I'm trying to trouble shoot my Singer 301. I got my bobbin case and finally got some bobbins and was able to test it out today. I can stitch fine in while going slow, med. is fine, but if I give it the gas and try to stitch fast the top thread breaks. I've lowered the tension and nothing seems to help. I've double checked my threading and replaced the needle correctly. Maybe there's a burr I can't see in the hook? I didn't really have time to investigate as it's my daughter's b-day party this evening. I'm happy my 301 sews, but it's not "right" so my detective hat will be on. Anyone have any suggestions? I don't think the timing would have something to do with this, but maybe?