I bought a singer 5511. I had problems with it jamming also. I found that if a needle breaks there is a piece of needle stuck under the bobbin case. I also found that if your bobbin is not sitting in correctly it will cause it to jam. What i mean is if you drop your bobbin in to where your thread is going counter clockwise then have the thread hook onto the latch. That will solve your problem. Or it could be that your thread is not in the tension guide on top. The space between the top hook by the thread holder and the hook before the needle. That will cause it to jam. So far I am happy with my singer 5511. I actually can sew heavy duty fabric with it. I can sew up to half inch thick leather with it with no problems. I've had mine now for 11 years and is still going strong. Hope you solve the problem.