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17. TROUBLESHOOTING
Problem
6. Uneven seam
7. Upper thread breaks
115
Is the needle and feed timing correct?
Adjust the needle and feed timing.
Is the feed dog height correct?
Adjust the feed dog height so that it is 0.5 mm when the feed dog is at its
highest position.
Is the presser foot pressure too weak?
Adjust the presser foot pressure.
Is the needle bent or is the needle tip broken?
Replace the needle if it is bent or broken.
Is the needle scratched?
Replace the needle.
Is the needle properly installed?
If it is incorrect, install the needle correctly.
Is the needle too thin or too thick for the thread?
Replace with a needle which is suitable for the thread.
Is the upper thread tension too strong or to weak?
Adjust the upper thread tension.
Is the tension of the thread take-up spring too strong or too weak?
Adjust the tension of the thread take-up spring.
Is the operating range for the thread take-up spring too large or too small?
Decrease or increase the operating range for the thread take-up spring.
Is the thread path not smooth enough?
Use a file with a fine grain or sandpaper to polish smooth the thread path.
Is the rotary hook tip broken or worn?
Sharpen the rotary hook tip or replace the rotary hook.
Is the rotary hook thread path damaged?
Smooth the rotary hook thread path or replace the rotary hook.
Is the clearance between the needle plate and the inner rotary hook stop-
per correct?
Adjust the position of the opener.
Has the needle been pushed in fully during installation?
Install the needle correctly.
Is the height of the needle bar too low?
Adjust the height of the needle bar.
Is the needle and rotary hook timing correct?
After adjusting the needle bar height, adjust the needle and rotary hook
timing.
Is the sewing speed too fast, causing the thread to break due to heat?
Reduce the sewing machine speed.
Is the material feeding correctly at sections where the thickness changes
(such as joints and pockets)?
Increase the presser foot pressure.
LS2-B891, LT2-B892
Possible cause
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Motor Instruc-
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