Bought my daughter a Schwinn S-500 a year ago. She loves it. The Chain got jammed and I had to take the back wheel off to get it free, I guess the chain got loose. After putting it back together, for some reason the sprockets don't seem to lign up. The chain will jam again if used. I know it is back together correctly. It almost looks as if the sprocket on the motor is to far in. Anybody have any ideas??