Hello, I recently bought a Necchi 910-159 sewing machine (should be a pfaff 191 copy), and for some reason sometimes when i start sewing, slowly pressing the pedal, it doesn't start, and you can hear the motor becoming louder and louder, almost as if it's too hard for it to go through the leather. But the thing is that the needle hasn't even moved from the top position, so it's not because of that...
I'll post two videos, one in which the sewing machine works normally, and another one in which it gets stuck. After hearing the motor becoming louder it suddenly starts sewing at full speed, which is the problem i want to solve..
NO PROBLEM: https://imgur.com/a/0YczOWe
PROBLEM: https://imgur.com/a/RJD4sCs
I've analized the sewing machine in the past few hours and i think i might have found what causes the problem.
I first noticed that it was not a motor problem: the increasing sound is caused by the bobbin being jammed by the thread.
Now, at first i thought it was the bobbin thread, being not properly winded or something along those lines. However after a few tests and rewindings i started noticing that it probably was the upper thread..
I then used two threads of different colors, and as i assumed, it was the upper thread which for some reason winds around the bobbin case, causing this jamming which causes that sound by the motor, since it can't freely move the lower thread.
The super fast sewing right after that happens because, i assume, the motor is finally able to break the jammed thread and sews at full speed...
So now i'm pretty sure this is the explanation, however i have no idea how to solve this upper thread jamming around the bobbin case.
here is a video of the upper thread getting stuck: https://imgur.com/a/WU6zqsl