Hello Deborah,
If you have been through absolutely everything try one more thing for me,press up and down on the reverse lever whilst looking at the teeth, they should move slightly backwards, if they do then the mechanism is working okay and the only possible thing it could be is the feeding cam on the top of the machine shaft has moved, very unsual but it can happen, if you take the top cover off the machine and look at the top main shaft you will see a long bar going downwards and the top part looks like a two pronged fork, the two pronged fork bit fits over a cam on the main shaft, that cam if you look to the side of it should have a line which corresponds to a mark on the main shaft that is called a timing mark and they should be in line, if they are not you have to slacken the screw on the cam and move it slightly, sometimes you may even have to move it slightly past the the timing mark on the shaft, trial and error but it is the only thing that will adjust the feed, there is nothing else, once you have moved the cam give it a quick test, any problems let me know.
Ken
drivewithken@blueyonder.co.uk
July 2007