CowboyBob

This manual should work for you. Singer 51w100 and 52w100 - instructions for using and adjusting.pdf

Yes,the best thing to do is try to run it high speed (like winding a bobbin) once a day until you see oil @ the window & you shouldn't have any problems.I went to an Amishmans place once & he had a Singer 241 that had a buttonhole attachment on it that he ran for quite a few yrs w/o using the oil pan.

Use size 23 with 207.

When you shorten the stitch this machine like many others it will make the dial alot easier to go to a lower length by pushing the reverse lever down an inch.This takes the pressure off the dial.

Another cause,the motor belt many of them have bulge where they join you can feel it with your finger.Or it could too tight.And since you moved the balancer you should try to put it back the where it was so the #1 feed cam & #1 balancer screw line up.

Judging by the looks of it I'd say it hasn't been used a whole lot & for the price I'd buy it.

@Nico619#458 is a 3/16"x28

We have sold alot of these over the years approx 3000 or more & haven't seen any major problems with them yet!Yes,the feed mechanism is alittle different that the larger 3500 & 4500 .BUT this was made as a lower price machine to get people sewing for less $$.That's why it's limited to 1/2" of leather for less stress on the feed parts.

Yes,it will fit in the table BUT it uses a different knee lifter & might require on belt adjustment.

@ArtD I've sold alot of these over the years & never had a problem like this.If you haven't already you should try to lower the height the feet walk.

They won't work on this machine they are close to 10mm tall & you only have around 13mm foot lift.

@Damas The 441 pressure feet will interchange BUT both the needle plates & feed dog do not interchange with the 441 or the 205.I'm almost certain you can use the standard plate for all of your sewing needs.The only other plate that is available is a slotted one which requires removal of the feed dog,this is used for thinner leather.

All double needle machines need 2-bobbins(hooks) so you can't make a double needle out of it.if you did since it only has one bobbin, the stitch will look like a zig-zag on the bottom side,causing the thread to wear through quickly.

Here's a thread & needle size chart.https://tolindsewmach.com/thread-chart.html

Yes,your going in the right direction,birdnesting underneath is always the top thread.Either it's too loose or not threaded correctly,try tightening the top tension 1/2 turn @ a time until it goes away.