First turn the machine by hand to observe whether the looper cannot hook the needle thread loop or the machine needle does not insert the looper triangle thread loop, and then check and adjust according to the following suggestions.
(1) The needle guard should be adjusted reliably, neither too close nor too far.
(2) The curved needle should pass through while rubbing the straight needle.
(3) Adjust the looper faster.
(4) Tighten the needle thread on the left to the point.
