Both of the above replies have merit and in many cases are true. Having over 25 of these machines the first in 1976. I have come across only one machine that exhibited this problem. At the request of the dealer and new owner I diagnosed the problem as tight clearances on the hook and race. I used valve compound, a greasy abrasive paste and coated the components while running machine to polish and increase clearances. This worked but I don't think that machine would sew heavier than #92. Another issue is bobbin thepositioner escapment could need adjustment.
