Took stop motion knob off how do the pieces go

Question edited for clarity, 'make model (what it is)'.

Lots of general help below. Hopefully, you won't need parts.

The handwheel and the stop motion on a vintage Singer - part ...

oldsingersewingmachineblog.com https://oldsingersewingmachineblog.com > 2012/03/10
Mar 10, 2012 - If the stop screw will go all the way in, hold the handwheel and turn the knob clockwise as far as you can.

The handwheel on a vintage Singer and the stop motion - part ...

oldsingersewingmachineblog.com https://oldsingersewingmachineblog.com > 2012/03/05
Mar 5, 2012 - Now, if you replace the stop motion clamp screw (the chromed knob) and tighten it up, you're back to normal - rotation of the handwheel ...

Stuck Stop Motion Knob & Handwheel

The Singer Featherweight Shop https://singer-featherweight.com > blogs > schoolhouse
What is the best way to remove a stuck hand wheel. I am able to remove the stop motion knob but can seem to work the hand wheel off. I have put sewing ...

SINGER HANDWHEEL REPAIR on Andy Tube

YouTube · Andy Tube 31.8K+ followers · 6 months ago The Handwheel and Stop-Motion Mechanism of the Singer Model 353 Genie. Andy Tube · 31:45. Remove Handwheel, Motor Belt and Bobbin Winder Singer ...

The handwheel and the stop motion on a vintage Singer

Pinterest · Mommygita 11 years ago Following on from the last post, we'll now look at how to replace the handwheel, or if you like the balance wheel, which is a process that ...
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The web site below suggests a way to find the date of manufacture of a different model, so please check if you have the same option.

https://instappraisal.com/appraisal/nelco-sewing-machine-ja38

Quoting about a ja38:

"Submitted by tbrennan34 I DO know something that will help you! As it happens I also have one of these beautiful machines for sale... simply because no one here knows how to use the thing! LOL To find the manufacturing date simply open the flip top, then tip the small wooden trap door toward yourself as you would if you were going to use the machine. The date of manufacture is stamped on the underside. It's that simple!"

You cannot tighten the knob at all?

That is what was needed...they can bind over years of inactivity

What are you calling a stop motion knob? Are you trying to stop the needle from moving while winding a bobbin?

I would suggest that the machine needs to be serviced to find out why it not responding the way it should.

check with the sewvacdoctor.com & ask them about the manual

1 Release the stop-motion knob on the right side of the sewing machine by turning it oward you.2 Place a spool of thread of your choice on the spool pin located toward the back of the sewing machine.3 Pull thread from the spool through the threading knob on the top of the machine.4 Pull 2 to 3 inches of thread through one of the holes on the bobbin. Hand-wrap thread around the bobbin in an anti-clockwise direction five or six times.5 Place the wrapped bobbin on the bobbin spindle.6 Push the winder spindle to the right, against the stopper, and depress the foot pedal to begin winding.7 Wind bobbin until completed, then return winder spindle to its original position.8 Tighten the stop-motion knob.

There should be a washer that fits over the balance wheel, if you dont put that back on the machine wont work.
Check around and see if it fell off when you removed the knob, or check to see if it is stuck inside the knob.

The washer is about 1" in diameter with a couple little tabs on it.
It will only work when installed correctly so if at first you fail just turn the ****** over!