Hello Tony,
Are you sure you are looking at the stitch length ? usually the stitch length will go up to at least 5mm, easy mistake to make, if you are sure then make sure you have the pressure dial up to about 4 and make sure you have not dropped the teeth down by mistake, providing your machine is sewing zig zag perfectly you should not need to adjust anything internally, have you taken the throat plate off lately and put it back on properly ? another easy mistake to make, any further problems you are welcome to contact me.
Ken, drivewithken@blueyonder.co.uk
Ken Dourof
April 2007