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[Nico619]

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:

PROBLEM:

Any idea on the solution for this problem? Thanks

[WILD BILL]

Not that I can help but is it a clutched motor or servo?

[Nico619]

It's a clutch motor.

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:

Any ideas?

[Nico619]

I think I have finally solved the problem!

I'm not sure what exactly was causing it, but I mainly did two things:

-I rethreaded the whole machine. I had already threaded it in the past with no problem, but maybe this time something was wrong with it and rethreading it solved a tension problem.

-I had noticed that the roller foot was slightly in the way of the needle, causing it to infinitesimally bent. So i added a washer to have the roller foot move slightly to the left, to avoid being in the way of the needle.

-I also added some oil in the machine. It was supposed to be already oiled, and it probably was, however I added some more in case that was the problem.



I ran a few tests with various thicknesses of leather and so far i haven't gotten this problem again.



Thank you anyway for taking the time to read it this far!

[WILD BILL]

Glad you figured it out.

I don't know about that machine (or any others LOL) but I was told when I got mine to oil every spot before each use.

[JimmieJoe]

Looking at the rust on the machine I would have guessed oil to start with unless you have sufficient time on the machine with proper oiling so that the parts have become polished again.

I have a Neechi that was stiffened up when received, but after a good oiling and some run time it now runs smooth and effortless.

[Nico619]

Well, you may be right. The reason why i didn't give it much importance is because i was told by the previous owner that it was recently oiled, so i thought everything was already ready to go. Who knows if that was the problem.. I'm just glad it got fixed :D

[JimmieJoe]

You should oil the machine before every use until you get it running smoothly. Once it is running smoothly the oil will stick around longer, but some of the oil wells will be empty after sitting over night.
Non self oiling machine need to be reoil after 8 hours.