JUKI MF-7700D Series Engineer's Manual page 25

Adjustment Procedure
1. To adjust the timing relation between the needle and the looper,
remove the top cover, loosen four setscrews
turn upper pulley
2. Adjusting procedure
(1) When adjusting the timing to "0" (zero)
1) In case dimension
dimension when the looper retreats, the looper timing is
B
retarded (needle timing is advanced). In this case, loosen
setscrews in the sprocket and finely turn upper pulley
the reverse direction.
2) In case dimension
dimension when the looper retreats, the looper timing is
B
advanced (needle timing is retarded). In this case, loosen
setscrews in the sprocket and finely turn upper pulley
the normal direction.
(Caution) Be careful not to excessively turn upper pulley
3. After the adjustment, fix four setscrews
in the state that the sprocket is held.
when the looper advances is smaller than
A
when the looper advances is larger than
A
in the sprocket.
in the sprocket and
in
in
.
– 21 –
Results of Improper Adjustment
o When the difference in timing
(going and returning) of looper is
excessively large, stitch skipping
or entangling of needle thread
will be caused.