread mock safety stitch (512)
14 2-needle 4-thread overlock (514)
16 2-needle 5-thread safety stitch (516)
43 3-needle 6-thread safety stitch
45 2-needle double chainstitch
8 Needle gauge code
0 1-needle
B 2.0 mm
C 2.4 mm,
2.6 mm (for extra-
heavy-weight
materials)
D 3.2 mm
E 4.0 mm
F 4.8 mm
1 4.8 mm + 2.0 mm
7 Basic specification code
S Standard
G Extra heavy-weight materials
R Variable top feed type
J Variable top feed type for
extra heavy-weight materials
9 Overedging width code
A 1.6 mm
D 3.2 mm
E 4.0 mm
F 4.8 mm
H 6.4 mm
M 10.0 mm
N 18.0 mm
10 Feeddogcode
4 2-row
5 1-row
6 3-row
7 4-row
12 Application code
Classification based on type of operation
and process
0 Standard
1 For blind stitching
2 For gathering
4 For attaching tape
5 For binding
6 For binding tape
D Splicing *
E Car mattress
F Soft chain
* In case of the splicing, 13th figure is [1].
11 Material code
Classification based on materials to be used
For light-weight materials such as
shirts or the like
Knit wear only
General fabrics
Knit wear only such as sweater or
the like
Medium-weight to heavy-weight
materials such as denim or the like
For heavy-weight materials
Heavy-weightmaterialsforjeans,car
mattress, etc.
1
2
3
4
5
6
7
Extra light-weight to light-
weight materials
Light-weight to medium-
weight materials
Medium-weight to heavy-
weight materials
Heavy-weight to extra
heavy-weight materials
* 6900 only
*
*
*

−7−
13 Special machine code
Special classification of machine, structure and
specification other than gauge set
0 Standard
6 Feed dog provided with a lip
7 Upper looper high throw type
F For swim suits
H Upper looper extra high throw type
M For zipper
1 For splicing
15 to 18 Device and attachment code
G02/Q141 Presser foot/tape guide for attaching tape
G39/Q141 Presser foot (for sharp curve)/tape guide for
attaching tape
L121 Blind hemming ruler
S159 Swingtyperuffler (pedal-interlockingtypeforsafety
stitch)
S161 Swing type ruffler (Manual lever type for safety
stitch)
S162 Swing type ruffler (Manual lever type for overlock)
N077 Four-fold binder
* The general export specification is for Hong Kong, U.S.A., Japan and Singapore.
20 Machine head code
A Standard machine head
(Common to all specifications)
21 Accessory code
A For general export *
B For JE
G For China
22 Machine head code
0 Fully-sunken type
1 Semi-sunken type
The numberings after “–” (hyphen) of 19th figure will be used on
and after April 1, 2002. They are not described on the catalogue or the like.

−8−
Standard Adjustment
3. STANDARD ADJUSTMENT
(1) Adjusting the needle height
When the needle(s) is in the highest position,
the needle height from the throat plate surface should be as shown below.
(2) Positioning the throat plate
The needle entry point should be such that the distances listed below are provided between the
needle slot edge of the throat plate and the center of needle.
Note that “A=1.8” and “B=1.5”
for MO-6 16S (R) - -60H,
“A=1.6” and “B=1.3” for MO-69 G, J
(Unit : mm)
Overlock side A 1.3
Double-chainstitch side B 1.0
10˚
A
B
604
614
616
e
1-needle/
2-needle : left
10.5
11.3
11.3
11.0
11.3
10.5
11.3
10.5
11.3
13
10.5
11.3
9.8
15.4
14.4
15.4
14.1
14.1
2-needle : right
–
–
–
9.4
9.9
9.1
9.9
–
–
–
9.9
9.9
–
–
–
–
12.6
–
The adjustment of needle height for the 2-needle
overlock machine should be made in reference to the
left needle.
Model
MO- 6 04S(R) - - 0
- 6
50M
MO- 6 04S - - H
MO- 6 05S - - H
507
50F
MO- 6 12S -CE4 -40H
MO- 6 14S (R) -B -3 7
20H
40H
MO- 6 16S(R)- - 0
MO- 6 16S(R)- - H
MO- 6 16S(R)- -60H
MO- 6943R - - 7
MO- 6 43S - - H
MO- 6 45S - -360
MO- 6903G -0N6 -3D1
MO- 6904G(J)-0F6 -700
MO- 6905G -0M6 -7 0
MO- 6914G(J)-CH6 -700
MO- 6916G(J)-F 6 -700
(Unit : mm)
1-needle
overlock machine
2-needle overlock
machine Safety stitch
machine MO-6900G, J
MO- 6 12S - -
MO- 6 14S (R) -B -

−9−
Adjustment Procedures Results of Improper Adjustment
1) Take off the upper cover, loosen setscrew 2of needle driving
forked crank 1and move needle driving forked crank 1up or
down to adjust the needle height.
(Caution) Do not fully loosen the setscrew 2of the needle
driving forked crank 1.
If the needle driving forked crank has got out of position
laterally when its setscrew was loosened, fully loosen the
setscrew and turn pulley to allow the forked crank to turn
until it settles by itself. Then tighten the setscrew to fix the
forked crank at that position.
1) Loosen setscrews 2of throat plate base 1and move throat
plate base 1back and forth to adjust dimension A or B.
™Any other needle height than
specified here will badly affect
the action of the lower looper,
the timing for catching the upper
looper thread, etc.
™Improper lateral position of the
needle driving forked crank will
cause seizure, play, or other
troubles.
™Improperly positioned throat
plate will cause needle
breakage, contact of the
needles will the throat plate, or
other troubles.
Needle driving shaft
1
2
12

−10−
(3) Installing position of the needle clamp
Needle clamp connecting stud 1should fit with the bottom end of needle bar 2or spaced within 0 to
0.5 mm.
Standard Adjustment
(4) Adjusting the length of the lower looper holder
(Applicable only to MO-6 16S / MO-6916R, G, J series)
The center-to-center distance should be 26 mm.
At this time, the clearance between the end surface of the arm and the neck of the ball should be
3.5 mm.
3.5 mm
0 to 0.5 mm
Butt the needle clamp with the
bottom end of the needle bar.
26 mm
1
2
3
4
1

−11 −
1) Loosen setscrew 3and adjust, by slightly turning needle clamp
4, the clearance provided between the right-hand side needle
and the lower looper (for 2-needle overlock machine) and the
clearance provided between the needle hole in the throat plate
and the needle (for safety stitch machine).
™If the clearance provided
between the needle and the
looper is excessive, the needle
thread will be likely to skip at the
time of tucking.
™If the clearance provided
between the needle and the
looper is insufficient, the needle
will break or the looper blade
point will be damaged causing
thread breakage.
Adjustment Procedures Results of Improper Adjustment
1) Loosen setscrew 1of the lower looper holder from the rear of
the frame.
Since it is difficult to accurately measure the center-to-center
distance, perform adjustment to provide a 3.5 mm distance
between the end surface of the arm and the neck of the ball as
illustrated.
™Increasing the center-to-center
distance will give a smaller
stroke of the duble chain looper
or lower looper, and decreasing
the distance will give larger
stroke.

−12−
(5) Adjusting the lower looper
1) Returning amount of the lower looper
The distance between the blade point of the
lower looper and the center of the needle
should be as follows when the lower looper is
at the extreme left of its stroke.
2) Clearance between the lower looper and the needle
The clearance should be 0 to 0.1 mm.
Standard Adjustment
Dimension J
4.0
3.7
3.8
3.8
3.8
4.0
2.2
3.7
3.8
2.8
3.8
3.8
1.4
3.5
1.3
3.3
3.5
Model
Safety stitch
machine
K
(66.9±0.2 mm)
0 to 0.1 mm
1-needle overlock
machine
2-needle overlock
machine
MO-
6900G,J
5
(Only MO-69 △△S,R,
G, J series)
(Unit : mm)
J
1
2
3
4
604S(R)
605S
MO- 6 04S(R)- -
MO- 6 04S - -
MO- 6 14S(R) - -3 7
MO- 6 16S(R) - -
0A5 15
MO- -0A4 to 0E4 -210
0D6 3
0F4 3 0
0F6 500
0H4 50M
0D4 to 0E4 4 H
0F6 50H
BD4 to BE4
BD6 to BE6
BD6 to BF6 20H
BE7 4 H
MO- 6 12S -CE4 -40H
50F
507
30
500
BE4
MO- 6 16S(R) -DD -
F
MO- 6 16S(R) -F 6 -60H
MO- 6943R - - 7
MO- 6 43S - - H
MO- 6903G -0N6 -3D1
MO- 6904G(J) -0F6 -700
MO- 6905G -0M6 -7 0
MO- 6914G(J) -CH6 -700
MO- 6916G(J) -F 6 -700
MO- 6 12S -DF6 -
MO- 6 14S(R) -
4 H
5H

−13 −
Adjustment Procedures Results of Improper Adjustment
™Excessive return of the lower
looper tends to cause stitch
skipping when filament thread is
used.
™Insufficient return of the lower
looper tends to cause needle
thread stitch skipping when
spun thread is used.
™Excessive clearance will often
cause needle thread stitch
skipping.
™Insufficient clearance will cause
needle breakage due to the
contact of the looper with the
needle, or produce scratches on
the blade point of the looper,
leading to needle thread
breakage or other troubles.
1) Returning amount of the lower looper
1Loosen setscrew 2of lower looper support arm 1and adjust
lower looper 4to make adjustment of the returning amount.
(Referential information)
1. Radius Kof lower looper 4will be 66.9 mm when the lower
looper is inserted into lower looper support arm 1until it
contacts with stopper pin 3and then is fixed.
2. The rocking angle of the lower looper will be 26˚.
(MO-6 S, R)
The rocking angle of the lower looper will be 32˚.
(MO-69 G, J)
2) Clearance between the lower looper and the needle
MO-6700S Series
1Loosen setscrew 2of lower looper support arm 1to the extent
that it is temporarily tightened. Now, make the adjustment by
moving lower looper support arm 1back and forth.
MO-6900S, R, G, J Series.
1Loosen setscrew 2of lower looper support arm 1to the extent
that it is temporarily tightened. Then finely adjust the longitudinal
position of the looper using fine adjustment screw 5.
2Turn fine adjustment screw 5clockwise to move lower looper
4away from the needle.
Turn the screw counterclockwise to move lower looper 4closer
to it.

−14−
Standard Adjustment
Model
6 04S(R)
605S
MO- 6 04S(R)- -
(6) Position of the upper looper guide
Vertical position :
To be in close contact with the frame guide surface.
Laternal position :
To be pressed against the upper looper guide support
gauge 1.
Safety stitch machine
1-needle overlock machine
2-needle overlock machine
65.8
Upper
looper
guide
support
gauge
13131909 13132006
Model
MO-6900G, J
7
6.3
5.8
6
5.8
4.7
5.5
6.3
5.8
5.8
5.8
4
4.2
4
4.2
4.2
11545100 12375606
7 5.5 6.3 4.7
4.2 4
Maker dot
(Unit : mm)
(Unit : mm)
(Unit : mm)
3 0
500
BE4
MO- 6 16S(R) -DD -
F
MO- 6 16S(R) -F 6 -60H
MO- 6943R - - 7
MO- 6 43S - - H
MO- 6903G -0N6 -3D1
MO- 6904G(J) -0F6 -700
MO- 6905G -0M6 -7 0
MO- 6914G(J) -CH6 -700
MO- 6916G(J) -F 6 -700
1
2
3
4
G
Frame guide surface
Dimension GDimension G
0A5 15
MO- -0A4 to 0E4 -210
0D6 3
0F4 3 0
0F6 500
0H4 50M
0D4 to 0E4 4 H
0F6 50H
BD4 to BE4
BD6 to BE6
BD6 to BF6 20H
BE7 4 H
MO- 6 12S -CE4 -40H
507
50F
MO- 6 04S - -
MO- 6 14S(R)- -3 7
MO- 6 14S(R)- -
MO- 6 12S -DF6 -
MO- 6 16S(R) - -
4 H
50H
6

−15 −
Adjustment Procedures Results of Improper Adjustment
1) Fit upper looper guide support gauge 1over gauge fixing pin
3which has been driven in frame 2and secure the gauge
with an O ring.
Then position the gauge taking the marker dot engraved on it
or the chamfering direction as reference.
2) When installin upper looper guide support 4, press it against
the gauge while keeping the upper looper guide support into
close contact with the frame guide surface, then tighten the
screws.
(Caution) Refer to “4- (4) -1) - 7Various sealants” for the
various sealants.
™If the upper looper guide has
improperly positioned vertically,
it will cause oil leakage or
disturbed path of the upper
looper with resultant stitch
skipping.
™If the upper looper guide has
been inaccurately positioned
laterally, it will cause stitch
skipping, or contact with the
looper.

−16−
Standard Adjustment
(7) Positioning the upper looper holder
The distance between the bottom surface of the frame and the upper end of the upper looper holder
pin 2should be as shown below when the upper looper holder 1is at the highest point of its stroke.
F
Bottom surface of frame
53 mm
1
2
3
4
5
6
1
4
0.2mm
0.2mm
Model
604S(R)
605S
MO- 6 04S(R)- -
Safety stitch machine 1-needle overlock machine
2-needle overlock machine
MO-6900G,J serise
Dimension F
45.0
46.2
48.2
47.3
48.4
46.8
46.9
46.2
48.2
48.4
47.3
48.4
51.2
50.7
51.7
49.3
48.8
(Unit : mm)
MO- 6 14S(R)- -3 7
MO- 6 14S(R)- -
MO- 6 12S -DF6 -
0A5 15
MO- -0A4 to 0E4 -210
0D6 3
0F4 3 0
0F6 500
0H4 50M
0D4 to 0E4 4 H
0F6
50H
BD4 to BE4
BD6 to BE6
BD to BF 20H
BE7 4 H
MO- 6 12S -CE4 -40H
507
50F
MO- 6 16S(R) - -3 0
500
BE4
MO- 6 16S(R)- DD -
F
MO- 6 16S(R) -F 6 -60H
MO- 6943R - - 7
MO- 6 43S - - H
MO- 6903G -0N6 -3D1
MO- 6904G(J)-0F6 -700
MO- 6905G -0M6 -7 0
MO- 6914G(J)-CH6 -700
MO- 6916G(J)-F 6 -700
4 H
5 H
MO- 6 04S - -