Juki MO-644 Sewing Machine Service Manual (Model MO-644) - 2 Pages. Lost your sewing machine's service manual? We've got you covered! This service manual is the ultimate guide to unlock the full potential of your Juki MO-644. No more confusion or frustration—just clear, concise instructions right at your fingertips. What's inside? Everything you need to know from tension control to adjustments.