My Singer 201 sewing machine has been sewing beautifully - until today. For no apparent reason the bobbin stitch sews fine on the surface, but the underneath is a mess of loose threads and stitches. Eventually the thread breaks and needs re-threading. I have tried sorting the tension, re threading the bobbin and the top thread. It all defeats me - any answers please

Moseley, November 2013

first thing is change needle and then you must make sure tension is correct by pulling thread thru tension disc and asserten there is tension,same goes for boobin tesion as sometimes there is dirt trapped between tension discs or tension spring

johan, November 2013