Necchi Lydia 3 Model 544 Not Sewing Properly

Question

I recently bought this machine from Goodwill and it is in excellent, very clean condition both inside and out so it has been well cared for.My problem is that it appears to be sort of "stuck" when it sews.The bottom tension and stitch looks fine but the top stitch seems to stitch in place and the material does not move through the machine without my help. The top stitch appears to be a very tiny zig zag but I have the machine set on straight stitch. I have taken the cover off and inspected the stitch selector/cam shaft thing and it appears to be moving correctly.I have also checked that the pressure foot is correctly attached.I have put a new needle in the machine and checked the diagrams at sewusa.com to ensure that I have threaded the top thread and the bobbin thread correctly. They all appear to be correct.I have the top tension set at 5-6 and stitch width at 4. I'm not sure how to adjust the bottom tension or if that would be necessary as it appears that the bottom stitch is o.k. The stitch selector is on straight stitch according to the stitch selector k**b and the little view window thing on the front of the machine.As I don't have a manual for this machine I am sort of working blind. I would love to have this machine up and running properly as it is a beautifully solid machine and appears to be of a quality not often found today.