Thanks mickey. I've cleaned whole bobbin area, sorry but I used wd40 so will have to get oil into it. Also re wound a fresh bobbin. Running smoothly and not looping on bottom now. Stitch is almost tight enough. On the top it is perfect but the underneath bobbin stitch looks crooked/diagonal in places and looks ever so slightly loose. I've lose new bobbin screw about 90 degrees and increased needle tension. Thus has almost sorted it......anything else I can do?