Go to http://www.tandtrepair.com/StylistLine.html. If you click on the button for the 478 schematic you can download the 5 page parts listing, save it on a CD or HD, and print it out to keep a copy. Then, when you ask a question, you can supply the actual part number of that gear in your question.
I don't know how much traffic there is here, but that part number listing will be very useful when you do find someone who knows how to do it. Google for the part number for other help or parts source.
Note there are repair manuals for sale, and you can locate them via Google as well. http://www.sewusa.com/Sewing_Machine_Manuals/Singer_Repair_Manuals.htm says it has repair manuals, but the manuals actually seem only to cover minor problems and maintenance. There is a guide to problems when usingi the machine, which does not help you but would be helpful to new users.
Sorry I can't help you with detailed repair instructions.. My wife's has apparently jumped a cog on the lower belt and the needle hits part # 155474 (thingie that holds the bobbin holder).
That same URL sells a manual that tells how to adust timing on that drive belt which is part number #96137. We are not sure if the belt needs to be replaced, and if so, are such parts available.
My wife recently inherited in Mexico the treadle machine her grandmother got in 1910, manufactured in Elizabeth NJ. She oiled it up, and hemmed an entire bed sheet with it. Her aunt has a 1885 machine that still works perfectly as well.
Bruce McGovern
April 2007
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix sewing machines.