Change your needle, use a good quality one and it might work better. I have the exact same problem with my machines and it's usually because I have an dull needle. I tend to be a member of the "oh, needles need to be changed? I just sew until they break" club. And I would buy the cheapy needles whenever I'd come across them. I once found a store that had 4 packs of 5 needles for $1.00. Just a few years ago, I found out why they were so cheap. Oh well lessons learned. Leaders and enders are a great way to assist with the problem also.