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17. TROUBLESHOOTING
Problem
4. Skipped stitches at sewing
start
Thread unravelling at
sewing start
Upper
thread
113
Is the bobbin turning smoothly?
Pull out the lower thread to check the turning of the bobbin, and replace the
bobbin if necessary.
Is the inner rotary hook tension spring defective?
Replace the rotary hook.
Is the bobbin racing?
Pull the anti-racing spring up or down to increase the spring tension, or
replace the anti-racing spring.
Is the rotary hook scratched?
Replace the rotary hook.
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 needle and feed timing correct?
Adjust the needle and feed timing.
Is the needle and rotary hook timing correct?
After adjusting the needle bar height, adjust the needle and rotary hook
timing.
Is the clearance between the needle plate and the inner rotary hook stop-
per correct?
Adjust the position of the opener.
Is the rotary hook lubrication amount too small?
If the oil level has dropped to the lower reference line on the oil gauge, add
more oil.
Adjust the rotary hook lubrication amount.
Is there any rubbish sticking to the rear of the inner rotary hook?
Clean the inner rotary hook.
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.
Are the thread take-up spring tensions too strong?
Reduce the tension of the thread take-up springs.
Is the operating range for the thread take-up spring too large?
Decrease the operating range for the thread take-up spring.
Is the presser foot pressure too weak?
Adjust the presser foot pressure.
Is the needle too wide?
Try using a needle with a count that is one lower than the current needle.
〈-005 specifications〉
Is the thread take-up lever at its highest position at the sewing start?
Set the thread take-up lever to its highest position at the sewing start.
Is the length of the upper thread trailing from the needle hole too short?
Pull about 50 mm of thread through the needle hole at the sewing start.
LS2-B891, LT2-B892
Possible cause
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