Problem Cause ; Remedy ; Upper thread is not - Page 150

10. TROUBLESHOOTING 

BAS-311G, BAS-326G 

143

Problem Cause 

Remedy 

Reference

Movable knife is not cutting cleanly. 

Replace with a new one. 

P. 95 

Fixed knife is not cutting cleanly. 

Sharpen the fixed knife or replace it 
with a new one. 

P. 95 

Adjust the position of the shuttle race 
thread guide. 

P. 92 

Movable knife is not picking up the 
upper thread. 

Adjust the needle bar lift amount. 

P. 91 

Movable knife is not picking up the 
upper thread because the last stitch is 
being skipped. 

Refer to "Skipped stitches occur". 

P. 142 

Movable knife position is incorrect. 

Adjust the position of the movable 
knife. 

P. 93 
P. 94 

Upper thread is not 
trimmed. 

Sub-tension is too weak. 

Turn the sub-tension nut to adjust the 
tension. 

Instruction 

manual

Shuttle race thread guide is not 
separating the threads enough. 

Adjust the position of the shuttle race 
thread guide. 

P. 92 

Incorrect tightening of the upper thread

Adjust the upper thread tension. 

P. 89 

Poor stitch finish on 
underside of material. 

Upper thread length is irregular. 

Adjust the sub-tension. 

Instruction 

manual

Upper thread tension is too weak. 

Adjust the upper thread tension. 

P. 89 

Lower thread tension is too weak. 

Adjust the lower thread tension. 

P. 89 

Thread take-up spring tension and 
height are incorrect. 

Adjust the tension and height of the 
thread take-up spring. 

P. 90 

Incorrect tightening of 
the thread 

Position of arm thread guide R is 
incorrect. 

Adjust the position of arm thread guide 
R. 

P. 90 

Thread take-up spring tension and 
height are incorrect. 

Adjust the tension and height of the 
thread take-up spring. 

P. 90 

Sub-tension is too weak. 

Turn the sub-tension nut to adjust the 
tension. 

Instruction 

manual

Upper thread length is 
irregular. 

Fixed knife is not cutting cleanly. 

Sharpen the fixed knife or replace it 
with a new one. 

P. 95 

Check if the machine head switch cord 
is disconnected. 

Instruction 

manual

Adjust the position of the machine head 
switch. 

P. 88 

Sewing machine does 
not operate when the 
power is turned on and 
the foot switch is 
depressed. 

Machine head switch does not work. 

If the machine head switch is 
malfunctioning, replace it with a new 
one.