My machine was working fine until recently (when I had to have the foot fixed). I tried it. It started to sew, then the bottom thread knotted up. I changed the needle, cleaned out the bobbin casing, cleaned any dust. It now does not pick up the lower bobbin thread, so I cannot sew.
Glad you managed to fix it yourself, in addition to the 250kms I would guess the cost would have been a lot.
Posted on Apr 01, 2008
Pre-tension disk 
Bobbin winder shaft 
Bobbin
Pre-tension disk 
Pulling it in as far as possible
Spring on the shaft 
Groove of the bobbin
Sewing speed controller
Wound evenly 
Wound poorly331 views
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I have solved the problem. I realised that the needle shaft must have moved up slightly when I tried to move the needle from the knotted thread. I noticed that the needle head did not drop low enough for the thread to be caught by the hook in the bobbin area - there are some really good diagrams of this on sewusa.com. I removed the side casing (a screw is on the left side of the machine). There is a small screw on the needle shaft which requires a small torx screwdriver. I loosened this screw slightly and the needle shaft dropped a bit. I carefull lowered the needle into position - I did not mark the shaft, and wanted to make sure that the needle shaft was not too low, otherwise when the needle lowered it would catch on the hook and damage it. It seemed ok, I tightened the screw on the shaft, and so far it seems to be working. Normally I would have taken it to a technician, but for me that would involve driving about 250 kms!!
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