JUKI MF-7900 Series Engineer's Manual page 61

Adjustment procedures
Loosen setscrews ❶ in the looper thread cam ❷ and adjust
1.
while checking that looper thread comes off from the periphery
of the looper thread cam ❷ .
(Caution) When setscrews ❶ in the looper thread cam ❷ are
loosened, looper thread cam ❷ moves in the shaft
direction as well. Assemble so that the clearances
provided between the cam and the thread guide are
equal.
2. Adjusting the looper thread cam thread guide
When the thread drawing amount is desired to be decreased in
case of 2-needle machine or the like, loosen screws ❼ , move
upward thread guides ❺ and ❻ and tighten screws ❼ to fix
them.
A = Decrease
B = Increase
3. Preventing thread winding around the looper thread cam
(1) Loosen nut ❾ .
(2) Slightly loosen screw  so that the thread guide plate ❽ is
able to return to its original state by the spring force.
(3) Tighten nut ❾ . (Tightening torque : 4 ± 0.5 N·m)
(Caution) After tightening nut ❾ , make sure that the thread
guide plate ❽ moves lightly. If the thread guide plate
❽ does not move lightly, perform the adjustment
from step (1) again.
Results of Improper adjustment
◦ When the position of looper
thread cam ❷ slips greatly out of
position, stitch skipping or defect
of thread tightness on the back
of the looper ❹ is apt to occur.
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