Could the motor smell hot because some oil got in there or on a belt? or Does the motor just need to be cleaned? I bought one once that I'd swear someone oiled the motor. It had to be taken down and really cleaned before it quit smelling funny and running bad. It's now the Singer 403 I use the most. It was like new in appearance when I got it but someone had REALLY oiled her up to sell it. She had set around a long time and wasn't moving. People sometimes think if she doesn't move her motor is not working. It was more like all kinds of dried on oil inside her over the years. Once she was cleaned she was virtually a new machine. Those old Singer 400 & 500s do NOT like dried on oil. If the dial doesn't work chances are it is dried on oil. However I have one that has a very obvious bent stitch selector shaft. I need to get my donor machine out and do a transplant. I'm just not sure if a Singer 500 will match up with a Singer 401 stitch selector shaft without taking them both out.