I think others have given you the likely culprit- to be sure the machine is taken off the bobbin winding mode. Second possibility is a belt is slipping that needs to be replaced. The older Kenmores are great reliable machines. Cams are fairly easy to find online. There are a couple different Kenmore cam styles so be sure to order the ones compatible with your machine. Hopefully you can download the manual from the Sears site. If you can't just pm me. I don't think I have the specific one, but many Kenmore models have similar features. Enjoy your machine!