The 15-88 is a treadle machine, and the 15-89 is a hand crank machine. They have larger and spoked handwheels.
The 15-90 has a regular sewing machine motor with a belt, and the 15-91 has the potted motor, which is a gear drive. They have smaller solid handwheels.

Yes, the needle is facing left. I'm not 100% sure I have the thread correctly threaded through the disc area. It doesn't seem to pull up on that spring. Also there is a slight (ever so slight) hesitation when I turn the flywheel. It will definitely turn all the way, but it's not smooth as silk.

thanks Mark - it has a belt - sure of that because it needed replacing!

If that machine came into my shop I would take that tension apart and clean all the old oil, rust, lint off. Then I would put that all back together using this manual: http://www.tfsr.org/publications/tec...achine_manual/ as a guide. If you follow their directions step by step you will be ok. I would also pull the bobbin, bobbin case and the stuff in there out using the same manual or probably about any owner's manual as a guide so you can get it all back together. Then I would take apart the bobbin case, clean it and adjust it. Then I would oil the working parts of the machine turn the machine as you go. You will need to oil everything that has a friction point. My oil of preference is Tri-Flow and Kroil if needed. I know there are people who only use sewing machine oil and some that think transmission oil is wonderful but I'm not trying to start any arguments. But use something that can be cleaned up. Parts can be found at your sewing machine shop or on line. You should check an owner's manual for that specific machine to know which way the needle goes and which way the thread goes.

you can download a manual for free from UK Singer or ISMAC. The 15-88/15-89 are needle flat to left, thread from right to left. There is a little wire thread guide right under the needle clamp. I'm not sure if it was mentioned above, but I'd definitely remove the needle plate and clean the lint out in that area (feed dogs, etc) while I was at it. the belt is a Singer #193066 available many places, incl online. These are great machines, and IMHO one of the best ones to start with. Let us know how it goes! Actually, it might be a different belt, depending on what motor and bracket combination has been installed on it.

Thank you all for your valuable feedback. I did clean the machine and oil it back in the winter, but was "all kinds of scared" to take the tension parts out, lest I be unable to get it all back in correctly. I have the manual and I've also been on the ISMACS site.

I have learned more than I ever thought I needed to know, but apparently have a ways to go, and I suppose that fear is my biggest hurdle. Fear of screwing it up worse or needing a professional. I only paid $50 for the machine in a cabinet (which looked nearly new and was chock full of notions and attachments) but then paid my SMG to rewire it and some other stuff (I told him I'd clean it). He charged $93.

I should have asked him to get it running, not just rewired; who knew they weren't the same thing?? LOL. Now I do . While cleaning and oiling it the first time, I lost a screw to the needle clamp assembly and had to order a whole new assembly (like 6 bucks). So I'm $150 into this thing and still can't use it. I wish I loved all thing mechanical; I am impatient and machines take some patience, don't they?

I am afraid something might be wrong that I can't fix myself, and my husband has zero interest in touching it. Last time he was putting the machine back onto the set screws, he was laying under it and accidentally dropped the screwdriver--which flippped, point first--into his nose. It bled like a massacre and I was not home at the time. It could have been his EYE! But he doesn't want to spend another dime or hour on it or chance losing a body part to this old thing when I "already have two perfectly good machines already"-- so I really want things to go smoothly for me if I have to go it alone.

I just got a 15-91 I have about 15 vintage machines cause they make the best patchwork. But I think the 15-91 is the best of all of them. It does have a quricky bobbin holder . The thread comes across the holder and out thru a little hole .
It took me a while to figure it out.

I checked out that online UK manual . I did not see diagrams specific to the 91. Will the info for the 99 be the same ?

Misled you I guess. Look on ISMAC. http://www.ismacs.net/free-sewing-ma...uals-list.html

Here is a link to a pdf version of the 15-91 manual from the Singerco.com website.

http://www.singerco.com/uploads/down...54a175ca4c.pdf