JUKI MF-7900 Series Engineer's Manual page 69

Adjustment procedures
1. Changing the needle bar stroke
(1) Loosen setscrew ❻ (remove the rubber plug) in eccentric pin
❺ .
(2) Draw out eccentric pin ❺ by more than 1 mm, turn eccentric
pin ❺ by 180°, position notch mark F of the eccentric pin away
from the center of main shaft, push the pin, and fix the pin with
setscrew ❻ .
(Caution) When it is hard to pull out eccentric pin ❺ , enter an
M4 screw in the M4 screw hole G and pull it out.
* Position of the notch mark of eccentric pin
At the time of needle bar stroke 31 mm :
notch mark is on the side of the center of main shaft.
At the time of needle bar stroke 33 mm :
notch mark is on the side away from the center of main shaft.
(Caution) There is a groove to fit, when eccentric pin ❺ is
turned by 180°, at the fitting section of eccentric pin
❺ and counter weight ❹ . After the change, check
that the pin has completely entered the groove. At
the same time, check whether eccentric pin ❺ has
completely entered up to the end.
When the pin is excessively pressed, abnormal noise
or worn-up will be caused.
Results of Improper adjustment
◦ In case of the thick materials,
the stroke is changed. However,
basically, use the machine with
the standard stroke.
◦ When the needle bar stroke is
increased, needle heat or sew-
ing trouble mat occur.
◦ When the needle bar stroke is
increased, reduce the sewing
speed for use.
Good result is obtained from the
viewpoint of durability.
– 55 –