You could try typing in the model number and Google it. There is a website I found and printed out a schematic of a machine for a friend (tntrepair.com). Her machine wouldn't go in reverse but she didn't realize she couldn't adjust the stitch length either. I was able to purchase the part and fix it for her. I checked that site, but didn't find the 242. I did however find instructions for threading the machine at sewusa.com. It could be how the bobbin is loaded (bobbin instructions on sewusa.com too)or if there is lint in there from the previous owner. You could carefully take the bobbin race out and use a vacuum to suck out the lint. That is tricky and you have to be sure everything goes back the way it came out!
Hope someone can help you.