301 looping on back
 

I have done numerous tension adjustments,changed needles, changed thread. If I sew slowly it has great stitching, front and back, if I run the machine fast I get a lot of looping on the back. Has anyone had a similar problem with their 301

Only if I overfill the bobbin and the thread slips out of the slot in the bobbin holder. Have you 1) cleaned the tension disks with crochet cotton or dental floss 2)cleaned out the lint in the bobbin area? A dirty machine will do strange things. You have to remove the two screws in the needleplate to really clean it underneath. Be sure to put the little hook back between the groove in the plate before tightening the screws. Do you have a manual - good cleaning instructions there?

http://www.quiltingboard.com/vintage...s-t170748.html
I made a post a while ago about tensions - maybe something on there will help