JUKI LU-2800 Series Engineer's Manual page 125

WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine.
Trouble
3. Needle thread trails 2 to 3 cm
from the wrong side of the fabric.
Cause
3-1) Needle thread tension is too low.
3-2) Thread take-up spring works exces-
sively or the stroke of the spring is too
small.
3-3) Feed timing is not proper.
3-4) Timing between the needle and the
hook is excessively advanced or
retarded.
3-5) Thread melts due to needle heat.
3-6) Amount of oil in the hook is exces-
sive.
* Use separately available parts below :
• 21144308
• B1114012000 Thread guide rod
• B91351230B0 Silicon oiler
Checking
4-A) Check the specified dimension.
6-A) Check the amount of oil in the
hook.
Needle thread lubricator
Corrective measures
Adjust the needle thread tension. (This trouble
occurs a lot when using synthetic threads.
Decrease the tension of of the thread take-up
spring and increase the stroke of the spring.
Refer to "2.-(8) Feed adjustment".
Refer to "2.-(6) Needle-to-hook timing".
Decrease the sewing speed.
Use silicon oil.
(Refer to * below.)
Adjust the amount of oil in the hook.
Refer to "2.-(15) Lubrication".